Just another story about world

3D effect in firefox

2010-05-25T20:30:00.000-07:00

1. www.foxtab.com visit to download the addon for firefox

2. click download now, and click allow on the top right corner as shown in the picture above, if it is. it will appear as follows, wait until the countdown timer is stopped and the install button visible, if it is. click the install button.

3. wait until the installation is complete, the downloaded file is relatively small, only about 500KB

4. if it has been successfully installed. click restart firefox button, as shown in the picture below.

5. congratulations, FoxTab already installed, to reactivate press ctrl + Q so that it appears like the following picture
beautiful isn't it?

Tested on: 03/06 @ ubuntu Forefox 10:04 (Lucid Lynx)

The Air Umbrella: Blown the rain away.

2010-03-27T03:19:00.000-07:00

For some odd reason, this brolly calls up an image of Obi-Wan Kenobi. However, this weather protector has nothing to do with Star Wars, though the unconventional concept taps the Force. We're talking about a steady stream of air that's sucked in from the bottom of the shaft and then released out the top. The result is an invisible canopy of air that shields you from the downpour.

Korean designer Je Sung Park claims you can adjust the size of the air curtain depending on the number of people using the umbrella, as well as the length of the handle. But to be completely honest, we're still grappling with the feasibility of this particular concept.

source : http://asia.cnet.com/crave/category/futuretech/2010/01/

GoDaddy, 1 heart with google?

2010-03-26T04:40:00.000-07:00

google have moved from china, now godaddy follow google's move to from china.

Two days after Google halted censorship in China, another leading US Internet company, Go Daddy, said it was cutting back on its activities there because of Chinese regulations.

Go Daddy, the largest Web domain name registrar in the world, is no longer registering names in China because of "chilling" new requirements imposed by the Chinese authorities, executive vice president Christine Jones said on Wednesday.

Jones also told a hearing of the Congressional-Executive Commission on China that Go Daddy was one of the companies hit by Chinese-based cyberattacks in December that contributed to Google's decision to stop self-censorship there.

Representative Chris Smith, a Republican from New Jersey, praised Google and Go Daddy at the hearing here for "doing the right thing in China" and urged other US companies, specifically Microsoft, to follow their lead.

"Google fired a shot heard 'round the world, and now a second American company has answered the call to defend the rights of the Chinese people," Smith said.

Google announced Monday it had effectively closed its Chinese-language search engine in China, Google.cn, and begun redirecting mainland Chinese users to an uncensored site in Hong Kong.

Chronology: Google's operations in China

Alan Davidson, Google's director of public policy, told the hearing the Hong Kong site is already being censored.

"We are well aware that the Chinese government can, at any time, block access to our services -- indeed we have already seen intermittent censorship of certain search queries on both Google.com.hk and Google.com," he said.

Davidson also echoed a call made by Google co-founder Sergey Brin for new rules to govern trade in the online world.

Brin said in an interview with the British newspaper The Guardian that Chinese regulations that prevent companies from being competitive in China should be considered a "trade barrier."

"Since services and information are our most successful exports, if regulations in China effectively prevent us from being competitive, then they are a trade barrier," Brin said.

Davidson said governments "need to develop a full set of new trade rules to address new trade barriers.

"We should continue to look for effective ways to address unfair foreign trade barriers in the online world: to use trade agreements, trade tools, and trade diplomacy to promote the free flow of information on the Internet."

Brin and Davidson's comments came after TOM Online, the Internet company owned by Hong Kong's richest man, Li Ka-shing, severed ties with Google.

TOM, which runs online and mobile Internet services in mainland China, said that "as a Chinese company, we adhere to rules and regulations in China where we operate our businesses."

TOM's move sparked concerns other companies may also pull away from the Web giant. On Thursday the Financial Times reported that China Unicom, the country's second largest mobile phone operator, will jettison Google's search function from new handsets.

The move is the first concrete result of Google's decision to shut down its Chinese search engine on Monday.

"We are willing to work with any company that abides by Chinese law.... We don't have any cooperation with Google currently," the Financial Times quoted China Unicom president Lu Yimin as saying.

China has attacked Google for stopping censorship but said there should be no broader fall-out in Sino-US ties provided the issue is not politicized in the United States.

Go Daddy's Jones said the company has been authorized since April 2005 by the China Internet Network Information Centre (CNNIC) to offer registration services for .cn domain names.

The .cn suffix is a Top Level Domain for China like .com and individuals or companies seeking to create a Web address are required to go through a registrar such as Go Daddy, which has 40 million domain names under management.

Jones said Go Daddy collects contact information of individuals or companies registering a domain name including their full name, address, telephone number and email address.

Four months ago, however, CNNIC required registrants of new .cn names to provide color headshot photos, a Chinese business registration number and signed registration forms, she said.

She said Go Daddy is "concerned for the security of the individuals affected by CNNIC's new requirements, as well as for the chilling effect we believe the requirements will have on new .cn domain name registrations.

"For these reasons, we have decided to discontinue offering new .cn domain names at this time," Jones said. "We didn't want to act as an agent of the Chinese government."

Jones also said that Go Daddy was one of more than 30 companies hit by the cyberattacks in December that Google said originated in China. "We've had a couple of dozen since the first of the year as well," she said.

"The Google attack was aimed at infiltrating email accounts," she said. "The attack on our system is designed to disable websites somebody doesn't like."
Source: The Jakataglobe

Two days after Google (GOOG) closed its China-based search engine, the world's largest domain registrar has followed suit. GoDaddy announced it will no longer register domains from within the world's largest country.

GoDaddy's actions come after the China Internet Network Information Center (CNNIC) issued rules requiring domain applicants to submit detailed personal information, including color headshots. The company said it will stop offering .cn registrations -- the top-level domain used in China.

"We are concerned for the security of the individuals affected by CNNIC's new requirements, as well as for the chilling effect we believe the requirements will have on new .CN domain name registrations," GoDaddy said in a statement. "For these reasons, we have decided to discontinue offering new .cn domain names at this time. We continue to manage the .cn domain names of our existing customers."

Human rights activists hope that GoDaddy's move will initiate a stream of Western companies to follow Google's lead in pulling out of the market. Google said Monday that it will close its China-based search engine and redirect users to a site based in Hong Kong (see Timeline: Google's Dispute with China Came Down to Principle).

New Chinese Rules

GoDaddy objected in particular to rules put in place in December by the state-affiliated CNNIC requiring domain applicants to submit detailed personal information. The company drew praise from U.S. lawmakers during a hearing Wednesday to address Google's dispute with China.

"GoDaddy is the first company to publicly follow Google's example in responding to the Chinese government's censorship of the Internet by partially retreating from the Chinese market," said Rep. Christopher H. Smith (R.-N.J.) in a statement. "Google fired a shot heard 'round the world, and now a second American company has answered the call to defend the rights of the Chinese people."

Arvind Ganesan, business and human rights director at Human Rights Watch, told The Washington Post that the new rules are designed to further tighten China's grip on informtation on the internet. "The underlying intent is, if you're engaging in political speech, we want to know who's engaging in it and what Web site is behind it," Ganesan told the Post. "This is a way the Chinese government can send a chilling message to people that they shouldn't speak freely online. It's forcing us companies to be both the censor and the spy on behalf of the Chinese government."

Multiple Cyber Attacks

GoDaddy says it's been the target of multiple cyber attacks orginating in China. Testifying before Congress Wednesday, Christine Jones, GoDaddy executive v.p. and general counsel, said, "Most of the attacks on our system are designed to disable the websites of our customers. And those tend to be human rights sites, Tiananmen Square anniversary sites, or weblogs that discuss Tibetan monks. Anything that the Chinese government deems inappropriate."

The company's move was independent of Google's, Jones said: "We just made a decision we didn't want to act as an agent of the Chinese government." China, Jones added, "rarely asks us to shut down counterfeit goods or other IP violations, because frankly, I think they support that."

source: dailyfinance

Google, China, and Hongkong

2010-03-26T02:54:00.000-07:00

KOMPAS.com - Google said Tuesday that it may pull out of China because of a sophisticated computer network attack originating in China and targeting its e-mail service.

The company said it had evidence to suggest that "a primary goal of the attackers was accessing the Gmail accounts" of Chinese human rights activists. The attack was discovered in December.

Based on its investigation to date, Google said it does not believe the cyber attack succeeded. "Only two Gmail accounts appear to have been accessed, and that activity was limited to account information (such as the date the account was created) and subject line, rather than the content of emails themselves," the company said in a blog posting.

But David Drummond, Google senior vice president and chief legal officer, added that the attacks "have led us to conclude that we should review the feasibility of our business operations in China."

Google has further decided it is no longer willing to continue censoring its search results in Chinese Google sites, Drummond said, and over the next few weeks it will discuss with the Beijing government how it may operate "an unfiltered search engine within the law, if at all," he said.

"We recognize that this may well mean having to shut down Google.cn, and potentially our offices in China," he said.

Privacy advocates applauded Google's move to disclose the attack and reverse its stand on censorship of its China search engine results.

"Google has taken a bold and difficult step for Internet freedom in support of fundamental human rights," said Center for Democracy & Technology president Leslie Harris. "No company should be forced to operate under government threat to its core values or to the rights and safety of its users. We support Google for being willing to engage in this very difficult process."

At least 20 other large companies have been similarly targeted with such attacks, Google said. The firms' industries range from finance and technology to media and chemicals.

"We have taken the unusual step of sharing information about these attacks with a broad audience not just because of the security and human rights implications of what we have unearthed, but also because this information goes to the heart of a much bigger global debate about freedom of speech," Drummond said.

In a separate development, Google officials said, the company discovered that the Gmail accounts of dozens of China human rights advocates in the United States, China and Europe "appear to have been routinely accessed by third parties." The hacking occurred most likely through phishing scams -- luring users to download malicious software by opening innocent-looking e-mails -- or malware placed on users' computers, rather than by breaking into Google's corporate infrastructure, the company said.

China is among a handful of countries considered to have impressive cyber offensive capabilities, but U.S. officials have refrained from publicly accusing the country because determining with certainty who is behind an attack is quite difficult.

Attacks against China rights activists have been growing, however, and suspicion has fallen on the Beijing government or its broad army of proxies.

When Google set up a subsidiary in China in 2005 and purchased servers hosted in the country, it agreed to censor its search results. But the company and the government officials trolling the Internet have continued to clash over what content should be blocked.

The conflicts escalated in June when Beijing blamed Google for smut on the Internet, saying that some search results could be considered pornographic. The government ordered Google to halt foreign Web searches. Many Chinese bloggers pointed out that Chinese search engines would produce the same results but only the foreign company was singled out for blame in headlines in the state-run People's Daily and New China News Service.

That same month China temporarily blocked Google.com and Gmail in what was believed to be a punishment.

The U.S, government, working with Congress, seems to be slowly moving toward a policy to attempt to deal with this new threat to freedom of expression. Congress recently passed the Iran Voice Act, which has provisions that require the government to investigate companies that may have helped Iran to conduct surveillance online.

The State Department has allocated funds to companies to help get around Internet firewalls put up by China and other countries, although there is some controversy over those funds because one of the most successful outfits that does that kind of work is run by members of the Falun Gong sect, which is banned in China. The Global Internet Freedom Consortium has yet to receive significant, if any, government funding.

"The Chinese would go ballistic if we did that," said one U.S. official.

Secretary of State Hillary Rodham Clinton is scheduled to give a speech on Internet freedom next week.

Source: Kompas

China angry at Google move to Hong Kong

China has criticised Google's decision to stop censoring its China-based search engine, calling the move "totally wrong" and accusing the company of violating promises.More than two months after it threatened to shut down Google.cn if it had to continue policing the site, the company made the shift early on Tuesday.

Visitors to Google.cn are automatically redirected to the Chinese-language service based in Hong Kong, where Google is not required to censor searches.

The State Council Information Office, which oversees the internet said: "Google has violated its written promise it made when entering the Chinese market by stopping filtering its searching service and blaming China in insinuation for alleged hacker attacks."

"This is totally wrong. We're uncompromisingly opposed to the politicisation of commercial issues, and express our discontent and indignation to Google for its unreasonable accusations and conducts."

Goggle's Hong Kong page heralded the shift, with the words "Welcome to Google Search in China's new home."

The move, in effect, shifts the responsibility for censoring from Google to the communist government, which operates an extensive monitoring and filtering system to block content, deemed unacceptable. Users in China were unable to retrieve searches on sensitive topics.

The Chinese government could retaliate by blocking access to Google's services, much as it has completely shut off YouTube, Facebook and Twitter. China has an estimated 350 million Internet users.

source: uk.news.yahoo.com

Underwater River, a river of hydrogen sulphide ?

2010-03-12T03:13:00.000-08:00

Have you seen an underwater river?. you can see this phenomenon in Cenote Angelita cave in Mexico. at a depth of more than 30 yards a team of divers to find fresh water in the middle of the ocean water column. Conditions changed and divers returned to find the sea water began to pass 60 meters depth. A few yards from the site will find a cave. At the bottom of the cave diving team discovered a river complete with trees and leaves that float in the water column. hmm, a tree and leaves?.

But wait. it isn't a river, However, the atmosphere was like a river complete with a layer of such colored water slightly brown. The brown water that's look like a river is came from Hydrogen Sulfide, Gas usually produced from sewage channels.

“We are 30 meters deep, fresh water, then 60 meters deep – salty water and under me I see a river, island and fallen leaves… Actually, the river, which you can see, is a layer of hydrogen sulphide.” says Anatoly Beloshchin a professional photographer who dive in that cave.

Privacy Policy

2010-03-09T19:32:00.000-08:00

Privacy Policy for www.ferizkurniawan.blogspot.com

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Porsche 918 Spyder Concept, Fast Hybrid Car

2010-03-02T22:44:00.000-08:00

Who said green cars can’t be mean? Not Porsche. On the eve of the Geneva Auto Show, the Stuttgart-based company took the wraps off the 918 Spyder Concept, a 2-seat mid-engine supercar with hybrid and electric drive technology.

Just how fast is this thing? Well, Porsche says the 918 Spyder Concept hits 100 km/h (62 mph) in less than 3.2 seconds, and it blasts to a top speed of 198 mph. Not only that, it laps the Nürburgring in less than 7 minutes 30 seconds, which means it’s even faster than the hallowed Carrera GT.

Just how green is it? Porsche says that, when driven accordingly, the plug-in hybrid 918 Spyder Concept gets an outstanding 78 mpg, with an emissions level of just 70 grams of C02 per kilometer.

The 918 Spyder Concept is powered by a high-revving V-8 related to the 3.4-liter in the Porsche RS Spyder racing car. In 918 Spyder form, this mid-mounted engine revs to 9200 rpm and produces more than 500 bhp. Electric motors at the front and rear axles add an additional 218 horsepower to the output. The V-8’s power, and that of the rear electric motor, reaches the Spyder Concept’s rear wheels via a 7-speed PDK gearbox. The drive to the front wheels is pure electric, via a fixed ratio. The liquid-cooled lithium-ion battery pack behind the cockpit can be charged at home, or by brake regeneration.

Porsche 918 Spyder Concept

Four distinct driving modes are available. E Drive is solely electric power, with a range of up to 16 miles. In Hybrid mode, electric power and gasoline power are used as conditions warrant, in ways designed to maximize economy or performance. In Sport Hybrid mode, in which both drive systems maximize performance, most of the power goes rearward, aided by torque vectoring to help the car’s dynamics. Lastly, there’s Race Hybrid mode for the utmost performance, such as running at the limit on the racetrack. In this mode, there’s even a “push to pass” E-Boost feature that feeds in added electrical power for overtaking… or better lap times.

The 918 Spyder’s modular chassis is made of CFP (carbon-fiber-reinforced plastic), while Porsche has also employed lots of magnesium and aluminum to keep the car’s weight down to a reasonably svelte 3285 lb. Aesthetically, the 918 Spyder looks very much like a relative of the Carrera GT. It also looks like it would be perfectly at home on the road or the track. Variable aerodynamics, especially around the rear spoiler, are necessary in a car with such a fast top speed, and the rear hoods extending back from the headrests accommodate retractable air intakes that provide a ram-air function.

Porsche says the interior of the 918 Spyder Concept offers a glimpse of the future, and we’re glad that it remains driver-oriented with circular dial gauges. On the left is one for road speed; in the middle is engine speed (right where it belongs); and on the right is the energy-management gauge. Modernity is addressed via the center console, which has a touch screen for what Porsche calls “intuitive” control of the car’s functions.

Lastly, the 918 Spyder Concept is fitted with a Range Manager. Using the map in the satellite navigation system, the Range Manager displays the remaining range the Spyder is able to cover. And in cities, it will tell you if you can reach your destination on electric power alone. Just the thing to make sure you arrive at the Nürburgring with a full tank.

We admit the Porsche 918 Spyder Concept took us by surprise at Geneva. But we very much like what we see, and the fact that this Porsche has lapped the Nürburgring proves it’s more than a “pie in the sky” concept. It has real production possibilities; and we’re delighted that Porsche sees driving fun as a vital part of its future.

Sumber: yahoo News

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Chile Earthquacke changed the entire Earth's rotation and shortened the length of days on our planet.

2010-03-02T11:37:00.000-08:00

The massive 8.8 earthquake that struck Chile may have changed the entire Earth's rotation and shortened the length of days on our planet, a NASA scientist said Monday.

The quake, the seventh strongest earthquake in recorded history, hit Chile Saturday and should have shortened the length of an Earth day by 1.26 milliseconds, according to research scientist Richard Gross at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

"Perhaps more impressive is how much the quake shifted Earth's axis," NASA officials said in a Monday update.

The computer model used by Gross and his colleagues to determine the effects of the Chile earthquake effect also found that it should have moved Earth's figure axis by about 3 inches (8 cm or 27 milliarcseconds).

The Earth's figure axis is not the same as its north-south axis, which it spins around once every day at a speed of about 1,000 mph (1,604 kph).

The figure axis is the axis around which the Earth's mass is balanced. It is offset from the Earth's north-south axis by about 33 feet (10 meters).

Strong earthquakes have altered Earth's days and its axis in the past. The 9.1 Sumatran earthquake in 2004, which set off a deadly tsunami, should have shortened Earth's days by 6.8 microseconds and shifted its axis by about 2.76 inches (7 cm, or 2.32 milliarcseconds).

One Earth day is about 24 hours long. Over the course of a year, the length of a day normally changes gradually by one millisecond. It increases in the winter, when the Earth rotates more slowly, and decreases in the summer, Gross has said in the past.

The Chile earthquake was much smaller than the Sumatran temblor, but its effects on the Earth are larger because of its location. Its epicenter was located in the Earth's mid-latitudes rather than near the equator like the Sumatran event.

The fault responsible for the 2010 Chile quake also slices through Earth at a steeper angle than the Sumatran quake's fault, NASA scientists said.

"This makes the Chile fault more effective in moving Earth's mass vertically and hence more effective in shifting Earth's figure axis," NASA officials said.

Gross said his findings are based on early data available on the Chile earthquake. As more information about its characteristics are revealed, his prediction of its effects will likely change.

The Chile earthquake has killed more than 700 people and caused widespread devastation in the South American country.

Several major telescopes in Chile's Atacama Desert have escaped damage, according to the European Southern Observatory managing them.

A salt-measuring NASA satellite instrument destined to be installed on an Argentinean satellite was also undamaged in the earthquake, JPL officials said.

The Aquarius instrument was in the city of Bariloche, Argentina, where it is being installed in the Satelite de Aplicaciones Cientificas (SAC-D) satellite. The satellite integration facility is about 365 miles (588 km) from the Chile quake's epicenter.

The Aquarius instrument is designed to provide monthly global maps of the ocean's salt concentration in order to track current circulation and its role in climate change.

Source: yahoo news

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Google acquires photo-editing site??

2010-03-02T04:09:00.000-08:00

SAN FRANCISCO (Reuters) – Google Inc acquired online photo-editing site Picnik, as the Web search leader continues with a deal binge includes three acquisitions in about three weeks.

Google did not disclose the financial terms of the deal for Picnik, a 5-year-old Seattle-based start-up which said on its website that it has 20 employees.

Google spokesman Andrew Pederson said in an email message that the Picnik team has joined Google's Seattle office and will work with Google's Picasa group. Picasa is Google's Web photo sharing service.

The deal is the latest example of Google's increasing appetite for acquisitions, as the company's core Internet search business has benefited from a recovery in the advertising sector.

In October, Google CEO Eric Schmidt said the company would resume its historic pace of acquiring one small company per month on average, with larger deals happening every year or two.

Last month Google acquired Aardvark, a social search engine andmobile Web email service reMail. Since September, Google has acquired 8 companies, said Pederson.

Google Chief Financial Officer Patrick Pichette, speaking at theMorgan Stanley Technology, Media and Telecom Conference on Monday, said that Google was beefing up its ranks as business conditions improve.

"The bottleneck for us right now is engineering. How many engineers can we find given that we have all these great opportunities?" Pichette said.

Picnik allows users to edit online photos from directly within a Web browser, eliminating the need for special, stand-alone editing software.

Sumber: Yahoo

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General Motors Co is recalling 1.3 million Cars

2010-03-02T02:28:00.000-08:00

DETROIT (Reuters) – General Motors Co is recalling 1.3 million compact cars in North America to address a power steering problem that has been linked to 14 crashes and one injury, the company said on Tuesday.
U.S. safety regulators opened an investigation on January 27 into approximately 905,000 Cobalt models in the United States after receiving more than 1,100 complaints of power steering failures. The complaints included 14 crashes and one injury.
The recall covers the 2005-2010 model year Chevrolet Cobalt and 2007-2010 Pontiac G5 in the United States; 2005-2006 Pontiac Pursuit sold in Canada, and the 2005-2006 Pontiac G4 sold in Mexico, GM said in a statement.
GM said it told the U.S. National Highway Traffic Safety Administration about the voluntary recall on Monday after concluding its own investigation that began in 2009.
GM said the affected vehicles can be still be "safely controlled" but it may require greater steering effort under 15 mph. Drivers will see a warning light and hear a chime if the power steering fails.
"After our in-depth investigation, we found that this is a condition that takes time to develop. It tends to occur in older models out of warranty," GM Vice President of Quality Jamie Hresko said in the statement.
"Recalling these vehicles is the right thing to do for our customers' peace of mind," he said.
GM said it is currently developing a remedy to fix the problem and will notify customers when the plan is finalized.
The recall comes at a time of heighted public and regulatory scrutiny over vehicle safety issues in the wake of massive recalls by Toyota Motor Corp.
Toyota global quality control chief Shinichi Sasaki and North American President Yoshimi Inaba are scheduled to appear before a Senate committee on Tuesday for a third hearing on its handling of consumer complaints about sudden acceleration.

Source: yahoo news

Playstation 3 FAT trouble

2010-03-02T02:21:00.000-08:00

For the last day or so, many users around the globe have reported problems with their PlayStation 3 gaming consoles, particularly when trying to get online with them. Error codes, lack of PlayStation Network service, and disappearing trophies are some of the symptoms plaguing gamers.
Sony has now released a statement saying they've found the problem and are working on a fix. For gamers who have the PS3 Slim model, released last fall, you're okay to keep on playing, same as before, and can relax. For those who have the original larger-formfactor console, Sony advises you to not use your console for the next 24 hours while they complete the fix.
Data loss and the lack of the ability to record obtained Trophies are both listed as possible problems with using it during the next day. The full statement from Sony, run on the PlayStation Blog, is reprinted below:
As you may be aware, some customers have been unable to connect to the PlayStation Network today. This problem affects all models other than the new slim PS3.
We believe we have identified that this problem is being caused by a bug in the clock functionality incorporated in the system.
Errors include:

The date of the PS3 system may be re-set to Jan 1, 2000.
When the user tries to sign in to the PlayStation Network, the following
message appears on the screen; "An error has occurred. You have been
signed out of PlayStation Network (8001050F)".
When the user tries to launch a game, the following error message appears
on the screen and the trophy data may disappear; "Failed to install
trophies. Please exit your game."
When the user tries to set the time and date of the system via the
Internet, the following message appears on the screen; "The current date
and time could not be obtained. (8001050F)"
Users are not able to play back certain rental video downloaded from the
PlayStation Store before the expiration date.

We hope to resolve this problem within the next 24 hours. In the meantime, if you have a model other than the new slim PS3, we advise that you do not use your PS3 system, as doing so may result in errors in some functionality, such as recording obtained trophies, and not being able to restore certain data.
As mentioned above, please be advised that the new slim PS3 is not affected with this error. We are doing our best to resolve the issue and do apologize for any inconvenience caused.
For the latest status on this situation please continue to check either the PlayStation.Blog or PlayStation.com.

Source: Yahoonews

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AMD Virtualization Techology

2008-12-31T12:02:00.000-08:00

What is AMD Virtualization™ technology?

AMD Virtualization (AMD-V™) technology allows you to better utilize your resources, which makes your servers, workstations, and datacenters more effective.

Today’s servers typically operate at less than 15 percent capacity, yet still consume power and generate heat on a 24x7 basis. Virtualization technology not only addresses server underutilization, but also provides additional benefits such as improved manageability and a reduction of power and cooling costs.

AMD Opteron™ processors provide a solid foundation for the evolution to x64-based virtualization, giving companies the ability to run both 32- and 64-bit virtual machines on the same server.

The combined effects of Direct Connect Architecture, an integrated memory controller, HyperTransport™ technology, and AMD-V technology with Rapid Virtualization Indexing help to streamline your datacenter and maximize your IT investment - reduce power consumption, support more users, more transactions, and more resource-intensive applications and achieve higher levels of efficiency and utilization in your virtual environment.

How does AMD Virtualization technology work?

AMD-V™ technology is a set of hardware extensions to the x86 system architecture, designed to improve the efficiency and reduce the performance overhead of software based virtualization solutions. AMD-V simplifies existing software only virtualization solutions by reducing and sometimes eliminating the burden of trapping and emulating instructions executed within a guest operating system. In addition, AMD-V™ technology leverages the AMD Opteron processor with Direct Connect Architecture to provide fast and efficient memory handling, which is a must-have for memory intensive applications like virtualization.

Why AMD Opteron™ processors and AMD Virtualization technology?

Virtualization is a memory and compute intensive environment, putting demands on servers not found in many other software environments. You need a server platform that can provide a robust and scalable environment for virtualization while maintaining power efficiency. With Direct Connect Architecture, system bottlenecks inherent in front side bus architectures are reduced. HyperTransport™ technology enables high-speed I/O for better sharing of resources. AMD’s Integrated Memory Controller can offer crucial low-latency, high-bandwidth memory access needed to fuel the memory hungry virtualization environment. AMD-V technology with Rapid Virtualization Indexing helps improve performance of virtualized applications and reduces software virtualization overhead. No other processor vendor can match AMD’s capabilities for x86 virtualization:
Unmatched Memory Bandwidth and Scalability - Direct Connect Architecture allows more virtual machines (VMs) to be hosted per server and more users and transactions per virtual machines

Enhanced Power Management - Intelligently manages power consumption so that you don’t waste energy during low utilization cycles

Rapid Virtualization Indexing - Helps accelerate the performance of many virtualized applications by enabling hardware-based VM memory management. Rapid Virtualization Indexing (RVI) allows virtual machines to directly manage memory utilizing hardware resources rather than software resources. RVI can help reduce Hypervisor cycles and the associated performance penalty that is commonly associated with virtualization.

For an in depth look at AMD-V and Rapid Virtualization Indexing technology click here

Tagged TLB - Hardware features that facilitate efficient switching between VMs for better application responsiveness

AMD-V Extended Migration - Hardware feature that helps virtualization software enable live migration of virtual machines between all available AMD Opteron™ processor generations.

source : amd.com

AMD Opteron

2008-12-31T11:56:00.000-08:00

AMD announces the widespread availability of its 45nm Quad-Core AMD Opteron processor, which delivers up to 35 percent more performance with up to a 35 percent decrease in power consumption at idle. With IT decision-makers looking to do more with less, the newest Quad-Core AMD Opteron processor can help drive data center efficiencies and reduce complexities with innovations that offer superior virtualization performance and increased performance-per-watt. Global OEMs are expected to immediately offer enterprise and SMB customers more than 27 systems, available between launch today and the end of the year, based on the 45nm Quad-Core AMD Opteron processor, formerly code-named "Shanghai."

-Optimal Virtualization-

Quad-Core AMD Opteron™ processors are designed to accelerate the performance of virtualized applications and improve system utilization with enhanced AMD Virtualization™ (AMD-V™) technology.

- Power Efficiency -

AMD helps lower energy consumption and cooling costs of data centers with unique power management technology and ground-breaking performance-per-watt of Quad-Core AMD Opteron™ processors.

- Powering The Web -

AMD Opteron™ processors boast superior ability to handle the strenuous and mounting demands placed on today’s high-traffic Web-based businesses, delivering high scalability designed to handle heavy user traffic while balancing cost and power concerns.

- Outstanding Performance -

The AMD Opteron™ processor was designed to remove on-chip inefficiencies, helping to maximize performance with minimal expense. Trusted in cutting edge data centers and high performance computing architecture, AMD is relied upon to help provide superior performance boost for the working environments of today and tomorrow.

source : http://www.amd.com/us-en/0,,3715_15251,00.html

Way Back Into The Love

2008-12-22T01:07:00.000-08:00

I've been living with a shadow overhead
I've been sleeping with a cloud above my bed
I've been lonely for so long
Trapped in the past
I just can't seem to move on

I've been hiding all my hopes and dreams away
Just in case I ever need them again someday
I've been setting aside time
To clear a little space in the corners of my mind

All I want to do is find a way back into love
I can't make it through without a way back into love
Oh oh oh

I've been watching but the stars refuse to shine
I've been searching but i just don't see the signs
I know that it's out there
There's got to be something for my soul somewhere

I've been looking for someone to shed some light
Not somebody just to get me through the night
I could use some direction
And I'm open to your suggestions

All I want to do is find a way back into love
I can't make it through without a way back into love
And if I open my heart again
I guess I'm hoping you'll be there for me in the end

Oh oh oh

There are moments when I don't know if it's real
Or if anybody feels the way I feel
I need inspiration
Not just another negotiation

All I want to do is find a way back into love
I can't make it through without a way back into love
And if I open my heart to you
I'm hoping you'll show me what to do
And if you help me to start again
You know that I'll be there for you in the end

Oh oh oh

source : http://www.stlyrics.com/lyrics/music&lyrics/waybackintolove.htm

IPv6

2008-12-18T20:13:00.000-08:00

Original Article at :http://www.cisco.com/en/US/docs/internetworking/technology/handbook/IPv6.html

IPv6

One of the newest major standards on the horizon is IPv6. Although IPv6 has not officially become a standard, it is worth some overview. It is very possible that this information will change as we move closer to IPv6 as a standard, so you should use this as a guide into IPv6, not the definitive information.

A number of books are now being published that cover in detail this emerging standard; if you are looking for more details you should refer to these books. All the RFCs available on the Internet have the raw details on how this standard is developing. However, these documents are difficult to interpret at first glance and require some commitment to going through any number of RFCs pertaining to many subjects all related to IPv6 development.

Internet Protocol Version 4 is the most popular protocol in use today (see Chapter 31, "Internet Protocols"), although there are some questions about its capability to serve the Internet community much longer. IPv4 was finished in the 1970s and has started to show its age. The main issue surrounding IPv6 is addressing—or, the lack of addressing—because many experts believe that we are nearly out of the four billion addresses available in IPv4. Although this seems like a very large number of addresses, multiple large blocks are given to government agencies and large organizations. IPv6 could be the solution to many problems, but it is still not fully developed and is not a standard—yet!

Many of the finest developers and engineering minds have been working on IPv6 since the early 1990s. Hundreds of RFCs have been written and have detailed some major areas, including expanded addressing, simplified header format, flow labeling, authentication, and privacy.

Expanded addressing moves us from 32-bit address to a 128-bit addressing method. It also provides newer unicast and broadcasting methods, injects hexadecimal into the IP address, and moves from using "." to using ":" as delimiters. Figure 32-1 shows the IPv6 packet header format.

Figure 32-1 IPv6 Packet Header Format

Description of IPv6 Packet Header

The simplified header is 40 bits long and the format consists of Version, Class, Flow Label, Payload Length, Next Header, Hop Limit, Source Address, Destination Address, Data, and Payload fields.
Hexadecimal "Hex"

At its simplest, hex numbers are base 16. Decimal is base 10, counting from 0 to 9, as we do in decimal, and then adding a column to make 10. Counting in hex goes from 0 to F before adding a column. The characters A through F represent the decimal values of 10 through 15, as illustrated in Figure 32-2.

Figure 32-2 Hex Characters A Through F Represent the Numbers 10 Through 15

Counting in hex goes as follows: 0 1 2 3 4 5 6 7 8 9 A B C D E F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F 20 21 and up, as far as you want to go.
Addressing Description

Let's look at an example of IPv6 address. The address is an eight-part hex address separated by colons (" :"). Each part n can equal a 16-bit number and is eight parts long, providing a 128-bit address length (16 ¥ 8 = 128),

Addresses are n:n:n:n:n:n:n:n n = 4 digit hexadecimal integer, 16 ¥ 8 = 128 address.

1080:0:0:0:8:800:200C:417A Unicast address

FF01:0:0:0:0:0:0:101 Multicast address
Broadcasting Methods

Included in IPv6 are a number of new broadcasting methods:

•Unicast

•Multicast

•Anycast
Unicast

Unicast is a communication between a single host and a single receiver. Packets sent to
a unicast address are delivered to the interface identified by that address, as seen in
Figure 32-3.

Figure 32-3 Unicast Sends Packets to a Specified Interface

Multicast

Multicast is communication between a single host and multiple receivers. Packets are sent to all interfaces identified by that address, as seen in Figure 32-4.

Figure 32-4 Multicast Sends Packets to a Subnet, and Defined Devices Listen for Multicast Packets

Anycast

Packets sent to an anycast address or list of addresses are delivered to the nearest interface identified by that address. Anycast is a communication between a single sender and a list of addresses, as shown in Figure 32-5.

Figure 32-5 Anycast Sends Packets to Specified Interface List and Can Contain End Nodes and Routers

Summary

Some of the benefits of IPv6 seem obvious: greater addressing space, built-in QoS, and better routing performance and services. However, a number of barriers must be overcome before the implementation of IPv6. The biggest question for most of us will be what the business need is for moving from current IPv4 to IPv6. The killer app has not appeared yet, but it may be closer than we think. The second consideration is the cost—it may not have much to do with hardware replacement cost. All the larger routers have upgradable OSs IOS; the only necessity is the commitment to upgrading IOS. More likely to do with training and support of minor IP devices such as printers and network faxes, they will support the new address space. IPv6 has schemes to support old and new, however, so this may not even be a barrier. The last issue to consider is training: This will need to happen sooner or later because we all need to start thinking about 128-bit addressing based on MAC addresses in HEX. This involves all new ways of addressing and will be an uncomfortable change for many people.

This conclusion may seem negative, but the greater good will overpower all the up-front issues. The issue is not whether you will have to move to IPv6, but when! We all need IPv6; the increased address space is needed for the growth of IP appliances that we are starting to hear about weekly. IP-ready cars are already shipping today. This requires mobility, which is addressed in IPv6.

Of course, a number of very important features have not been discussed in this section, including QoS, mobile IP, autoconfiguration, and security. All these areas are extremely important, and until IPv6 is finished, you should keep referring to the IETF Web site for the most current information. Several new books on IPv6 also are starting to show up on bookstore shelves and should provide the deeper technical detail on address headers and full packet details.

download article here

Internetworking Basics

2008-12-18T20:06:00.000-08:00

Original Article at :http://www.cisco.com/en/US/docs/internetworking/technology/handbook/Intro-to-Internet.html

Internetworking Basics

This chapter works with the next six chapters to act as a foundation for the technology discussions that follow. In this chapter, some fundamental concepts and terms used in the evolving language of internetworking are addressed. In the same way that this book provides a foundation for understanding modern networking, this chapter summarizes some common themes presented throughout the remainder of this book. Topics include flow control, error checking, and multiplexing, but this chapter focuses mainly on mapping the Open System Interconnection (OSI) model to networking/internetworking functions, and also summarizing the general nature of addressing schemes within the context
of the OSI model. The OSI model represents the building blocks for internetworks. Understanding the conceptual model helps you understand the complex pieces that make up an internetwork.
What Is an Internetwork?

An internetwork is a collection of individual networks, connected by intermediate networking devices, that functions as a single large network. Internetworking refers to the industry, products, and procedures that meet the challenge of creating and administering internetworks. Figure 1-1 illustrates some different kinds of network technologies that can be interconnected by routers and other networking devices to create an internetwork.

Figure 1-1 Different Network Technologies Can Be Connected to Create an Internetwork

History of Internetworking

The first networks were time-sharing networks that used mainframes and attached terminals. Such environments were implemented by both IBM's Systems Network Architecture (SNA) and Digital's network architecture.

Local-area networks (LANs) evolved around the PC revolution. LANs enabled multiple users in a relatively small geographical area to exchange files and messages, as well as access shared resources such as file servers and printers.

Wide-area networks (WANs) interconnect LANs with geographically dispersed users to create connectivity. Some of the technologies used for connecting LANs include T1, T3, ATM, ISDN, ADSL, Frame Relay, radio links, and others. New methods of connecting dispersed LANs are appearing everyday.

Today, high-speed LANs and switched internetworks are becoming widely used, largely because they operate at very high speeds and support such high-bandwidth applications as multimedia and videoconferencing.

Internetworking evolved as a solution to three key problems: isolated LANs, duplication
of resources, and a lack of network management. Isolated LANs made electronic communication between different offices or departments impossible. Duplication of resources meant that the same hardware and software had to be supplied to each office or department, as did separate support staff. This lack of network management meant that no centralized method of managing and troubleshooting networks existed.
Internetworking Challenges

Implementing a functional internetwork is no simple task. Many challenges must be faced, especially in the areas of connectivity, reliability, network management, and flexibility. Each area is key in establishing an efficient and effective internetwork.

The challenge when connecting various systems is to support communication among disparate technologies. Different sites, for example, may use different types of media operating at varying speeds, or may even include different types of systems that need to communicate.

Because companies rely heavily on data communication, internetworks must provide a certain level of reliability. This is an unpredictable world, so many large internetworks include redundancy to allow for communication even when problems occur.

Furthermore, network management must provide centralized support and troubleshooting capabilities in an internetwork. Configuration, security, performance, and other issues must be adequately addressed for the internetwork to function smoothly. Security within an internetwork is essential. Many people think of network security from the perspective of protecting the private network from outside attacks. However, it is just as important to protect the network from internal attacks, especially because most security breaches come from inside. Networks must also be secured so that the internal network cannot be used as a tool to attack other external sites.

Early in the year 2000, many major web sites were the victims of distributed denial of service (DDOS) attacks. These attacks were possible because a great number of private networks currently connected with the Internet were not properly secured. These private networks were used as tools for the attackers.

Because nothing in this world is stagnant, internetworks must be flexible enough to change with new demands.
Open System Interconnection Reference Model

The Open System Interconnection (OSI) reference model describes how information from a software application in one computer moves through a network medium to a software application in another computer. The OSI reference model is a conceptual model composed of seven layers, each specifying particular network functions. The model was developed by the International Organization for Standardization (ISO) in 1984, and it is now considered the primary architectural model for intercomputer communications. The OSI model divides the tasks involved with moving information between networked computers into seven smaller, more manageable task groups. A task or group of tasks is then assigned to each of the seven OSI layers. Each layer is reasonably self-contained so that the tasks assigned to each layer can be implemented independently. This enables the solutions offered by one layer to be updated without adversely affecting the other layers. The following list details the seven layers of the Open System Interconnection (OSI) reference model:

•Layer 7—Application

•Layer 6—Presentation

•Layer 5—Session

•Layer 4—Transport

•Layer 3—Network

•Layer 2—Data link

•Layer 1—Physical

Note A handy way to remember the seven layers is the sentence "All people seem to need data processing." The beginning letter of each word corresponds to a layer.

•All—Application layer

•People—Presentation layer

•Seem—Session layer

•To—Transport layer

•Need—Network layer

•Data—Data link layer

•Processing—Physical layer

Figure 1-2 illustrates the seven-layer OSI reference model.

Figure 1-2 The OSI Reference Model Contains Seven Independent Layers

Characteristics of the OSI Layers

The seven layers of the OSI reference model can be divided into two categories: upper layers and lower layers.

The upper layers of the OSI model deal with application issues and generally are implemented only in software. The highest layer, the application layer, is closest to the end user. Both users and application layer processes interact with software applications that contain a communications component. The term upper layer is sometimes used to refer to any layer above another layer in the OSI model.

The lower layers of the OSI model handle data transport issues. The physical layer and the data link layer are implemented in hardware and software. The lowest layer, the physical layer, is closest to the physical network medium (the network cabling, for example) and is responsible for actually placing information on the medium.

Figure 1-3 illustrates the division between the upper and lower OSI layers.

Figure 1-3 Two Sets of Layers Make Up the OSI Layers

Protocols

The OSI model provides a conceptual framework for communication between computers, but the model itself is not a method of communication. Actual communication is made possible by using communication protocols. In the context of data networking, a protocol is a formal set of rules and conventions that governs how computers exchange information over a network medium. A protocol implements the functions of one or more of the OSI layers.

A wide variety of communication protocols exist. Some of these protocols include LAN protocols, WAN protocols, network protocols, and routing protocols. LAN protocols operate at the physical and data link layers of the OSI model and define communication over the various LAN media. WAN protocols operate at the lowest three layers of the OSI model and define communication over the various wide-area media. Routing protocols are network layer protocols that are responsible for exchanging information between routers so that the routers can select the proper path for network traffic. Finally, network protocols are the various upper-layer protocols that exist in a given protocol suite. Many protocols rely on others for operation. For example, many routing protocols use network protocols to exchange information between routers. This concept of building upon the layers already in existence is the foundation of the OSI model.
OSI Model and Communication Between Systems

Information being transferred from a software application in one computer system to a software application in another must pass through the OSI layers. For example, if a software application in System A has information to transmit to a software application in System B, the application program in System A will pass its information to the application layer (Layer 7) of System A. The application layer then passes the information to the presentation layer (Layer 6), which relays the data to the session layer (Layer 5), and so on down to the physical layer (Layer 1). At the physical layer, the information is placed on the physical network medium and is sent across the medium to System B. The physical layer of System B removes the information from the physical medium, and then its physical layer passes the information up to the data link layer (Layer 2), which passes it to the network layer (Layer 3), and so on, until it reaches the application layer (Layer 7) of System B. Finally, the application layer of System B passes the information to the recipient application program to complete the communication process.
Interaction Between OSI Model Layers

A given layer in the OSI model generally communicates with three other OSI layers: the layer directly above it, the layer directly below it, and its peer layer in other networked computer systems. The data link layer in System A, for example, communicates with the network layer of System A, the physical layer of System A, and the data link layer in System B. Figure 1-4 illustrates this example.

Figure 1-4 OSI Model Layers Communicate with Other Layers

OSI Layer Services

One OSI layer communicates with another layer to make use of the services provided by the second layer. The services provided by adjacent layers help a given OSI layer communicate with its peer layer in other computer systems. Three basic elements are involved in layer services: the service user, the service provider, and the service access point (SAP).

In this context, the service user is the OSI layer that requests services from an adjacent OSI layer. The service provider is the OSI layer that provides services to service users. OSI layers can provide services to multiple service users. The SAP is a conceptual location at which one OSI layer can request the services of another OSI layer.

Figure 1-5 illustrates how these three elements interact at the network and data link layers.

Figure 1-5 Service Users, Providers, and SAPs Interact at the Network and Data Link Layers

OSI Model Layers and Information Exchange

The seven OSI layers use various forms of control information to communicate with their peer layers in other computer systems. This control information consists of specific requests and instructions that are exchanged between peer OSI layers.

Control information typically takes one of two forms: headers and trailers. Headers are prepended to data that has been passed down from upper layers. Trailers are appended to data that has been passed down from upper layers. An OSI layer is not required to attach a header or a trailer to data from upper layers.

Headers, trailers, and data are relative concepts, depending on the layer that analyzes the information unit. At the network layer, for example, an information unit consists of a Layer 3 header and data. At the data link layer, however, all the information passed down by the network layer (the Layer 3 header and the data) is treated as data.

In other words, the data portion of an information unit at a given OSI layer potentially
can contain headers, trailers, and data from all the higher layers. This is known as encapsulation. Figure 1-6 shows how the header and data from one layer are encapsulated into the header of the next lowest layer.

Figure 1-6 Headers and Data Can Be Encapsulated During Information Exchange

Information Exchange Process

The information exchange process occurs between peer OSI layers. Each layer in the source system adds control information to data, and each layer in the destination system analyzes and removes the control information from that data.

If System A has data from a software application to send to System B, the data is passed to the application layer. The application layer in System A then communicates any control information required by the application layer in System B by prepending a header to the data. The resulting information unit (a header and the data) is passed to the presentation layer, which prepends its own header containing control information intended for the presentation layer in System B. The information unit grows in size as each layer prepends its own header (and, in some cases, a trailer) that contains control information to be used by its peer layer in System B. At the physical layer, the entire information unit is placed onto the network medium.

The physical layer in System B receives the information unit and passes it to the data link layer. The data link layer in System B then reads the control information contained in the header prepended by the data link layer in System A. The header is then removed, and the remainder of the information unit is passed to the network layer. Each layer performs the same actions: The layer reads the header from its peer layer, strips it off, and passes the remaining information unit to the next highest layer. After the application layer performs these actions, the data is passed to the recipient software application in System B, in exactly the form in which it was transmitted by the application in System A.
OSI Model Physical Layer

The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between communicating network systems. Physical layer specifications define characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and physical connectors. Physical layer implementations can be categorized as either LAN or WAN specifications. Figure 1-7 illustrates some common LAN and WAN physical layer implementations.

Figure 1-7 Physical Layer Implementations Can Be LAN or WAN Specifications

OSI Model Data Link Layer

The data link layer provides reliable transit of data across a physical network link. Different data link layer specifications define different network and protocol characteristics, including physical addressing, network topology, error notification, sequencing of frames, and flow control. Physical addressing (as opposed to network addressing) defines how devices are addressed at the data link layer. Network topology consists of the data link layer specifications that often define how devices are to be physically connected, such as in a bus or a ring topology. Error notification alerts upper-layer protocols that a transmission error has occurred, and the sequencing of data frames reorders frames that are transmitted out of sequence. Finally, flow control moderates the transmission of data so that the receiving device is not overwhelmed with more traffic than it can handle at one time.

The Institute of Electrical and Electronics Engineers (IEEE) has subdivided the data link layer into two sublayers: Logical Link Control (LLC) and Media Access Control (MAC). Figure 1-8 illustrates the IEEE sublayers of the data link layer.

Figure 1-8 The Data Link Layer Contains Two Sublayers

The Logical Link Control (LLC) sublayer of the data link layer manages communications between devices over a single link of a network. LLC is defined in the IEEE 802.2 specification and supports both connectionless and connection-oriented services used by higher-layer protocols. IEEE 802.2 defines a number of fields in data link layer frames that enable multiple higher-layer protocols to share a single physical data link. The Media Access Control (MAC) sublayer of the data link layer manages protocol access to the physical network medium. The IEEE MAC specification defines MAC addresses, which enable multiple devices to uniquely identify one another at the data link layer.
OSI Model Network Layer

The network layer defines the network address, which differs from the MAC address. Some network layer implementations, such as the Internet Protocol (IP), define network addresses in a way that route selection can be determined systematically by comparing the source network address with the destination network address and applying the subnet mask. Because this layer defines the logical network layout, routers can use this layer to determine how to forward packets. Because of this, much of the design and configuration work for internetworks happens at Layer 3, the network layer.
OSI Model Transport Layer

The transport layer accepts data from the session layer and segments the data for transport across the network. Generally, the transport layer is responsible for making sure that the data is delivered error-free and in the proper sequence. Flow control generally occurs at the transport layer.

Flow control manages data transmission between devices so that the transmitting device does not send more data than the receiving device can process. Multiplexing enables data from several applications to be transmitted onto a single physical link. Virtual circuits are established, maintained, and terminated by the transport layer. Error checking involves creating various mechanisms for detecting transmission errors, while error recovery involves acting, such as requesting that data be retransmitted, to resolve any errors that occur.

The transport protocols used on the Internet are TCP and UDP.
OSI Model Session Layer

The session layer establishes, manages, and terminates communication sessions. Communication sessions consist of service requests and service responses that occur between applications located in different network devices. These requests and responses are coordinated by protocols implemented at the session layer. Some examples of session-layer implementations include Zone Information Protocol (ZIP), the AppleTalk protocol that coordinates the name binding process; and Session Control Protocol (SCP), the DECnet Phase IV session layer protocol.
OSI Model Presentation Layer

The presentation layer provides a variety of coding and conversion functions that are applied to application layer data. These functions ensure that information sent from the application layer of one system would be readable by the application layer of another system. Some examples of presentation layer coding and conversion schemes include common data representation formats, conversion of character representation formats, common data compression schemes, and common data encryption schemes.

Common data representation formats, or the use of standard image, sound, and video formats, enable the interchange of application data between different types of computer systems. Conversion schemes are used to exchange information with systems by using different text and data representations, such as EBCDIC and ASCII. Standard data compression schemes enable data that is compressed at the source device to be properly decompressed at the destination. Standard data encryption schemes enable data encrypted at the source device to be properly deciphered at the destination.

Presentation layer implementations are not typically associated with a particular protocol stack. Some well-known standards for video include QuickTime and Motion Picture Experts Group (MPEG). QuickTime is an Apple Computer specification for video and audio, and MPEG is a standard for video compression and coding.

Among the well-known graphic image formats are Graphics Interchange Format (GIF), Joint Photographic Experts Group (JPEG), and Tagged Image File Format (TIFF). GIF is a standard for compressing and coding graphic images. JPEG is another compression and coding standard for graphic images, and TIFF is a standard coding format for graphic images.
OSI Model Application Layer

The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and the user interact directly with the software application.

This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication.

When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit.
When determining resource availability, the application layer must decide whether sufficient network resources for the requested communication exist. In synchronizing communication, all communication between applications requires cooperation that is managed by the application layer.

Some examples of application layer implementations include Telnet, File Transfer Protocol (FTP), and Simple Mail Transfer Protocol (SMTP).
Information Formats

The data and control information that is transmitted through internetworks takes a variety of forms. The terms used to refer to these information formats are not used consistently
in the internetworking industry but sometimes are used interchangeably. Common information formats include frames, packets, datagrams, segments, messages, cells, and data units.

A frame is an information unit whose source and destination are data link layer entities. A frame is composed of the data link layer header (and possibly a trailer) and upper-layer data. The header and trailer contain control information intended for the data link layer entity in the destination system. Data from upper-layer entities is encapsulated in the data link layer header and trailer. Figure 1-9 illustrates the basic components of a data link layer frame.

Figure 1-9 Data from Upper-Layer Entities Makes Up the Data Link Layer Frame

A packet is an information unit whose source and destination are network layer entities. A packet is composed of the network layer header (and possibly a trailer) and upper-layer data. The header and trailer contain control information intended for the network layer entity in the destination system. Data from upper-layer entities is encapsulated in the network layer header and trailer. Figure 1-10 illustrates the basic components of a network layer packet.

Figure 1-10 Three Basic Components Make Up a Network Layer Packet

The term datagram usually refers to an information unit whose source and destination are network layer entities that use connectionless network service.

The term segment usually refers to an information unit whose source and destination are transport layer entities.

A message is an information unit whose source and destination entities exist above the network layer (often at the application layer).

A cell is an information unit of a fixed size whose source and destination are data link layer entities. Cells are used in switched environments, such as Asynchronous Transfer Mode (ATM) and Switched Multimegabit Data Service (SMDS) networks. A cell is composed
of the header and payload. The header contains control information intended for the destination data link layer entity and is typically 5 bytes long. The payload contains upper-layer data that is encapsulated in the cell header and is typically 48 bytes long.

The length of the header and the payload fields always are the same for each cell.
Figure 1-11 depicts the components of a typical cell.

Figure 1-11 Two Components Make Up a Typical Cell

Data unit is a generic term that refers to a variety of information units. Some common data units are service data units (SDUs), protocol data units, and bridge protocol data units (BPDUs). SDUs are information units from upper-layer protocols that define a service request to a lower-layer protocol. PDU is OSI terminology for a packet. BPDUs are used by the spanning-tree algorithm as hello messages.
ISO Hierarchy of Networks

Large networks typically are organized as hierarchies. A hierarchical organization provides such advantages as ease of management, flexibility, and a reduction in unnecessary traffic. Thus, the International Organization for Standardization (ISO) has adopted a number of terminology conventions for addressing network entities. Key terms defined in this section include end system (ES), intermediate system (IS), area, and autonomous system (AS).

An ES is a network device that does not perform routing or other traffic forwarding functions. Typical ESs include such devices as terminals, personal computers, and printers. An IS is a network device that performs routing or other traffic-forwarding functions. Typical ISs include such devices as routers, switches, and bridges. Two types of IS networks exist: intradomain IS and interdomain IS. An intradomain IS communicates within a single autonomous system, while an interdomain IS communicates within and between autonomous systems. An area is a logical group of network segments and their attached devices. Areas are subdivisions of autonomous systems (AS's). An AS is a collection of networks under a common administration that share a common routing strategy. Autonomous systems are subdivided into areas, and an AS is sometimes called a domain. Figure 1-12 illustrates a hierarchical network and its components.

Figure 1-12 A Hierarchical Network Contains Numerous Components

Connection-Oriented and Connectionless Network Services

In general, transport protocols can be characterized as being either connection-oriented or connectionless. Connection-oriented services must first establish a connection with the desired service before passing any data. A connectionless service can send the data without any need to establish a connection first. In general, connection-oriented services provide some level of delivery guarantee, whereas connectionless services do not.

Connection-oriented service involves three phases: connection establishment, data transfer, and connection termination.

During connection establishment, the end nodes may reserve resources for the connection. The end nodes also may negotiate and establish certain criteria for the transfer, such as a window size used in TCP connections. This resource reservation is one of the things exploited in some denial of service (DOS) attacks. An attacking system will send many requests for establishing a connection but then will never complete the connection. The attacked computer is then left with resources allocated for many never-completed connections. Then, when an end node tries to complete an actual connection, there are not enough resources for the valid connection.

The data transfer phase occurs when the actual data is transmitted over the connection. During data transfer, most connection-oriented services will monitor for lost packets and handle resending them. The protocol is generally also responsible for putting the packets in the right sequence before passing the data up the protocol stack.

When the transfer of data is complete, the end nodes terminate the connection and release resources reserved for the connection.

Connection-oriented network services have more overhead than connectionless ones. Connection-oriented services must negotiate a connection, transfer data, and tear down the connection, whereas a connectionless transfer can simply send the data without the added overhead of creating and tearing down a connection. Each has its place in internetworks.
Internetwork Addressing

Internetwork addresses identify devices separately or as members of a group. Addressing schemes vary depending on the protocol family and the OSI layer. Three types of internetwork addresses are commonly used: data link layer addresses, Media Access Control (MAC) addresses, and network layer addresses.
Data Link Layer Addresses

A data link layer address uniquely identifies each physical network connection of a network device. Data-link addresses sometimes are referred to as physical or hardware addresses. Data-link addresses usually exist within a flat address space and have a pre-established and typically fixed relationship to a specific device.

End systems generally have only one physical network connection and thus have only one data-link address. Routers and other internetworking devices typically have multiple physical network connections and therefore have multiple data-link addresses. Figure 1-13 illustrates how each interface on a device is uniquely identified by a data-link address.

Figure 1-13 Each Interface on a Device Is Uniquely Identified by a Data-Link Address.

MAC Addresses

Media Access Control (MAC) addresses consist of a subset of data link layer addresses. MAC addresses identify network entities in LANs that implement the IEEE MAC addresses of the data link layer. As with most data-link addresses, MAC addresses are unique for each LAN interface. Figure 1-14 illustrates the relationship between MAC addresses, data-link addresses, and the IEEE sublayers of the data link layer.

Figure 1-14 MAC Addresses, Data-Link Addresses, and the IEEE Sublayers of the Data Link Layer Are All Related

MAC addresses are 48 bits in length and are expressed as 12 hexadecimal digits. The first 6 hexadecimal digits, which are administered by the IEEE, identify the manufacturer or vendor and thus comprise the Organizationally Unique Identifier (OUI). The last 6 hexadecimal digits comprise the interface serial number, or another value administered by the specific vendor. MAC addresses sometimes are called burned-in addresses (BIAs) because they are burned into read-only memory (ROM) and are copied into random-access memory (RAM) when the interface card initializes. Figure 1-15 illustrates the MAC address format.

Figure 1-15 The MAC Address Contains a Unique Format of Hexadecimal Digits

Mapping Addresses

Because internetworks generally use network addresses to route traffic around the network, there is a need to map network addresses to MAC addresses. When the network layer has determined the destination station's network address, it must forward the information over a physical network using a MAC address. Different protocol suites use different methods to perform this mapping, but the most popular is Address Resolution Protocol (ARP).

Different protocol suites use different methods for determining the MAC address of a device. The following three methods are used most often. Address Resolution Protocol (ARP) maps network addresses to MAC addresses. The Hello protocol enables network devices to learn the MAC addresses of other network devices. MAC addresses either are embedded in the network layer address or are generated by an algorithm.

Address Resolution Protocol (ARP) is the method used in the TCP/IP suite. When a network device needs to send data to another device on the same network, it knows the source and destination network addresses for the data transfer. It must somehow map the destination address to a MAC address before forwarding the data. First, the sending station will check its ARP table to see if it has already discovered this destination station's MAC address. If it has not, it will send a broadcast on the network with the destination station's IP address contained in the broadcast. Every station on the network receives the broadcast and compares the embedded IP address to its own. Only the station with the matching IP address replies to the sending station with a packet containing the MAC address for the station. The first station then adds this information to its ARP table for future reference and proceeds to transfer the data.

When the destination device lies on a remote network, one beyond a router, the process is the same except that the sending station sends the ARP request for the MAC address of its default gateway. It then forwards the information to that device. The default gateway will then forward the information over whatever networks necessary to deliver the packet to the network on which the destination device resides. The router on the destination device's network then uses ARP to obtain the MAC of the actual destination device and delivers the packet.

The Hello protocol is a network layer protocol that enables network devices to identify one another and indicate that they are still functional. When a new end system powers up, for example, it broadcasts hello messages onto the network. Devices on the network then return hello replies, and hello messages are also sent at specific intervals to indicate that they are still functional. Network devices can learn the MAC addresses of other devices by examining Hello protocol packets.

Three protocols use predictable MAC addresses. In these protocol suites, MAC addresses are predictable because the network layer either embeds the MAC address in the network layer address or uses an algorithm to determine the MAC address. The three protocols are Xerox Network Systems (XNS), Novell Internetwork Packet Exchange (IPX), and DECnet Phase IV.
Network Layer Addresses

A network layer address identifies an entity at the network layer of the OSI layers. Network addresses usually exist within a hierarchical address space and sometimes are called virtual or logical addresses.

The relationship between a network address and a device is logical and unfixed; it typically is based either on physical network characteristics (the device is on a particular network segment) or on groupings that have no physical basis (the device is part of an AppleTalk zone). End systems require one network layer address for each network layer protocol that they support. (This assumes that the device has only one physical network connection.) Routers and other internetworking devices require one network layer address per physical network connection for each network layer protocol supported. For example, a router with three interfaces each running AppleTalk, TCP/IP, and OSI must have three network layer addresses for each interface. The router therefore has nine network layer addresses. Figure 1-16 illustrates how each network interface must be assigned a network address for each protocol supported.

Figure 1-16 Each Network Interface Must Be Assigned a Network Address for Each Protocol Supported

Hierarchical Versus Flat Address Space

Internetwork address space typically takes one of two forms: hierarchical address space or flat address space. A hierarchical address space is organized into numerous subgroups, each successively narrowing an address until it points to a single device (in a manner similar to street addresses). A flat address space is organized into a single group (in a manner similar to U.S. Social Security numbers).

Hierarchical addressing offers certain advantages over flat-addressing schemes. Address sorting and recall is simplified using comparison operations. For example, "Ireland" in a street address eliminates any other country as a possible location. Figure 1-17 illustrates the difference between hierarchical and flat address spaces.

Figure 1-17 Hierarchical and Flat Address Spaces Differ in Comparison Operations

Address Assignments

Addresses are assigned to devices as one of two types: static and dynamic. Static addresses are assigned by a network administrator according to a preconceived internetwork addressing plan. A static address does not change until the network administrator manually changes it. Dynamic addresses are obtained by devices when they attach to a network, by means of some protocol-specific process. A device using a dynamic address often has a different address each time that it connects to the network. Some networks use a server to assign addresses. Server-assigned addresses are recycled for reuse as devices disconnect.
A device is therefore likely to have a different address each time that it connects to the network.
Addresses Versus Names

Internetwork devices usually have both a name and an address associated with them. Internetwork names typically are location-independent and remain associated with a device wherever that device moves (for example, from one building to another). Internetwork addresses usually are location-dependent and change when a device is moved (although MAC addresses are an exception to this rule). As with network addresses being mapped to MAC addresses, names are usually mapped to network addresses through some protocol. The Internet uses Domain Name System (DNS) to map the name of a device to its IP address. For example, it's easier for you to remember www.cisco.com instead of some IP address. Therefore, you type www.cisco.com into your browser when you want to access Cisco's web site. Your computer performs a DNS lookup of the IP address for Cisco's web server and then communicates with it using the network address.
Flow Control Basics

Flow control is a function that prevents network congestion by ensuring that transmitting devices do not overwhelm receiving devices with data. A high-speed computer, for example, may generate traffic faster than the network can transfer it, or faster than the destination device can receive and process it. The three commonly used methods for handling network congestion are buffering, transmitting source-quench messages, and windowing.

Buffering is used by network devices to temporarily store bursts of excess data in memory until they can be processed. Occasional data bursts are easily handled by buffering. Excess data bursts can exhaust memory, however, forcing the device to discard any additional datagrams that arrive.

Source-quench messages are used by receiving devices to help prevent their buffers from overflowing. The receiving device sends source-quench messages to request that the source reduce its current rate of data transmission. First, the receiving device begins discarding received data due to overflowing buffers. Second, the receiving device begins sending source-quench messages to the transmitting device at the rate of one message for each packet dropped. The source device receives the source-quench messages and lowers the data rate until it stops receiving the messages. Finally, the source device then gradually increases the data rate as long as no further source-quench requests are received.

Windowing is a flow-control scheme in which the source device requires an acknowledgment from the destination after a certain number of packets have been transmitted. With a window size of 3, the source requires an acknowledgment after sending three packets, as follows. First, the source device sends three packets to the destination device. Then, after receiving the three packets, the destination device sends an acknowledgment to the source. The source receives the acknowledgment and sends three more packets. If the destination does not receive one or more of the packets for some reason, such as overflowing buffers, it does not receive enough packets to send an acknowledgment. The source then retransmits the packets at a reduced transmission rate.
Error-Checking Basics

Error-checking schemes determine whether transmitted data has become corrupt or otherwise damaged while traveling from the source to the destination. Error checking is implemented at several of the OSI layers.

One common error-checking scheme is the cyclic redundancy check (CRC), which detects and discards corrupted data. Error-correction functions (such as data retransmission) are left to higher-layer protocols. A CRC value is generated by a calculation that is performed at the source device. The destination device compares this value to its own calculation to determine whether errors occurred during transmission. First, the source device performs a predetermined set of calculations over the contents of the packet to be sent. Then, the source places the calculated value in the packet and sends the packet to the destination. The destination performs the same predetermined set of calculations over the contents of the packet and then compares its computed value with that contained in the packet. If the values are equal, the packet is considered valid. If the values are unequal, the packet contains errors and is discarded.
Multiplexing Basics

Multiplexing is a process in which multiple data channels are combined into a single data or physical channel at the source. Multiplexing can be implemented at any of the OSI layers. Conversely, demultiplexing is the process of separating multiplexed data channels at the destination. One example of multiplexing is when data from multiple applications is multiplexed into a single lower-layer data packet. Figure 1-18 illustrates this example.

Figure 1-18 Multiple Applications Can Be Multiplexed into a Single Lower-Layer Data Packet

Another example of multiplexing is when data from multiple devices is combined into a single physical channel (using a device called a multiplexer). Figure 1-19 illustrates this example.

Figure 1-19 Multiple Devices Can Be Multiplexed into a Single Physical Channel

A multiplexer is a physical layer device that combines multiple data streams into one or more output channels at the source. Multiplexers demultiplex the channels into multiple data streams at the remote end and thus maximize the use of the bandwidth of the physical medium by enabling it to be shared by multiple traffic sources.

Some methods used for multiplexing data are time-division multiplexing (TDM), asynchronous time-division multiplexing (ATDM), frequency-division multiplexing (FDM), and statistical multiplexing.

In TDM, information from each data channel is allocated bandwidth based on preassigned time slots, regardless of whether there is data to transmit. In ATDM, information from data channels is allocated bandwidth as needed by using dynamically assigned time slots. In FDM, information from each data channel is allocated bandwidth based on the signal frequency of the traffic. In statistical multiplexing, bandwidth is dynamically allocated to any data channels that have information to transmit.
Standards Organizations

A wide variety of organizations contribute to internetworking standards by providing forums for discussion, turning informal discussion into formal specifications, and proliferating specifications after they are standardized.

Most standards organizations create formal standards by using specific processes: organizing ideas, discussing the approach, developing draft standards, voting on all or certain aspects of the standards, and then formally releasing the completed standard to the public.

Some of the best-known standards organizations that contribute to internetworking standards include these:

•International Organization for Standardization (ISO)—ISO is an international standards organization responsible for a wide range of standards, including many that are relevant to networking. Its best-known contribution is the development of the OSI reference model and the OSI protocol suite.

•American National Standards Institute (ANSI)—ANSI, which is also a member of
the ISO, is the coordinating body for voluntary standards groups within the United States. ANSI developed the Fiber Distributed Data Interface (FDDI) and other communications standards.

•Electronic Industries Association (EIA)—EIA specifies electrical transmission standards, including those used in networking. The EIA developed the widely used EIA/TIA-232 standard (formerly known as RS-232).

•Institute of Electrical and Electronic Engineers (IEEE)—IEEE is a professional organization that defines networking and other standards. The IEEE developed the widely used LAN standards IEEE 802.3 and IEEE 802.5.

•International Telecommunication Union Telecommunication Standardization Sector (ITU-T)—Formerly called the Committee for International Telegraph and Telephone (CCITT), ITU-T is now an international organization that develops communication standards. The ITU-T developed X.25 and other communications standards.

•Internet Activities Board (IAB)—IAB is a group of internetwork researchers who discuss issues pertinent to the Internet and set Internet policies through decisions and task forces. The IAB designates some Request For Comments (RFC) documents as Internet standards, including Transmission Control Protocol/Internet Protocol (TCP/IP) and the Simple Network Management Protocol (SNMP).
Summary

This chapter introduced the building blocks on which internetworks are built. Under-standing where complex pieces of internetworks fit into the OSI model will help you understand the concepts better. Internetworks are complex systems that, when viewed as a whole, are too much to understand. Only by breaking the network down into the conceptual pieces can it be easily understood. As you read and experience internetworks, try to think of them in terms of OSI layers and conceptual pieces.

Understanding the interaction between various layers and protocols makes designing, configuring, and diagnosing internetworks possible. Without understanding of the building blocks, you cannot understand the interaction between them.

Packet Tracer 5.0

2008-12-18T00:53:00.000-08:00

original article at: http://www.cisco.com/web/learning/netacad/course_catalog/PacketTracer.html

Packet Tracer 5.0
New Version Offers Multiuser Capabilities for Social Learning

Packet Tracer 5.0 is the latest version of Cisco Networking Academy’s comprehensive networking technology teaching and learning software. Innovative features of Packet Tracer 5.0, including powerful simulation, visualization, authoring, assessment, and collaboration capabilities, will help students and teachers collaborate, solve problems, and learn concepts in an engaging and dynamic social environment.

Packet Tracer makes both teaching and learning easier - instructors and students can create their own virtual “network worlds” for exploration, experimentation, and explanation of networking concepts and technologies.

Instructors can demonstrate technologies and configurations using Packet Tracer to teach complex CCNA-level networking concepts, making it extremely useful for lectures, group and individual labs, assessments, troubleshooting and modeling tasks, homework, games, and competitions.
Students can design, configure and troubleshoot networks using Packet Tracer’s versatile simulation and visualization environment, which also provides the opportunity and flexibility for additional practice outside of the classroom environment.

Packet Tracer supplements classroom equipment and provides students complementary learning opportunities that are not physically possible to create in the classroom or lab. In addition, Packet Tracer supplements the CCNA curricula and Packet Tracer activities are integrated throughout both CCNA Discovery and CCNA Exploration to provide rich networking technology learning experiences.

Packet Tracer 5.0 offers a unique combination of realistic simulation and visualization experiences, complex assessment and activity authoring capabilities, and opportunities for multiuser collaboration and competition, and is available free of charge to all Networking Academy instructors, students, and alumni. Visit the Packet Tracer 5.0 resource page under the course catalog on Academy Connection today to download this free software and explore the new possibilities in networking education.

download : http://packet-tracer.software.informer.com/download/

TRANSPORTER 3 PREVIEW

2008-12-17T19:46:00.002-08:00

TRANSPORTER 3 PREVIEW

SMALLVILLE SEASONS 8 PREVIEW

2008-12-17T19:46:00.000-08:00

SMALLVILLE SEASONS 8 PREVIEW

Heroes 3 Preview

2008-12-17T01:38:00.000-08:00

Heroes 3 Preview

Naruto Shipudden 2 the movie : Bonds (preview)

2008-12-17T01:03:00.000-08:00

Wireless Technologies

2008-12-17T00:44:00.000-08:00

original article at : http://www.cisco.com/en/US/docs/internetworking/technology/handbook/wireless.html

Wireless Technologies

Types of Wireless Technology

Eighteen major types of wireless technologies exist, containing a large number of subset technologies that range from ATM-protocol based (which sells at approximately $200,000 per data link, to wireless local-area network (WLAN, which sells at less than $500,000 per data link). Frequencies of the different technologies travel between several hundred feet (wireless LAN) and 25 miles (MMDS).

The process by which radio waves are propagated through the air, the amount of data carried, immunity to interference from internal and external sources, and a host of other characteristics varies from technology to technology.

Wireless technologies are differentiated by the following:

•Protocol—ATM or IP

•Connection type—Point-to-Point (P2P) or multipoint (P2MP) connections

•Spectrum—Licensed or unlicensed

Table 20-1 lists the different wireless technologies.

Table 20-1 Different Types of Wireless Technologies
Broadband¹	Narrowband
WAN	WAN and WLAN
Licensed²	Unlicensed
Digital	Analog
Line-of-site³	Non-line-of-site
Simplex⁴	Half-/full-Duplex
Point-to-point	Multipoint

¹Broadband—Data rates that exceed 1.5 Mbps

²Licensed—Granted by or purchased from the FCC

³Line-of-site—Direct line of site between two antennae

⁴Simplex—One transmitter

Base Station

The base station (also referred to as the hub or the cell site) is the central location that collects all traffic to and from subscribers within a cell. The indoor base station equipment consists of channel groups. The channel groups each connect to the existing network, typically with a DS-3 with ATM signaling. The function of the channel group is to effectively act as a high-speed radio modem for the DS-3 traffic. The outdoor base station equipment (Tx/Rx node) modules are located on a tower or a rooftop mount and consist of a frequency translation hardware and transmitters/receivers. The Tx/Rx node delivers and collects all the traffic to and from subscribers within a cell or a sector. Additionally, the Tx/Rx node equipment translates the channel group output into the appropriate frequency for over-the-air transmission. Multiple channel groups are used in each sector to meet the traffic demands, thus providing a highly scalable architecture.

Introduction to QAM

Many modern fixed microwave communication systems are based on quadrature amplitude modulation (QAM). These systems have various levels of complexity.

Simpler systems such as phase shift keying (PSK) are very robust and easy to implement because they have low data rates. In PSK modulation, the shape of the wave is modified in neither amplitude nor frequency, but rather in phase. The phase can be thought of as a shift in time. In binary phase shift keying (BPSK), the phases for the sine wave start at either 0 or 1/4. In BPSK modulation, only 1 bit is transmitted per cycle (called a symbol). In more complex modulation schemes, more than 1 bit is transmitted per symbol. The modulation scheme QPSK (quadrature phase shift keying) is similar to the BPSK. However, instead of only two separate phase states, QPSK uses four (0, 1/2 ¼, ¼, and 3/2 ¼), carrying 2 bits per symbol. Like BPSK, QPSK is used because of its robustness. However, because it modulates only 2 bits per symbol, it still is not very efficient for high-speed commun-ications. Hence, higher bit rates require the use of significant bandwidth.

Even though QPSK uses no state changes in amplitude, it is sometimes referred to as 4-QAM. When four levels of amplitude are combined with the four levels of phase, we get 16-QAM. In 16 QAM, 2 bits are encoded on phase changes, and 2 bits are encoded on amplitude changes, yielding a total of 4 bits per symbol.

In Figure 20-1, each unique phase is spaced equally in both the I and Q coordinates. The angle of rotation indicates the phase, and the distance from the center point indicates the amplitude. This approach to modulation can be expanded out to 64-QAM and 256-QAM or higher. Although 64-QAM is very popular in both cable and wireless broadband products, 256-QAM is also being tested. The higher the density in QAM, the higher a signal-to-noise (s/n) ratio must be maintained to meet the required bit-error rates (BERs).

Figure 20-1 Error Rates for PSK and QAM Systems

How the data is encoded also plays an important part in the equation. The data is usually scrambled, and a significant amount of forward error correction (FEC) data is also transmitted. Therefore, the system can recover those bits that are lost because of noise, multipath, and interference. A significant improvement in BER is achieved using FEC for a given SNR at the receiver. (See Figure 20-2.)

Figure 20-2 BER Against Signal-to-Noise for Coded and Uncoded Data Streams

Advanced Signaling Techniques Used to Mitigate Multipath

Several techniques have been used to make digital modulation schemes more robust: QAM with decision feedback equalization (DFE), direct sequence spread spectrum (DSSS), frequency-division multiplexing (FDM), and orthogonal frequency-division multiplexing (OFDM).

QAM with DFE

In wireless QAM systems, DFE is used to mitigate the effects of the intersymbol interference (ISI) caused by multipath. When delay spread is present, the echoes of previous symbols corrupt the sampling instant for the current symbol. The DFE filter oversamples the incoming signal and filters out the echoed carriers. The complexity of DFE schemes causes them not to scale with increases in bandwidth. The complexity of the DFE filter (number of taps) is proportional to the size of the delay spread. The number of required taps is proportional to the delay spread (in seconds) multiplied by the symbol rate.

For a QAM-based wireless system transmitting in the MMDS band (6-MHz-wide channel) to survive a 4-µsec delay spread, the number of taps required would equal 24. To equalize a system with 24 taps, a DFE system would need 72 feedforward and 24 feedback taps. In addition to the number of taps needed, the complexity of the math needed for each tap increases with the number of taps. Therefore, the increase in complexity becomes an exponential function of the bandwidth of the carrier signal. Figure 20-3 compares the complexity rate of QAM/DFE and OFDM. Orthogonal frequency-division multiplexing (OFDM) is discussed later in this paper.

Figure 20-3 Computational Complexity of QAM Versus OFDM

Spread Spectrum

Spread spectrum is a method commonly used to modulate the information into manageable bits that are sent over the air wirelessly. Spread spectrum was invented by Heddy Lamar, a film actress who still retains the patent to this day and was the relatively recent recipient of a governmental award for this accomplishment.

Essentially, spread spectrum refers to the concept of splitting information over a series of radio channels or frequencies. Generally, the number of frequencies is in the range of about 70, and the information is sent over all or most of the frequencies before being demodulated, or combined at the receiving end of the radio system.

Two kinds of spread spectrum are available:

•Direct sequence spread spectrum (DSSS)

•Frequency hopping spread spectrum (FHSS)

DSSS typically has better performance, while FHSS is typically more resilient to interference.

A commonly used analogy to understand spread spectrum is that of a series of trains departing a station at the same time. The payload is distributed relatively equally among the trains, which all depart at the same time. Upon arrival at the destination, the payload is taken off each train and is collated. Duplications of payload are common to spread spectrum so that when data arrives excessively corrupted, or fails to arrive, the redundancies inherent to this architecture provide a more robust data link.

Direct sequence spread spectrum (DSSS) is a signaling method that avoids the complexity and the need for equalization. Generally, a narrowband QPSK signal is used. This narrowband signal is then multiplied (or spread) across a much wider bandwidth. The amount of spectrum needed is expressed as: 10(SNR/10) ¥ narrowband symbol rate.

Therefore, if a SNR of 20 dB is required to achieve the appropriate BER, the total spread bandwidth needed to transmit a digital signal of 6 Mbps equals 600 MHz.

This is not very bandwidth-efficient. In addition, the sampling rate for the receiver needs to be about 100 times the data rate. Therefore, for this hypothetical system, the sampling rate would also need to be 600 megasamples per second.

With DSSS, all trains leave in an order beginning with Train 1 and ending with Train N, depending on how many channels the spread spectrum system allocates. In the DSSS architecture, the trains always leave in the same order, although the numbers of railroad tracks can be in the hundreds or even thousands.

Code division multiple access (CDMA) is used to allow several simultaneous transmissions to occur. Each data stream is multiplied with a pseudorandom noise code (PN code). All users in a CDMA system use the same frequency band. Each signal is spread out and layered on top of each other and is overlaid using code spreading in the same time slot. The transmitted signal is recovered by using the PN code. Data transmitted by other users looks like white noise and drops out during the reception phase. Any narrowband noise is dispersed during the de-spreading of the data signal. The advantage of CMDA is that the amount of bandwidth required is now shared over several users. However, in systems in which there are multiple transmitters and receivers, proper power management is needed to ensure that one user does not overpower other users in the same spectrum. These power management issues are mainly confined to CMDA architectures.

FHHS

With the FHSS architecture, the trains leave in a different order—that is, not sequentially from Train 1 to Train N. In the best of FHSS systems, trains that run into interference are not sent out again until the interference abates. In FHSS systems, certain frequencies (channels) are avoided until the interference abates.

Interference tends to cover more than one channel at a time. Therefore, DSSS systems tend to lose more data from interference as the data sent out is done so over sequential channels. FHSS systems hop between channels in nonsequential order. The best of FHSS systems adjust channel selection so that highly interfered channels are avoided as measured by excessively low bit error rates. Either approach is appropriate and depends on customer requirements, with the selection criteria primarily being that of a severe multipath or interfering RF environment.

FDM

In a frequency-division multiplexing (FDM) system, the available bandwidth is divided into multiple data carriers. The data to be transmitted is then divided among these subcarriers. Because each carrier is treated independently of the others, a frequency guard band must be placed around it. This guard band lowers the bandwidth efficiency. In some FDM systems, up to 50 percent of the available bandwidth is wasted. In most FDM systems, individual users are segmented to a particular subcarrier; therefore, their burst rate cannot exceed the capacity of that subcarrier. If some subcarriers are idle, their bandwidth cannot be shared with other subcarriers.

OFDM

In OFDM (see Figure 20-4), multiple carriers (or tones) are used to divide the data across the available spectrum, similar to FDM. However, in an OFDM system, each tone is considered to be orthogonal (independent or unrelated) to the adjacent tones and, therefore, does not require a guard band. Because OFDM requires guard bands only around a set of tones, it is more efficient spectrally than FDM. Because OFDM is made up of many narrowband tones, narrowband interference will degrade only a small portion of the signal and has no or little effect on the remainder of the frequency components.

Figure 20-4 Example of OFDM Tones

OFDM systems use bursts of data to minimize ISI caused by delay spread. Data is transmitted in bursts, and each burst consists of a cyclic prefix followed by data symbols. An example OFDM signal occupying 6 MHz is made up of 512 individual carriers (or tones), each carrying a single QAM symbol per burst. The cyclic prefix is used to absorb transients from previous bursts caused by multipath signals. An additional 64 symbols are transmitted for the cyclic prefix. For each symbol period, a total of 576 symbols are transmitted by only 512 unique QAM symbols per burst. In general, by the time the cyclic prefix is over, the resulting waveform created by the combining multipath signals is not a function of any samples from the previous burst. Hence, there is no ISI. The cyclic prefix must be greater than the delay spread of the multipath signals. In a 6-MHz system, the individual sample rate is 0.16 µsecs. Therefore, the total time for the cyclic prefix is 10.24 µsecs, greater than the anticipated 4 µsecs delay spread.

VOFDM

In addition to the standard OFDM principles, the use of spatial diversity can increase the system's tolerance to noise, interference, and multipath. This is referred to as vectored OFDM, or VOFDM (see Figure 20-5). Spatial diversity is a widely accepted technique for improving performance in multipath environments. Because multipath is a function of the collection of bounced signals, that collection is dependent on the location of the receiver antenna. If two or more antennae are placed in the system, each would have a different set of multipath signals. The effects of each channel would vary from one antenna to the next, so carriers that may be unusable on one antenna may become usable on another. Antenna spacing is at least ten times the wavelength.

Significant gains in the S/N are obtained by using multiple antennae. Typically, a second antenna adds about 3 dB in LOS and up to 10 dB in non-LOS environments.

Figure 20-5 Spectrum Technology

Benefits of Using Wireless Solutions

The following list summarizes the main benefits of using wireless technologies:

•Completes the access technology portfolio—Customers commonly use more than one access technology to service various parts of their network and during the migration phase of their networks, when upgrading occurs on a scheduled basis. Wireless enables a fully comprehensive access technology portfolio to work with existing dial, cable, and DSL technologies.

•Goes where cable and fiber cannot—The inherent nature of wireless is that it doesn't require wires or lines to accommodate the data/voice/video pipeline. As such, the system will carry information across geographical areas that are prohibitive in terms of distance, cost, access, or time. It also sidesteps the numerous issues of ILEC colocation.

Although paying fees for access to elevated areas such as masts, towers, and building tops is not unusual, these fees, the associated logistics, and contractual agreements are often minimal compared to the costs of trenching cable.

•Involves reduced time to revenue—Companies can generate revenue in less time through the deployment of wireless solutions than with comparable access technologies because a wireless system can be assembled and brought online in as little as two to three hours.

This technology enables service providers to sell access without having to wait for cable-trenching operations to complete or for incumbent providers to provide access or backhaul.

•Provides broadband access extension—Wireless commonly both competes with and complements existing broadband access. Wireless technologies play a key role in extending the reach of cable, fiber, and DSL markets, and it does so quickly and reliably. It also commonly provides a competitive alternative to broadband wireline or provides access in geographies that don't qualify for loop access.

Earth Curvature Calculation for Line-of-Sight Systems

Line-of-sight systems that carry data over distances in excess of 10 miles require additional care and calculations. Because curvature of the Earth causes bulges at the approximate rate of 10 feet for every 18 miles, a calculation is required to maintain line-of-sight status.

The Fresnel (pronounced fren-NEL) zone refers to that which must clear the Earth's bulge and other obstructions. This is the elliptically shaped free space area directly between the antennae. The center area in this zone is of the greatest importance and is called the first Fresnel zone. Although the entire Fresnel zone covers an area of appreciable diameter between the antennae, the first Fresnel zone is considered as a radius about the axis between the antennae. A calculation is required to determine the radius (in feet) that must remain free from obstruction for optimal data transfer rates. The formula for this calculation is: D2/8.

Table 20-22 helps to calculate the distance/bulge ratio.

Table 20-2 Wireless Distance Calculations
Distance (Miles)	Earth Bulge
8	8.0
10	12.5
12	18.0
14	24.5
16	32.0

While observing these calculations, it's important to remember that this accounts only for Earth bulge. Vegetation such as trees and other objects such as buildings must have their elevations added into this formula. A reasonable rule of thumb is 75 feet of elevation at both ends of the data link for a distance of 25 miles, but this should be considered an approximation only.

Rft = 72.1 ¥ the square root of d1 ¥ d2 / F¥D

Where:

Rft = radius of the first Fresnel zone in feet

F = carrier frequency

d1 = distance from the transmitter to the first path obstacle

d2 = distance from the path obstacle to the receiver

D = d1 + d2 (in miles)

The industry standard is to keep 60 percent of the first Fresnel zone clear from obstacles. Therefore, the result of this calculation can be reduced by up to 60 percent without appreciable interference. This calculation should be considered as a reference only and does not account for the phenomenon of refraction from highly reflective surfaces.

Non-Line-of-Sight Wireless: Overcoming Multipath in Non-Line-of-Sight High-Speed

Microwave Communication Links

Since the beginning of development of microwave wireless transmission equipment, manufacturers and operators have tried to mitigate the effects of reflected signals associated with signal propagation. These reflections are called multipath. In real-world situations, microwave systems involve careful design to overcome the effects of multipath. Most existing multipath mitigation approaches fall well short of the full reliable information rate potential of many wireless communications systems. This section discusses how to create a digital microwave transmission system that not only can tolerate multipath signals, but that also can actually take advantage of them.

Digital microwave systems fall into two categories: wavelengths less than 10 GHz and wavelengths greater than 10 GHz (referred to as millimeterwave). Several bands exist below 10 GHz for high-speed transmissions. These may be licensed bands, such as MMDS (2.5 GHz), or unlicensed bands, such as U-NII (5.7 GHz). Bands that are below 10 GHz have long propagation distances (up to 30 miles). They are only mildly affected by climatic changes such as rain. These frequencies are generally not absorbed by objects in the environment. They tend to bound and thus result in a high amount of multipath.

Bands over 10 GHz, such as 24 GHz, LMDS (28 GHz), and 38 GHz, are very limited to distance (less than 5 miles). They are also quite susceptible to signal fades attributed to rain. Multipath tends not to be an issue because the transmission distances are less and because most of the multipath energy is absorbed by the physical environment. However, when these frequencies are used in highly dense urban areas, the signals tend to bounce off objects such as metal buildings or metalized windows. The use of repeaters can add to the multipath propagation by delaying the received signal.

What Is Multipath?

Multipath is the composition of a primary signal plus duplicate or echoed images caused by reflections of signals off objects between the transmitter and the receiver. In Figure 20-6, the receiver hears the primary signal sent directly from the transmission facility, but it also sees secondary signals that are bounced off nearby objects.

These bounced signals will arrive at the receiver later than the incident signal. Because of this misalignment, the out-of-phase signals will cause intersymbol interference or distortion of the received signal. Although most of the multipath is caused by bounces off tall objects, multipath can also occur from bounces off low objects such as lakes and pavement.

Figure 20-6 Multipath Reception

The actual received signal is a combination of a primary signal and several echoed signals. Because the distance traveled by the original signal is shorter than the bounced signal, the time differential causes two signals to be received. These signals are overlapped and combined into a single one. In real life, the time between the first received signal and the last echoed signal is called the delay spread, which can be as high as 4 µsec.

In the example shown in Figure 20-7, the echoed signal is delayed in time and reduced in power. Both are caused by the additional distance that the bounced signal traveled over the primary signal. The greater the distance, the longer the delay and the lower the power of the echoed signal. You might think that the longer the delay, the better off the reception would be. However, if the delay is too long, the reception of an echoed symbol S1 and the primary symbol S2 can also interact. Because there may be no direct path for the incident signal in non-line-of-sight (LOS) environments, the primary signal may be small in comparison to other secondary signals.

Figure 20-7 Typical Multipath Example

In analog systems such as television, this multipath situation can actually be seen by the human eye. Sometimes there is a ghost image on your television, and no matter how much you adjust the set, the image does not go away. In these analog systems, this is an annoyance. In digital systems, it usually corrupts the data stream and causes loss of data or lower performance. Correction algorithms must be put in place to compensate for the multipath, resulting in a lower available data rate.

In digital systems, the input signal is sampled at the symbol rate. The echoed signal actually interferes with the reception of the second symbol, thus causing intersymbol interference (ISI). This ISI is the main result of multipath, and digital systems must be designed to deal with it.

Multipath in Non-LOS Environments

In LOS environments, multipath is usually minor and can be overcome easily. The amplitudes of the echoed signals are much smaller than the primary one and can be effectively filtered out using standard equalization techniques. However, in non-LOS environments, the echoed signals may have higher power levels because the primary signal may be partially or totally obstructed, and generally because more multipath is present. This makes the equalization design more difficult.

In all the previous discussions, the multipath has been a semifixed event. However, other factors such as moving objects enter into play. The particular multipath condition changes from one sample period to the next. This is called time variation. Digital systems must be capable of withstanding fast changes in the multipath conditions, referred to as fast fading. To deal with this condition, digital systems need fast AGC circuits. Adaptive equalizers, discussed next, need fast training times.

Elements of a Total Network Solution

The issue of what comprises a solution is the subject of considerable discussion and conjecture. Commonly, the term solution includes the following primary elements:

•Premises networks

•Access networks

•Core networks

•Network management

•Billing/OSS

A fully comprehensive wireless solution must also include the issues of deployment, maintenance, legacy, migration, and value propositions. The scope of what comprises a fully comprehensive solution can readily exceed these items.

Premises Networks

Premises networks are the voice, data, or video distribution networks that exist or will exist within the subscriber premises. Typical points of demarcation between the access and premises networks for purposes of this discussion include channel banks, PBXs, routers, or multiservice access devices.

Customer premises equipment receives signals from the hub, translates them into customer-usable data, and transmits returning data back to the hub. The transmitter, the receiver, and the antenna are generally housed in a compact rooftop unit (RTU) that is smaller than a satellite TV minidish. It is mounted on the subscriber's roof in a location where it will have a clear line of sight to the nearest LMDS hub site. Installation includes semiprecision pointing to ensure maximum performance of the RF link.

The indoor unit, the network interface unit (NIU), does the modulation, demodulation, in-building wire-line interface functions, and provides an intermediate frequency to the RTU. Many interfaces required by end customer equipment require the NIU to have a breadth of physical and logical interfaces. The NIUs are designed to address a range of targeted subscribers whose connectivity requirements may range from T1/E1, POTS, Ethernet, or any other standard network interface. These interfaces are provided by the NIU with interworking function (IWF) cards. Different types of IWF cards are required in the NIU to convert the inputs into ATM cells and provide the appropriate signaling. Common IWFs include 10BaseT, T1/E1 circuit emulation, and others. The NIU also has an IF that is translated by the CPE RTU.

Access Networks

The access networks are the transport and distribution networks that bridge the premises network and the core network demarcation points. For purposes of this discussion, the primary means of providing the transport from an access network point-of-presence (POP) to the premises is radio and the distribution between access network POPs is either fiber or radio.

Core Networks

The core networks are the public or private backbone networks that, in a general sense, will be utilized by the access network operators to connect their multitude of regionally dispersed POPs and to interconnect to public service provider network elements. For purposes of this discussion, the point of demarcation between the access network and the core network is a core switch that serves as an upstream destination point for a multitude of access network branches or elements.

Network Management

The glue that ties all the network elements together and supports the key information processing tasks that make a business run effectively is performed by the Network Management System (NMS) inclusive of Operational Support System (OSS) functionality. In its full implementation, the NMS is an exceptionally complex set of moderately to highly integrated software platforms. For the purposes of this document, the element managers necessary within each system-level piece of the access network are assumed, but the overarching NMS is beyond the intended scope of this document.

Ideally, the NMS should provide end-to-end functionality throughout both the wireless and wireline elements of the network, including the backbone and the customer premises. A network management system performs service, network, and element management across multivendor and multitechnology networks, including these:

•Topology management

•Connectivity management

•Event management

The functions of the network management system can be further outlined as follows:

•Integrated topology map that displays an entire set of nodes and links in the network, shown with mapped alarms

•Store of network-wide physical (nodes/links) and logical topology (circuits/PVCs) for inventory

•Customer care interface to provide network and end-user status

•Performance statistics on PCR, SCR, MBS, CDVT, and network/link status

•SLA reporting with customer partitioning, and alerting of customer violations

•Alarm correlation and root-cause analysis

•Network simulation to test whether a problem was completely corrected

•Trouble ticketing/workforce management

•Performance reports based on statistics collected, with customer and network views

•Usage-based billing for ATM connections

•Read-only CNM for viewing network and connection

Deployment

As stated previously, tier 1 customers will utilize Cisco's ecosystem of deployment partners. Deployment for systems covering BTA, MTA, or nationwide footprints requires the following areas of expertise and resources:

•Construction (towers, masts)

•Licensing (FCC and local compliance for RF, construction, and access)

•Site survey (RF environment evaluation)

•Integration (selection and acquisition of various RF compenents)

•Prime (customer engagement through contract)

•Finance (securing or provisioning of project financing)

•Installation (assembly of components)

•Provisioning (spare components)

Billing and Management of Wireless Systems

The issue of billing and network management is a considerable one. In the most general terms, you should consider the wireless links as a network section managed by the standard Cisco IOS and SNMP tools. Accordingly, key customer items such as billing, dynamic host control, testing, and configuration are managed remotely with standard router tools, as indicated in Figure 20-8.

Figure 20-8 Management Interfaces

Example Implementation

Cisco's MMDS/U-NII system is designed with the following objectives:

•For a service provider to offer differentiated services via wireless access, the wireless access system should offer higher capacity than alternative access technologies.

•The capacity of the system is increased by three items:

–A highly efficient physical layer that is robust to interference, resulting in high bandwidth efficiency per sector

–A statistically efficient industry standard Medium Access Control (MAC) protocol that delivers quality of service (QoS)

–A multicellular system

•Large bandwidth enables differentiated services such as Voice over IP (VoIP) now, and interactive video in the future, both with QoS.

•A multitiered CPE approach, satisfying the needs of small and medium businesses (SMB), small office/home office (SOHO) applications, and residential customers.

•Ease of base installation and back-haul.

•Ease of provisioning and network management.

IP Wireless System Advantages

Table 20-3 summarizes the advantages of the proposed system.

Table 20-3 Features and Benefits of Wireless Communication
Feature	Benefit
Shared-bandwidth system	Point-to-multipoint wireless architecture Shared bandwidth among many small and medium businesses Burst data rate up to 22 Mbps
Dedicated high-bandwidth System	Point-to-point wireless architecture High data rate (22 to 44 Mbps) Shared head end with point-to-multipoint equipment
Small-cell and single-cell deployment	Variety of available cellular deployment plans Capability to scale with successful service penetration from tens of customers to thousands of customers Single cells of up to 45-km radius Small cells of up to 10-km radius for maximum revenue
Third-generation microwave technology	Higher-percentage coverage of customers in business district Capability of non-line-of-sight technology to service customers that older technology cannot service Capability to configure marginal RF links to improve performance Tolerant of narrow-band interference Receivers capable of adapting to changing environment for every packet Licensed frequency band Options that include unlicensed 5.7- to 5.8-GHz band
Open interfaces	Part of Cisco's dedication to open architectures Partners capable of supplying outdoor unit (ODU), antenna, cable, and all other components outside the router Availability of in-country manufacturers as partners Capability of MAC protocol to enhance DOCSIS, a proven industry multipoint standard
Integrated into Cisco routers	IOS system software and Cisco management software features that treat the radio link as simply another WAN interface Two systems created in one unit: a radio and a multiservice router Wireless integrated into management, provisioning, and billing systems Minimized cost of spare hardware
Native IP	Voice over IP Video over IP Virtual private networks Quality of service Queuing features Traffic policies
Cost-effective solution	Competitively priced Large pool of personnel already trained on Cisco routers and protocols Reduced training time Addition of broadband wireless access to Cisco's total end-to-end network solution and support
Link encryption	Privacy ensured through use of 40/56-bit DES encryption on every user's wireless link

IP Wireless Services for Small and Medium Businesses

The small to medium business (SMB) customer requires services that range from typical Internet data access to business voice services. Most small businesses today have separate voice and data access lines. Almost all SMB customers use native IP in their networks. Voice access lines are typically analog POTS lines or key telephone system (KTS) trunks. As businesses grow, they may require a digital T1 trunk for their private branch exchange (PBX). Data access is typically anything from dial to ISDN, fractional T1 Frame Relay, and potentially up to a dedicated leased line T1 service.

•SMB access technologies include these:

–Plain Old Telephone Service (POTS)

–KTS trunks

–Digital T1 PBX trunks

–Internet data access (Fast Ethernet)

•SMB service technologies include these:

–Internet access (IP service)

–Intranet access (VPN)

–Voice services (VoIP)

–Videoconferencing

–Service-level agreements for guaranteed data rates

•Residential access offerings include these:

–POTS

–Internet data access

•Residential service offerings include these:

–Internet access (IP service)

–Intranet access

–Voice services (VoIP)

–Videoconferencing

IP Point-to-MultiPoint Architecture

The point-to-multipoint (P2MP) system consists of a hub, or head end (HE), or a base station (BS),¹ which serves several sectors in the cell. Each sector consists of one radio communicating with many customers.

The head end is an outdoor unit, or transverter, connected to a wireless modem card inside a Cisco UBR7246 or 7223 router.

At the customers' premises is another transverter, which is connected to a wireless network module in a router.

Cisco P2MP objectives are these:

•Integrated end-to-end solution (one box, one management and provisioning platform)

•Complete multiservice offering (Voice over IP, data, Video over IP)

•Scalability and flexibility (scalable head end and CPE offerings)

•Enabled for non-line-of-sight (substantially better coverage)

•Native IP packet transport

•Part of an overall standards-based strategy to provide many Cisco hosts and many frequency bands on a global basis

The shared-bandwidth, or multipoint, product delivers 1 to 22 Mbps aggregate full-duplex, shared-bandwidth, P2MP fixed-site data in the MMDS band for both residential and small business applications, as shown in Figure 20-9.

The P2MP wireless router will be an integrated solution. At the base station (or head end, or hub), it will consist of a base universal router (UBR 7246 or UBR7223), a wireless modem card, an outdoor unit (ODU) for the appropriate frequency band, cables, and antenna subsystems, as shown in Figure 20-10.

At the small business customer premises, the system consists of a network module in a 3600-family router, with an outdoor unit (ODU) and antenna. This CPE equipment is simpler and, therefore, less expensive than the head end (HE) equipment. The 3600 family has a wide variety of interfaces to match all types of customer equipment.

At the SOHO or telecommuter customer premises, the system consists of a network module in a 2600- or 900-family router, with an outdoor unit (ODU) and an antenna. This CPE equipment is simpler and, therefore, less expensive than the head end (HE) equipment. The 2600 and 900 families have a wide variety of interfaces to match all types of customer equipment. A consumer unit by one or more of Cisco's ecosystem partners is expected by the first quarter of 2001.

These wireless broadband routers (WBBR) are then used to blanket an urban area by dividing the business district into small cells.

The product will also be capable of working as a single cell—that is, one hub serving an entire business district in a cell of radius less than 45-miles, because the low frequencies in the MMDS band are not impacted by rain. However, a single cell does not have the revenue potential of small cells. See the section "Title" for the revenue generation potential of these two alternatives.

Figure 20-9 Basic Components of the P2MP Base Station (Head End, Hub)

Figure 20-10 The Cisco MMDS Broadband Wireless Access System

Technology has always been a Cisco Systems differentiator, and the proposed system fits that market position. The proposed P2MP system uses patented third-generation microwave technology to overcome the classical microwave constraint that the transmitter and receiver must have a clear line of sight. The proposed technology takes advantage of waves that bounce off buildings, water, and other objects to create multiple paths from the transmitter to the receiver. The receivers are capable of making all these multipath signals combine into one strong signal, rather than having them appear to be interference.

The capability to operate with high levels of multipath permits obstructed links to be deployed. This, in turn, enables multicellular RF deployments and virtually limitless frequency reuse. Also, the antennae in the system can be mounted on short towers or rooftops.

Although this is primarily a savings in the cost of installing a system, it has the added benefit of making the installation less visible to the user's neighbors, which is very important in some regions.

The typical point-to-multipoint system for an SMB is shown in Figure 20-11.

The point-to-point system is similar, except that the customer premises equipment is another UBR7223 or 7246 router. The point-to-point system is shown in Figure 20-12.

Some SMB customers will require a data rate that is higher than the service provider can supply within the traffic capacity of the multipoint system. The service provider may satisfy those customers by installing Cisco's point-to-point (P2P) links from the same hub as the P2MP system. Thus, the hub can be a mixture of P2MP and P2P systems.

In both cases, integrating the wireless card directly into the router brings with it all the Cisco IOS features and network management.

Figure 20-11 Hardware Components of the Point-to-Point System (Only One of Four Possible Sectors Shown on HE Equipment)

IP Wireless Open Standards

This open architecture permits many different vendors to participate, creating new products, features, and services. Figure 20-13 shows why many vendors will be interested in this approach. By using a common IF, many different frequency bands can be utilized for many different services.

Other router and switch vendors will also be capable of entering the market because the IF-to-WAN conversion is something that they can work into their product line. It also shows how Cisco will migrate the IF into WAN interfaces in a range of existing and future router products.

Equally important, by making the wireless interface just one more WAN interface on a router, Cisco has integrated all the network management for the wireless system into the normal router and switch network management, such as CiscoView and CiscoWorks2000.

Figure 20-12 Hardware Components of the Point-to-Point System

Figure 20-13 Open Standard Wireless Architecture

IP Vector Orthogonal Frequency-Division Multiplexing

The system uses the next-generation microwave technology invented by Cisco Systems, called vector orthogonal frequency-division multiplexing (VOFDM), to resolve the issue of multipath signals in a radiating environment.

A transmitted signal will reflect off buildings, vegetation, bodies of water, and large, solid surfaces, causing ghosts of the carrier (main or intentional) frequency to arrive at the receiver later than the carrier frequency.

Multipath signal issues are a liability for all radio systems except those without VOFDM or a feature to cancel or filter the late-arriving signals.

Embedded in the OFDM-modulated carrier frequencies are training tones. These allow multipath-channel compensation on a burst-by-burst basis. This is especially important on the uplink because each OFDM burst may be transmitted by a different subscriber unit (SU) over a different multipath channel. The overall effect of the VOFDM scheme is an RF system that is extremely resilient to multipath signals.

Multiple Access and Error Control Schemes

This section describes various multiple access techniques and error control schemes.

Channel Data Rate

Raw channel over-the-air data rates are 36, 24, 18, 12, 9, and 6 Mbps. Excluding physical layer overhead, the user rates are different for the downstream and upstream links. Downstream, these rates are 22.4, 17, 12.8, 10.1, 7.6, and 5.1 Mbps. Upstream, the rates are 19.3, 15.2, 11.4, 8.1, 6.2, 4.4, 4.2, 3.2, and 1.4 Mbps. Various combinations of these rates are supported, depending on the cell type.

These are configuration parameters that can be set and changed. Thus, if a customer requests an increased data rate service, the change can be made from the network operations center (NOC) without personnel having to visit the customer site.

The service provider can make this as simple or as complicated as desired. Thus, one service city can have all subscribers on a single data rate plan, while another city can offer time-of-day and day-of-week data rate premium services.

Downstream and Upstream User Bandwidth Allocation

Downstream and upstream user bandwidth can be assigned dynamically for session-based traffic or, during initial registration for best-effort Internet data access, based on service flows for each user.

Duplexing Techniques

Time-division duplexing and frequency-division duplexing are the two common techniques used for duplexing. There are challenges with each of the two approaches, related to implementation, flexibility, sensitivity, network synchronization, latency, repeaters, asymmetrical traffic, AGC, and the number of SAW filters, among others. After a study of the subject, it was decided that the TDD vs. FDD selection is not a simple decision to make—indeed, the advantage marks are relatively close to one another. However, having the benefit of the most recent information regarding the procurement of low-cost duplexors, development priority was given to FDD scheme.

TDD is a duplexing technique that utilizes time sharing to transmit and receive data in both directions. Each side is allotted a certain amount of time to transmit, generally in symmetric amounts. The TDD algorithms are embedded into each of the RF processor boards and are synched by protocol instruction when the units are first powered up. Commonly these synching protocols are updated on a routine basis.

In FDD, the total allocated spectrum of frequency is divided so that each end of the radio link can transmit in parallel with the other side. FDD is commonly divided equally, but it is not symmetric on many links.

Multiple Access Technique

User bandwidth allocation is carried out by means of a Medium Access Control (MAC) protocol. This protocol is based on the MAC portion of DOCSIS protocol developed by the Cable Labs consortium. The MAC protocol assigns service flows (SID) to each user; depending on the quality of service (QoS) requirements, the upstream MAC scheduler provides grants to fulfill the bandwidth needs. Similarly, the downstream bandwidth is divided between active users of unicast and multicast services.

Each upstream channel is divided into intervals. Intervals are made up of one or more minislots. A minislot is the smallest unit of granularity for upstream transmit opportunities.

Upstream transmit opportunities are defined by the MAC MAP message. This message is sent from the base station to all registered CPEs. In the MAP message, each interval is assigned a usage code that defines the type of traffic that can be transmitted during that interval, as well as whether the interval is open for contention by multiple CPEs or for the sole use of one CPE. The interval types are request, request/data, initial maintenance, station maintenance, short data grant, long data grant, and acknowledgment.

For example, the request interval is used for CPE bandwidth requests and is typically multicast to all CPEs; therefore, it is an interval open for contention. Multiple CPEs can attempt to send a bandwidth request; if the request is granted, the base station will assign a series of minislots to the CPE in the next MAP message. Contention is resolved via a truncated binary exponential back-off algorithm.

Figure 20-14 Frame Allocation MAP

To support customer QoS requirements, six types of service flows are specified: Unsolicited Grant Service (UGS), real-time Polling Service (rtPS), Unsolicited Grant Service with Activity Detection (UGS-AD), non-real-time Polling Service (nrtPS), Best Effort (BE) Service, and a Committed Information Rate (CIR) Service.

Unsolicited Grant Service

The intent of UGS is to reserve fixed-size data grants at periodic transmission opportunities for specific real-time traffic flows. The MAC scheduler provides fixed-size data grants at periodic intervals to the service flow. The QoS parameter for the given service flow sets the grant size, the nominal grant interval, and the tolerant grant jitter.

Real-Time Polling Service

The intent of the rtPS grants is to reserve upstream transmission for real-time traffic flows such as VoIP. Such service flows receive periodic transmission opportunities regardless of network congestion, but they release their transmission reservation when they are inactive. As such, the base station MAC scheduler sends periodic polls to rtPS service flows using unicast request opportunities enabling subscriber wireless port to request for the upstream bandwidth that it needs. The QoS parameter for such a service flow is nominal polling interval and the jitter tolerance for the request/grant policy.

Unsolicited Grant Service with Activation Detection

The intent of UGS-AD is to reserve upstream transmission opportunities for real-time traffic flows such as VoIP with silence suppression. USG-AD is designed to emulate the capabilities of UGS service when active, and rtPS service when inactive. The QoS parameter for such a service flow is nominal polling interval, tolerated polling jitter, nominal grant interval, tolerated grant jitter, unsolicited grant size, and the request/transmission policy.

Non-Real-Time Polling Service

The intent of nrtPS is to set aside upstream transmission opportunities for non-real-time traffic flows such as FTP transfer. These service flows receive a portion of transmission opportunities during traffic congestion. The base station MAC scheduler typically polls such service flows either in a periodic or a nonperiodic fashion. The subscriber wireless port can use either the unicast request opportunities or contention request opportunities to request upstream grants. The QoS parameter for such a service flow is nominal polling interval, reserved minimum traffic rate, maximum allowed traffic rate, traffic priority, and request/transmission policy.

Best Effort Service

The intent of the BE service is to provide an efficient way of transmission for best-effort traffic. As such, the subscriber wireless port will use either contention or unicast request opportunities to request upstream grants. The QoS parameter for such a service flow is reserved minimum traffic rate, maximum sustained traffic rate and traffic priority.

Committed Information Rate

CIR can be implemented in several different ways. As an example, it could be a BE service with a reserved minimum traffic rate, or nrtPS with a reserved minimum traffic rate.

Frame and Slot Format

The frame and slot format is based on the MAC protocol. The downstream transmission is broadcast, similar to Ethernet, with no association with framing or a minislot. The recipients of downstream packets perform packet filtering based on the Layer 2 address—the Ethernet MAC or SID value.

The upstream transmission is based on a time-division multiple access (TDMA) scheme, and the unit of time is a minislot. The minislot size varies based on upstream configuration settings and can carry data between 8 bytes and approximately 230 bytes. TDMA synchronization is done by time-stamp messages, and the time of transmission is communicated to each subscriber by the MAP messages (a MAP message carries the schedule information (map) for each minislot of the next data protocol data unit (PDU)). MAP messages are initiated by the MAC scheduler in the base station and thus convey how each minislot is used (reserved for user traffic, for initial invitation, or as contention slots). The contention slots are used for best-effort traffic to request bandwidth from the scheduler. The frame time is programmable and can be optimized for a given network.

Synchronization Technique (Frame and Slot)

Accurately receiving an orthogonal frequency-division multiplexing (OFDM) burst requires burst timing and frequency offset estimation. Burst timing means determining where in time the OFDM burst begins and ends. Determining the difference between the local demodulating oscillator and the modulating oscillator at the transmitter is called frequency synchronization, or frequency offset estimation.

Burst timing and frequency offset are determined simultaneously through the use of the extra-cyclic-prefix samples in every downstream OFDM burst. Regardless of the channel, the samples in the extra-cyclic-prefix will be equal to a set of time-domain samples in the OFDM burst. This structure is optimally exploited to simultaneously identify the correct OFDM burst timing and frequency offset. These estimates are then filtered over successive OFDM bursts.

Burst timing and frequency synchronization are required for the downstream link. The upstream link will be frequency locked once the subscriber unit frequency locks the downstream signal. That is, the local oscillator at the subscriber unit is synchronized to the base station oscillator by use of a frequency-locked loop. In this way, the upstream transmission that arrives at the base station receiver will have nearly zero frequency offset.

As in any TDMA upstream, each subscriber unit must lock to the TDMA slot when transmitting on the upstream. This is referred to as ranging each subscriber. As prescribed by the MAC layer, a subscriber fills periodic ranging slots with a known sequence. This known sequence is used at the base station to determine proper slot timing.

The upstream TDMA synchronization is done via time-stamp messages that carry the exact timing of the base station clock. Each subscriber phase locks its local clock to the base station clock and then synchronizes its minislot (unit of TDMA) counter to match that of the base station. Furthermore, ranging is performed as part of initial acquisition to advance the transmission time of the subscriber so that the precise arrival of its transmission is synchronized with the expected minislot time of the base station.

Average Overall Delay over Link

The average overall delay in the link depends on the particular bandwidth and spectral efficiency setting. In all cases, the physical layer delay is limited to 5 ms in the downstream. The upstream physical layer delay is less than 2 ms.

Power Control

Power control is done in real time to track rapidly changing environment. It is one facet of the system capability to adjust on a packet-by-packet basis.

The power control is capable of adjusting for fades as deep as 20 dB.

Receiver signal power at the subscriber is controlled through the use of an Automatic Gain Control (AGC) system. The AGC system measures received power at the analog-to-digital converter (ADC) and adaptively adjusts the analog attenuation. With AGC, channel gain variations on the order of 200 Hz can be accommodated without impacting the OFDM signal processing.

Receive power at the base station is regulated through the use of an Automatic Level Control (ALC) system. This system measures power levels of each subscriber and creates transmit attenuator adjustments at the subscriber so that future communication is done with the correct transmit power level. This power control loop is implemented in the physical layer hardware so as not to impact the MAC-layer performance.

Power measurements for the purposes of ALC occur on upstream traffic. Specific power bursts may be requested by the base station MAC to power control subscribers.

Admission Control

A new user is admitted to the system by means of a software suite. Components of this suite are User Registrar, Network Registrar, Modem Registrar, and Access Registrar.

User Registrar enables wireless network subscribers to self-provision via a web interface. Subscriber self-provisioning includes account registration and activation of the subscriber's CPE and personal computers over the wireless access network. User Registrar activates subscriber devices with account-appropriate privileges through updates to an LDAPv3 directory.

Network Registrar supplies DHCP and DNS services for the CPEs and personal computers. Network Registrar DHCP allocates IP addresses and configuration parameters to clients based on per-device policies, which are obtained from an LDAP directory. Network Registrar allocates limited IP addresses and default configuration parameters to inactivated devices, to steer users to the User Registrar activation page.

Modem Registrar adds TFTP and time services to Network Registrar for the CPEs. The Modem Registrar TFTP builds DOCSIS configuration files for clients based on per-CPE policies, which are obtained from an LDAP directory. Modem Registrar builds limited-privilege configuration files to inactivated CPEs.

Access Registrar supplies RADIUS services for the CPEs and the clients that are connected to the CPEs. Access Registrar RADIUS returns configuration parameters to NAS clients based on per-subscriber policies, which are obtained from an LDAP directory. Access Registrar returns limited-privilege NAS and PPP parameters to unregistered subscribers and to inactivated CPEs.

Requirement to Cell Radius

As stated previously, the system employs frequency-division duplexing (FDD). Unlike time-division multiplexing (TDD) systems, the equipment is not subject to cell radius limits. The only limitation to cell radius is that imposed by free space attenuation (FSA) of the radio signals. Timing limitations imposed by the MAC protocol on upstream and downstream channels would permit the cell radius to be beyond the radio horizon (FSA notwithstanding).

Unless the subscriber density is very low, as in rural areas, very large cells are not recommended because they may quickly become capacity-limited and are difficult to scale to meet the higher capacity demand.

Requirement for Frequency Reuse

Two architectures are described in this section. The first is a multicellular architecture, called the small-cell pattern. The second architecture is known as a single-cell architecture. The baseline small-cell architecture employs a 4 ¥ 3 frequency reuse pattern. This means that a four-cell reuse pattern and three sectors are employed within each cell or base station (BS). Within a cellularized network, a hexagonal cell is tiled out to completely cover the service area. In our system, a four-cell tiling pattern is repeated over the service area. This tiling pattern puts a lower limit on the reuse distance, thereby controlling interference levels. Employing three sectors within each BS further reduces interference compared to omnidirectional antennae. A 4 ¥ 3 reuse pattern works well for operations using obstructed (OBS) links. It uses a total of 24 channels: 12 channels downstream, plus 12 channels upstream.

Note that the number of MMDS channels used may be different than 12 + 12 because the system supports channels narrower than 6 MHz. At any given BS, signals are received from subscriber units (SUs) over both OBS links and line-of-sight (LOS) links. In general, OBS links are attenuated at 40 dB/decade; that is, R-4 path loss. LOS links, however, propagate based on R-2 path loss. Thus, if an SU has a LOS link to its BS, it likely also has a LOS link to a reuse BS. To suppress cochannel interference from LOS links, horizontal and vertical polarization are alternatively used on reuse cells. This results in an overall reuse scheme of 4 ¥ 3 ¥ 2 and (still) using a total of 24 channels. This reuse pattern can be continued to cover as large a geographical area as desired. Improved frequency reuse can occur when networks are of more limited extent. This is because there are fewer tiers of interfering cells. In these cases, greater C/I ratios are obtained, along with greater network capacity (given a fixed amount of spectrum).

Our approach to frequency reuse for OBS links is conservative in that it does not rely on polarization discrimination. Signals transmitted over multipath channels often experience depolarization. If a dual polarization reuse scheme were employed, it may be very difficult to achieve 99.99 percent link availability because as a reuse (undesired) channel is depolarized, it results in higher levels of interference to the cochannel (desired) signal.

Radio Resource Management

Radio resource management falls under the following broad categories:

•Spectrum management in a cell

•Load balancing of CPEs within an upstream channel

•Time-slotted upstream architecture

•Contention resolution

•Traffic policing

•Traffic shaping

•Quality of service controls

Spectrum Management in a Cell

Within a cell, the upstream frequency band can be split into as many as four channels. The channel bandwidths that can be configured are 1.5 MHz, 3 MHz, and 6 MHz. The downstream frequency consists of one channel that again can be configured as one of 1.5, 3, or 6 MHz. The capability of the Cisco wireless products to operate in these wide ranges of channel bandwidths allows the operator great flexibility in designing the network for efficient usage.

Load Balancing of CPEs Within an Upstream Channel

A cell within the Cisco wireless access architecture consists of a downstream channel with up to four upstream 1.5-MHz channels. By default, load balancing is performed on the upstream channels as CPEs enter the network. Special algorithms run on CPE and the head end to ensure a uniformity of CPE loading on the upstream channels. This allocation of CPEs across the upstream channels can also be done under user control.

Time-Slotted Upstream

Cisco's wireless access solution uses a MAC protocol based on DOCSIS. This protocol is based on a broadcast downstream architecture and a time-slotted upstream architecture. The time slots for the upstream govern the access rights of each CPE on to the upstream channel. There is a very sophisticated scheduler that runs on the head end and allocates these time slots to all the CPEs. Resource sharing of the upstream bandwidth is realized by each CPE making its request to send in a contention time slot, the head end responding to it in a subsequent message downstream (called a MAP message), and the CPE using the information in the MAP message to send the data in an appropriate time slot upstream.

Contention Resolution

The DOCSIS protocol uses the notion of contention time slots in the upstream. These time slots are used by the CPEs to send a request to the head end for a time slot grant to send data. In a loaded upstream network, it is possible for these contention slots to become very congested themselves and nonproductive. Cisco's wireless head end uses an intelligent algorithm to ensure that the contention slots are evenly spaced, especially in times of high upstream load. The CPEs also implement an intelligent algorithm that ensures that the request grants from the CPEs are spaced evenly over all the contention slots in a given MAP message.

Traffic Policing

One of the most important features of the wireless access channel is its shared nature. At any given time, several hundreds or thousands of CPE subscribers may be sharing an upstream or downstream channel. Although this shared nature is useful for reducing the per-subscriber investment for the operator, two important aspects must be considered while providing this access service:

•The need to allocate this bandwidth fairly among all the users

•The need to prevent misbehaving users from completely monopolizing the access

The Cisco solution uses sophisticated algorithms at the head end to police the traffic from each subscriber CPE.

Traffic Shaping

The traffic from each CPE can also be shaped by algorithms running at the head end. This allows the operator to provision services to the CPE based on the critical nature of the traffic, customer needs, and so on. The peak rates of traffic from each subscriber are measured on a continuous basis and are policed at every request from the CPE. If the request from the CPE exceeds its allotted rate, the grant is delayed, thereby effectively controlling the rate of data transfer from the CPE. Differentiated services can be offered to subscribers. The operator can configure different maximum data rates for different wireless subscribers and can charge accordingly. Subscribers requiring higher peak rates and willing to pay for the same can be configured with a higher peak rate limit dynamically or statically.

Interface Specifications Based on the Generic Reference Model

We will use the generic reference model in Figure 20-15. In this figure, reference points I-VIII refer to specific interfaces and/or functions. We describe each of these interfaces or functions below.

Figure 20-15 Generic Reference Model for Broadband Wireless Access

•Interface I: Wireless Subscriber Interface

•Interface II: Subscriber Indoor Unit PHY/MAC Interface

•Interface III: Subscriber Radio IF/RF Interface—This interface is a physical coaxial cable carrying IF, digital control information, and DC powering for the ODU.

•Interface IV: RF Air Interface—This interface is the over-the-air RF interface. It is in the MMDS frequency band (2.500 to 2.690 GHz, and 2.150 to 2.162 GHz). The energy radiated from the antenna is governed by FCC Rules and Regulations, Part 21.

The above descriptions of interfaces I to III represent Cisco Systems products by way of example. Such products will interwork with the base station described next, via interface IV compatibility, but will have many new and different CPE interfaces, features, and services.

•Interface V: Base Station RF/IF Interface—This interface at the base station is a physical coaxial cable carrying intermediate frequency (IF), digital control information, and DC powering for the outdoor unit (ODU).

•Interface VI: Base Station Indoor PHY/MAC Interface—This interface is internal to the Cisco router.

•Interface VII: Network Connection Interface

Wireless Protocol Stack

The access wireless architecture consists of a base station system that serves a community of subscriber systems. It is a point-to-multipoint architecture in the sense that the entire bandwidth on the upstream and downstream is shared among all the subscribers. The protocol stack implemented to make all this work is based on the DOCSIS standards developed by the Cable Labs consortium.

The current state of the art is the version by Cisco that includes a base station end (a UBR7200 router); the subscriber end is in the 3600 or a 900 router series. The base station end and the subscriber end operate as forwarding agents and also as end systems (hosts). As forwarding agents, these systems can also operate in bridging or routing mode. The principal function of the wireless system is to transmit Internet Protocol (IP) packets transparently between the base station and the subscriber location. Certain management functions also ride on IP that include, for example, spectrum management functions and the software downloading.

Both the subscriber end and the base station end of the wireless link are IP hosts on a network, as shown in Figure 20-16, and they fully support standard IP and Logical Link Control (LLC) protocols, as defined by the IEEE 802 LAN/MAN Standards Committee standards. The IP and Address Resolution Protocol (ARP) protocols are supported over DIX and SNAP link layer framing. The minimum link layer minimum transmission unit (MTU) on transmit from the base station is 64 bytes; there is no such limit for the subscriber end. IEEE 802.2 support for TEST and XID messages is provided.

The primary function of the wireless system is to forward packets. As such, data forwarding through the base station consists of transparent bridging or network layer forwarding such as routing and IP switching. Data forwarding through the subscriber system is link layer transparent bridging as with Layer 3 routing based on IP. Forwarding rules are similar to [ISO/IEC10038], with modifications as described in DOCSIS specifications Section 3.1.2.2 and Section 3.1.2.3. Both the base station end and the subscriber end support DOCSIS-modified spanning-tree protocols and include the capability to filter 802.1d bridge PDUs (BPDUs). The DOCSIS specification also assumes that the subscriber units will not be connected in a configuration that would create network loops.

Both the base station end and the subscriber end provide full support for Internet Group Management Protocol (IGMP) multicasting.

Above the network layer, the subscribers or end users can use the transparent IP capability as a bearer for higher-layer services. Use of these services will be transparent to the subscriber end and the base station end.

In addition to the transport of user data, several network management and operation capabilities are supported by the base station end and the subscriber end:

•Simple Network Management Protocol (SNMP), [RFC-1157], for network management

•Trivial File Transfer Protocol (TFTP), [RFC-1350], a file transfer protocol, for downloading software and configuration information, as modified by RFC 2349, "TFTP Timeout Interval and Transfer Size Options" [RFC-2349]

•Dynamic Host Configuration Protocol (DHCP), [RFC-2131], a framework for passing configuration information to hosts on a TCP/IP network

•Time of Day Protocol [RFC-868], to obtain the time of day

Figure 20-16 Wireless Protocol Stack for Network Management and Operation

Link layer security is provided in accordance with DOCSIS baseline privacy specifications.

System Performance Metrics

Table 20-4 shows the network capacity for High Capacity Suburban/Urban Small-Cell Network.

Table 20-4 Network Capacity for High-Capacity Suburban/Urban Small-Cell Network
Cell Radius (Mile)	No. of Cells	Small Businesses Served	Small Business Penetration	Households Served	Household Penetration
2.2	83	5,229	10.5%	126,990	15.9%

These capacities are based on 6-MHz downstream channels and 3-MHz upstream channels:

•Downstream—6 MHz; at the medium VOFDM-throughput setting, 17.0 Mbps.

•Upstream—3.0 MHz; at the low VOFDM-throughput setting, 4.4 Mbps. The low setting has been chosen so that both SB and residential SUs may be serviced by the same upstream channels.

This high-capacity network has 83 cells in the network, each with 3 sectors. A total of 249 sectors are in the network, each serving 21 SB and 510 HH. Overall, a total of 249 ¥ 21, or 5,229, SBs are served by the network; similarly, a total of 126,990 HHs are served.

This network design graphically illustrates the power and scalability of Cisco's technology.

Supercell Network Design

The supercell (very large cell) network design is one that provides low coverage and low overall network capacity. However, it may be attractive for initial network rollout because of the availability of existing (tall) towers. In our supercell design, assuming that a sufficient number of MMDS channels are available, up to 18 sectors may be used. No frequency reuse is performed within the supercell, again because of sector-to-sector isolation requirements that are greater than sector antennae can provide. Each sector operates independently. Also, at least four MMDS-channels must be set aside as guard bands.

The number of sectors deployed on the supercell may be scaled as the demand for capacity grows. Because there is no frequency reuse, no special requirements are placed on the design of the sector antennae. For example, the same panel antenna used for a 3-sector supercell could also be used all the way up to 18 sectors. However, to increase RF coverage, narrower-beam antennae may be employed to increase EIRP. This will be effective as long as the supercell isn't capacity-limited (which is often the case).

The capacity of the supercell is given in Table 20-5. In this deployment model, we have not differentiated between suburban and urban deployments. The assumption is that the desire is to provide service primarily to subscribers in which LOS operation is possible. Because macrodiversity is not possible in a supercell design, coverage becomes difficult. For example, the COST-231 Hata model predicts an 80 percent coverage at a radius of only 15 miles—much smaller than the desired cell radius. Moreover, this coverage is computed at the limits of the model's antenna heights—200 m for the HE, and 10 m for the SU over suburban terrain.

Table 20-5 Network Capacity for Supercell
Number of Sectors	Cell Radius (Mile)	Small Businesses Served	Small Business Penetration	Households Served	Household Penetration
3	16	1,116	2%	26,856	3%
18	23	2,232	4%	53,712	7%

These capacities are based on 6-MHz downstream channels and 3-MHz upstream channels, both at the medium VOFDM-throughput setting.

If a lower availability objective were desired, the fade margin could be greatly reduced, thereby extending the cell radius. More importantly, the sector-to-sector isolation would be greatly reduced, perhaps admitting frequency reuse within the supercell. Because the cell is capacity-limited (there are many more subscribers in the cell's radio footprint than there is capacity to service), this would be a tremendous benefit.

The multipath channel from both the front (desired) antenna and the rear (undesired) antenna must be the same so that the fading from the desired and undesired antennae must be highly correlated.

The time rate-of-change of the multipath channel must be slow enough such that power control errors are very small.

The following sections present both the general functions performed by the various configuration items or building blocks segmented into transport and services products.

Transport Layer Products

The transport layer is composed of the equipment that provides the transmission and reception of IF signals between the rooftop and router equipment and the RF signals over the air. The transport equipment is designed to work in an outdoor environment mounted on buildings or telecommunications towers. The P2MP transport layer is physically segmented into hub and terminal equipment categories, as depicted in Figure 20-17.

Figure 20-17 Hub Site Equipment (Per Sector)

P2MP Transport Equipment Element—Customer Premises

The terminal equipment consists of an integrated RF transceiver/antenna, commonly referred to as the rooftop unit (RTU). This equipment is easily installed on any customer rooftop using a standard mounting device. The RTU requires two RG-11 coaxial cables to the indoor equipment for transmit, receive, and power. The RTU operates on 12.5VDC (nominal) at the input and in standard configuration must be installed within 60 m of the network interface unit (NIU), although longer spans can be engineered and supported.

Rooftop Unit

The sole element of the P2MP transport layer at the terminal site is the RTU. The RTU is an integrated antenna and RF transceiver unit that provides wireless transmission and reception capabilities in the 5.7 GHz frequency region. Received and transmitted signals are frequency translated between the 5.7 GHz region and an intermediate frequency (IF) in the 400 MHz range to the network interface unit (NIU).

The RTU consists of an antenna(s), a down-converter/IF strip, and an up-converter/transmitter. It receives/transmits using orthogonal polarization. Selection of polarization (horizontal/vertical) occurs at installation and is dictated by the hub-sector transmitter/receiver. This selection remains fixed for the duration that service is provided to that site.

The RTU mounts on the exterior of a subscriber's building. Some alignment is required to gain line of sight (LOS) to the hub serving the RTU. Multiple RTUs can be deployed to provide path redundancy to alternate hub sites. The RTU requires dual coax cable (RG-11) runs to the NIU for signal and power. The maximum standard separation between the RTU and the NIU is 60 m. This separation can be extended via application-specific designs.

Basic Receiver

A single basic receiver is required per 90° sector, if no return-path redundancy is required. The receive module is an integrated 5.7-GHz receiver/down-converter/antenna. A collection of signals is received from customer units operating in the 5.7 GHz band and is block down-converted to an intermediate frequency signal. This signal is provided to any of the channel group types. Vertical or horizontal polarization is selectable, and a redundant receiver per sector can be deployed as an option.

High-Gain Receiver

A high-gain receiver is used in lieu of the basic receiver when higher link margin is required because of the specific geographic conditions of deployment. The high-gain receive module is intended to be matched only with the high-gain transmit module. The specifications are identical to those of the basic receive module, except for physical package and antenna gain.

Because of the modularity of the SP2200 products, there is no one standard rack or set of racks. All SP2200 elements are designed to mount in a standard 19-inch (48.3-cm) open relay rack with a standard EIA hole pattern or an equipment enclosure with 19 inches (48.3 cm) of horizontal equipment mounting space. Final assembly of the equipment into racks is accomplished on site at initial install or over time as capacity demands.

LMDS Environmental Considerations

Environmental conditions such as rain and smog must be considered when deploying RF systems that transmit at frequencies above 10 GHz because these conditions degrade the signal path and shorten the maximum range for a given data link.

LMDS data links are generally about one-fourth that of MMDS or U-NIII links and require fairly strict adherence to a line-of-sight implementation. One of the more favorable aspects of the LMDS frequency, however, is that it has exceptional frequency reuse capabilities.

Data link availability is expressed in terms of the number of nines that follow the decimal point. For example, 99.999 percent link availability means that a data link will be up and online (available) for all but .001 percent of the year. Link availability is dependent on a wide range of items, but these generally begin with fundamental RF system design issues such as antenna size, range between antennae, and atmospheric conditions (for LMDS band).

WLAN Standards Comparison

Table 20-6 provides a brief comparison of WLAN standards.

Table 20-6 A Brief Comparison of HomeRF, Bluetooth, and 802.11 WLAN Standards
	HomeRF	Bluetooth	802.11
Physical Layer	FHSS¹	FHSS	FHSS, DSSS², IR³
Hop Frequency	50 hops per second	1600 hops per second	2.5 hops per second
Transmitting Power	100 mW	100 mW	1W
Data Rates	1 or 2 Mbps	1 Mbps	11 Mbps
Max # Devices	Up to 127	Up to 26	Up to 26
Security	Blowfish format	0-, 40-, and 64-bit	40- to 128-bit RC4
Range	150 feet	30 to 300 feet	400 feet indoors, 1000 feet LOS
Current Version	V1.0	V1.0	V1.0

¹FHSS-frequency hopping spread spectrum

²DSSS-direct sequence spread spectrum

³IR-infrared

The following should be noted in Table 20-6:

•40- to 128-bit RC4 refers to very robust data security algorithms.

•An 802.11 range of 1,000 feet refers to outdoor conditions. Indoor conditions are more difficult for these types of RF systems.

•802.11 power output of 1W is substantial.

•The maximum number of devices supported depends on data rate per device.

•The Aironet acquisition uses 802.11.

Although there are three standards in use in the United States, and an additional two are in use in Europe (HyperLAN and HyperLAN2), the FCC thinks highly of the 802.11b standard, and a close relationship exists between the FCC and the IEEE, which backs the standard.

Summary

At least 18 different types of wireless are in commercial use today. Therefore, as this technology becomes more mainstream, users will need to be increasingly specific in their reference to the term. The different types of wireless are quite unique to each other on numerous levels, and they require specific types of expertise to deploy, use, and maintain.

In its state-of-the-art deployment, a wireless link emulates all the capabilities of a fully featured router, which means that a wireless link can provide VPN, enterprise toll bypass, and MDU/MTU access services. This is one of the primary differences between a Layer 2 product as provided by the majority of wireless vendors and the Layer 3 solution provided by Cisco Systems.

Regardless of the provider of a wireless system, the fundamental elements remain relatively constant:

•Data or network

•Edge or access router

•DSP medium

•RF medium (coax, modulator/demodulator, antenna)

•RF management software

Like every access medium or technology, wireless has its pros and cons. The pros include these:

•It's much less expensive to deploy than trenching for cabling.

•It's much quicker to deploy—a link can be up in a couple of hours.

•Wireless can go where cables can't, such as mountainous or inaccessible terrain.

•Less red tape is involved for deployment, if roof rights or elevation access is available.

•It involves an inherent high degree of security, and additional security layers can be added.

•Wireless provides broadband mobility, portability that tethered access doesn't provide.

Simple Network Management Protocol

2008-12-17T00:29:00.000-08:00

Original Article at : http://www.cisco.com/en/US/docs/internetworking/technology/handbook/SNMP.html

Simple Network Management Protocol

Background

The Simple Network Management Protocol (SNMP) is an application layer protocol that facilitates the exchange of management information between network devices. It is part of the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite. SNMP enables network administrators to manage network performance, find and solve network problems, and plan for network growth.

Two versions of SNMP exist: SNMP version 1 (SNMPv1) and SNMP version 2 (SNMPv2). Both versions have a number of features in common, but SNMPv2 offers enhancements, such as additional protocol operations. Standardization of yet another version of SNMP—SNMP Version 3 (SNMPv3)—is pending. This chapter provides descriptions of the SNMPv1 and SNMPv2 protocol operations. Figure 56-1 illustrates a basic network managed by SNMP.

Figure 56-1 SNMP Facilitates the Exchange of Network Information Between Devices

SNMP Basic Components

An SNMP-managed network consists of three key components: managed devices, agents, and network-management systems (NMSs).

A managed device is a network node that contains an SNMP agent and that resides on a managed network. Managed devices collect and store management information and make this information available to NMSs using SNMP. Managed devices, sometimes called network elements, can be routers and access servers, switches and bridges, hubs, computer hosts, or printers.

An agent is a network-management software module that resides in a managed device. An agent has local knowledge of management information and translates that information into a form compatible with SNMP.

An NMS executes applications that monitor and control managed devices. NMSs provide the bulk of the processing and memory resources required for network management. One or more NMSs must exist on any managed network.

Figure 56-2 illustrates the relationships of these three components.

Figure 56-2 An SNMP-Managed Network Consists of Managed Devices, Agents, and NMSs

SNMP Basic Commands

Managed devices are monitored and controlled using four basic SNMP commands: read, write, trap, and traversal operations.

The read command is used by an NMS to monitor managed devices. The NMS examines different variables that are maintained by managed devices.

The write command is used by an NMS to control managed devices. The NMS changes the values of variables stored within managed devices.

The trap command is used by managed devices to asynchronously report events to the NMS. When certain types of events occur, a managed device sends a trap to the NMS.

Traversal operations are used by the NMS to determine which variables a managed device supports and to sequentially gather information in variable tables, such as a routing table.

SNMP Management Information Base

A Management Information Base (MIB) is a collection of information that is organized hierarchically. MIBs are accessed using a network-management protocol such as SNMP. They are comprised of managed objects and are identified by object identifiers.

A managed object (sometimes called a MIB object, an object, or a MIB) is one of any number of specific characteristics of a managed device. Managed objects are comprised of one or more object instances, which are essentially variables.

Two types of managed objects exist: scalar and tabular. Scalar objects define a single object instance. Tabular objects define multiple related object instances that are grouped in MIB tables.

An example of a managed object is atInput, which is a scalar object that contains a single object instance, the integer value that indicates the total number of input AppleTalk packets on a router interface.

An object identifier (or object ID) uniquely identifies a managed object in the MIB hierarchy. The MIB hierarchy can be depicted as a tree with a nameless root, the levels of which are assigned by different organizations. Figure 56-3 illustrates the MIB tree.

The top-level MIB object IDs belong to different standards organizations, while lower-level object IDs are allocated by associated organizations.

Vendors can define private branches that include managed objects for their own products. MIBs that have not been standardized typically are positioned in the experimental branch.

The managed object atInput can be uniquely identified either by the object name—iso.identified-organization.dod.internet.private.enterprise.cisco.temporary variables.AppleTalk.atInput—or by the equivalent object descriptor, 1.3.6.1.4.1.9.3.3.1.

Figure 56-3 The MIB Tree Illustrates the Various Hierarchies Assigned by Different Organizations

SNMP and Data Representation

SNMP must account for and adjust to incompatibilities between managed devices. Different computers use different data representation techniques, which can compromise the capability of SNMP to exchange information between managed devices. SNMP uses a subset of Abstract Syntax Notation One (ASN.1) to accommodate communication between diverse systems.

SNMP Version 1

SNMP version 1 (SNMPv1) is the initial implementation of the SNMP protocol. It is described in Request For Comments (RFC) 1157 and functions within the specifications of the Structure of Management Information (SMI). SNMPv1 operates over protocols such as User Datagram Protocol (UDP), Internet Protocol (IP), OSI Connectionless Network Service (CLNS), AppleTalk Datagram-Delivery Protocol (DDP), and Novell Internet Packet Exchange (IPX). SNMPv1 is widely used and is the de facto network-management protocol in the Internet community.

SNMPv1 and Structure of Management Information

The Structure of Management Information (SMI) defines the rules for describing management information, using Abstract Syntax Notation One (ASN.1). The SNMPv1 SMI is defined in RFC 1155. The SMI makes three key specifications: ASN.1 data types, SMI-specific data types, and SNMP MIB tables.

SNMPv1 and ASN.1 Data Types

The SNMPv1 SMI specifies that all managed objects have a certain subset of Abstract Syntax Notation One (ASN.1) data types associated with them. Three ASN.1 data types are required: name, syntax, and encoding. The name serves as the object identifier (object ID). The syntax defines the data type of the object (for example, integer or string). The SMI uses a subset of the ASN.1 syntax definitions. The encoding data describes how information associated with a managed object is formatted as a series of data items for transmission over the network.

SNMPv1 and SMI-Specific Data Types

The SNMPv1 SMI specifies the use of a number of SMI-specific data types, which are divided into two categories: simple data types and application-wide data types.

Three simple data types are defined in the SNMPv1 SMI, all of which are unique values: integers, octet strings, and object IDs. The integer data type is a signed integer in the range of -2,147,483,648 to 2,147,483,647. Octet strings are ordered sequences of 0 to 65,535 octets. Object IDs come from the set of all object identifiers allocated according to the rules specified in ASN.1.

Seven application-wide data types exist in the SNMPv1 SMI: network addresses, counters, gauges, time ticks, opaques, integers, and unsigned integers. Network addresses represent an address from a particular protocol family. SNMPv1 supports only 32-bit IP addresses. Counters are non-negative integers that increase until they reach a maximum value and then return to zero. In SNMPv1, a 32-bit counter size is specified. Gauges are non-negative integers that can increase or decrease but that retain the maximum value reached. A time tick represents a hundredth of a second since some event. An opaque represents an arbitrary encoding that is used to pass arbitrary information strings that do not conform to the strict data typing used by the SMI. An integer represents signed integer-valued information. This data type redefines the integer data type, which has arbitrary precision in ASN.1 but bounded precision in the SMI. An unsigned integer represents unsigned integer-valued information and is useful when values are always non-negative. This data type redefines the integer data type, which has arbitrary precision in ASN.1 but bounded precision in the SMI.

SNMP MIB Tables

The SNMPv1 SMI defines highly structured tables that are used to group the instances of a tabular object (that is, an object that contains multiple variables). Tables are composed of zero or more rows, which are indexed in a way that allows SNMP to retrieve or alter an entire row with a single Get, GetNext, or Set command.

SNMPv1 Protocol Operations

SNMP is a simple request/response protocol. The network-management system issues a request, and managed devices return responses. This behavior is implemented by using one of four protocol operations: Get, GetNext, Set, and Trap. The Get operation is used by the NMS to retrieve the value of one or more object instances from an agent. If the agent responding to the Get operation cannot provide values for all the object instances in a list, it does not provide any values. The GetNext operation is used by the NMS to retrieve the value of the next object instance in a table or a list within an agent. The Set operation is used by the NMS to set the values of object instances within an agent. The Trap operation is used by agents to asynchronously inform the NMS of a significant event.

SNMP Version 2

SNMP version 2 (SNMPv2) is an evolution of the initial version, SNMPv1. Originally, SNMPv2 was published as a set of proposed Internet standards in 1993; currently, it is a draft standard. As with SNMPv1, SNMPv2 functions within the specifications of the Structure of Management Information (SMI). In theory, SNMPv2 offers a number of improvements to SNMPv1, including additional protocol operations.

SNMPv2 and Structure of Management Information

The Structure of Management Information (SMI) defines the rules for describing management information, using ASN.1.

The SNMPv2 SMI is described in RFC 1902. It makes certain additions and enhancements to the SNMPv1 SMI-specific data types, such as including bit strings, network addresses, and counters. Bit strings are defined only in SNMPv2 and comprise zero or more named bits that specify a value. Network addresses represent an address from a particular protocol family. SNMPv1 supports only 32-bit IP addresses, but SNMPv2 can support other types of addresses as well. Counters are non-negative integers that increase until they reach a maximum value and then return to zero. In SNMPv1, a 32-bit counter size is specified. In SNMPv2, 32-bit and 64-bit counters are defined.

SMI Information Modules

The SNMPv2 SMI also specifies information modules, which specify a group of related definitions. Three types of SMI information modules exist: MIB modules, compliance statements, and capability statements. MIB modules contain definitions of interrelated managed objects. Compliance statements provide a systematic way to describe a group of managed objects that must be implemented for conformance to a standard. Capability statements are used to indicate the precise level of support that an agent claims with respect to a MIB group. An NMS can adjust its behavior toward agents according to the capabilities statements associated with each agent.

SNMPv2 Protocol Operations

The Get, GetNext, and Set operations used in SNMPv1 are exactly the same as those used in SNMPv2. However, SNMPv2 adds and enhances some protocol operations. The SNMPv2 Trap operation, for example, serves the same function as that used in SNMPv1, but it uses a different message format and is designed to replace the SNMPv1 Trap.

SNMPv2 also defines two new protocol operations: GetBulk and Inform. The GetBulk operation is used by the NMS to efficiently retrieve large blocks of data, such as multiple rows in a table. GetBulk fills a response message with as much of the requested data as will fit. The Inform operation allows one NMS to send trap information to another NMS and to then receive a response. In SNMPv2, if the agent responding to GetBulk operations cannot provide values for all the variables in a list, it provides partial results.

SNMP Management

SNMP is a distributed-management protocol. A system can operate exclusively as either an NMS or an agent, or it can perform the functions of both. When a system operates as both an NMS and an agent, another NMS might require that the system query manage devices and provide a summary of the information learned, or that it report locally stored management information.

SNMP Security

SNMP lacks any authentication capabilities, which results in vulnerability to a variety of security threats. These include masquerading occurrences, modification of information, message sequence and timing modifications, and disclosure. Masquerading consists of an unauthorized entity attempting to perform management operations by assuming the identity of an authorized management entity. Modification of information involves an unauthorized entity attempting to alter a message generated by an authorized entity so that the message results in unauthorized accounting management or configuration management operations. Message sequence and timing modifications occur when an unauthorized entity reorders, delays, or copies and later replays a message generated by an authorized entity. Disclosure results when an unauthorized entity extracts values stored in managed objects, or learns of notifiable events by monitoring exchanges between managers and agents. Because SNMP does not implement authentication, many vendors do not implement Set operations, thereby reducing SNMP to a monitoring facility.

SNMP Interoperability

As presently specified, SNMPv2 is incompatible with SNMPv1 in two key areas: message formats and protocol operations. SNMPv2 messages use different header and protocol data unit (PDU) formats than SNMPv1 messages. SNMPv2 also uses two protocol operations that are not specified in SNMPv1. Furthermore, RFC 1908 defines two possible SNMPv1/v2 coexistence strategies: proxy agents and bilingual network-management systems.

Proxy Agents

An SNMPv2 agent can act as a proxy agent on behalf of SNMPv1 managed devices, as follows:

•An SNMPv2 NMS issues a command intended for an SNMPv1 agent.

•The NMS sends the SNMP message to the SNMPv2 proxy agent.

•The proxy agent forwards Get, GetNext, and Set messages to the SNMPv1 agent unchanged.

•GetBulk messages are converted by the proxy agent to GetNext messages and then are forwarded to the SNMPv1 agent.

The proxy agent maps SNMPv1 trap messages to SNMPv2 trap messages and then forwards them to the NMS.

Bilingual Network-Management System

Bilingual SNMPv2 network-management systems support both SNMPv1 and SNMPv2. To support this dual-management environment, a management application in the bilingual NMS must contact an agent. The NMS then examines information stored in a local database to determine whether the agent supports SNMPv1 or SNMPv2. Based on the information in the database, the NMS communicates with the agent using the appropriate version of SNMP.

SNMP Reference: SNMPv1 Message Formats

SNMPv1 messages contain two parts: a message header and a protocol data unit (PDU). Figure 56-4 illustrates the basic format of an SNMPv1 message.

Figure 56-4 An SNVPv1 Message Consists of a Header and a PDU

SNMPv1 Message Header

SNMPv1 message headers contain two fields: Version Number and Community Name.

The following descriptions summarize these fields:

•Version number—Specifies the version of SNMP used.

•Community name—Defines an access environment for a group of NMSs. NMSs within the community are said to exist within the same administrative domain. Community names serve as a weak form of authentication because devices that do not know the proper community name are precluded from SNMP operations.

SNMPv1 Protocol Data Unit

SNMPv1 PDUs contain a specific command (Get, Set, and so on) and operands that indicate the object instances involved in the transaction. SNMPv1 PDU fields are variable in length, as prescribed by ASN.1. Figure 56-5 illustrates the fields of the SNMPv1 Get, GetNext, Response, and Set PDUs transactions.

Figure 56-5 SNMPv1 Get, GetNext, Response, and Set PDUs Contain the Same Fields

The following descriptions summarize the fields illustrated in Figure 56-5:

•PDU type—Specifies the type of PDU transmitted.

•Request ID—Associates SNMP requests with responses.

•Error status—Indicates one of a number of errors and error types. Only the response operation sets this field. Other operations set this field to zero.

•Error index—Associates an error with a particular object instance. Only the response operation sets this field. Other operations set this field to zero.

•Variable bindings—Serves as the data field of the SNMPv1 PDU. Each variable binding associates a particular object instance with its current value (with the exception of Get and GetNext requests, for which the value is ignored).

Trap PDU Format

Figure 56-6 illustrates the fields of the SNMPv1 Trap PDU.

Figure 56-6 The SNMPv1 Trap PDU Consists of Eight Fields

The following descriptions summarize the fields illustrated in Figure 56-6:

•Enterprise—Identifies the type of managed object generating the trap.

•Agent address—Provides the address of the managed object generating the trap.

•Generic trap type—Indicates one of a number of generic trap types.

•Specific trap code—Indicates one of a number of specific trap codes.

•Time stamp—Provides the amount of time that has elapsed between the last network reinitialization and generation of the trap.

•Variable bindings—The data field of the SNMPv1 Trap PDU. Each variable binding associates a particular object instance with its current value.

SNMP Reference: SNMPv2 Message Format

SNMPv2 messages consist of a header and a PDU. Figure 56-7 illustrates the basic format of an SNMPv2 message.

Figure 56-7 SNMPv2 Messages Also Consist of a Header and a PDU

SNMPv2 Message Header

SNMPv2 message headers contain two fields: Version Number and Community Name.

The following descriptions summarize these fields:

•Version number—Specifies the version of SNMP that is being used.

SNMPv2 Protocol Data Unit

SNMPv2 specifies two PDU formats, depending on the SNMP protocol operation. SNMPv2 PDU fields are variable in length, as prescribed by Abstract Syntax Notation One (ASN.1).

Figure 56-8 illustrates the fields of the SNMPv2 Get, GetNext, Inform, Response, Set, and Trap PDUs.

The following descriptions summarize the fields illustrated in Figure 56-8:

•PDU type—Identifies the type of PDU transmitted (Get, GetNext, Inform, Response, Set, or Trap).

•Request ID—Associates SNMP requests with responses.

•Error status—Indicates one of a number of errors and error types. Only the response operation sets this field. Other operations set this field to zero.

•Error index—Associates an error with a particular object instance. Only the response operation sets this field. Other operations set this field to zero.

•Variable bindings—Serves as the data field of the SNMPv2 PDU. Each variable binding associates a particular object instance with its current value (with the exception of Get and GetNext requests, for which the value is ignored).

Figure 56-8 SNMPv2 Get, GetNext, Inform, Response, Set, and Trap PDUs Contain the Same Fields

GetBulk PDU Format

Figure 56-9 illustrates the fields of the SNMPv2 GetBulk PDU.

Figure 56-9 The SNMPv2 GetBulk PDU Consists of Seven Fields

The following descriptions summarize the fields illustrated in Figure 56-9:

•PDU type—Identifies the PDU as a GetBulk operation.

•Request ID—Associates SNMP requests with responses.

•Non repeaters—Specifies the number of object instances in the variable bindings field that should be retrieved no more than once from the beginning of the request. This field is used when some of the instances are scalar objects with only one variable.

•Max repetitions—Defines the maximum number of times that other variables beyond those specified by the Non repeaters field should be retrieved.

Dynasty Warriors 6

2008-12-08T18:50:00.000-08:00

original article at: http://www.gamespot.com/ps3/action/shinsangokumusou5/review.html

Dynasty Warriors 6 is the first game in Koei's long-running hack-and-slash series to be built specifically for current-generation consoles, and as such it benefits in one major area: It looks pretty. Other than that, this is Dynasty Warriors as it has been since its inception: a huge, sprawling, button-mashing affair set in ancient China, complete with the series' requisite cheesy cutscenes, dozens of playable characters, bad dialogue, and mostly incomprehensible storyline. Of course, there are new gameplay additions in Dynasty Warriors 6, but they're tweaks rather than overhauls and will be more exciting to long-term fans than casual players of the series.

If you are a newcomer, then suffice it to say that the Dynasty Warriors franchise has represented some of the best button-grinding fun to be had on consoles, although the series has been widely criticized for being just that: unashamed, action-focused, and strategy-light games that become almost hypnotic in their repetitiveness. The gameplay in Dynasty Warriors generally consists of your chosen character taking on hundreds of opposing soldiers single-handedly, which is usually accomplished by pressing one or two buttons ad nauseam. Like previous entries in the series, Dynasty Warriors 6 is set in the Three Kingdoms period of ancient China, a time when three rival factions were battling it out for supremacy over the land. You take the role of a general from one of the factions--Wu, Shu, or Wei--and are set loose in large, open battlefield areas to take on an opposing army practically alone. (The kill counts at the end of each level usually number in the hundreds, if not thousands.) Although only nine generals are initially selectable, there are a total of 41 playable characters who become unlocked as you play through the game, a number that is not quite as many as in previous Dynasty Warriors offerings.

Dynasty Warriors 6 doesn't stray far from the series formula.

One of Dynasty Warriors 6's key innovations is the Renbu system, a new way for characters to build up their attack combos. In previous entries in the series, combos were usually tied to the quality of weapon your character was wielding, with more powerful weapons (usually found throughout the course of a campaign) allowing generals longer and longer consecutive attacks. The Renbu system ditches the weapon-based combo count completely and replaces it instead with a gauge that gradually fills as you perform attacks. If you string together enough attacks without getting hit, then your Renbu will go up a level, which in turn lets your character perform a longer combo. If you go too long without attacking or suffer from a serious blow, then your Renbu goes down. This means that characters will be able to perform up to six-hit combos practically from the get-go, although longer strings will still have to be unlocked as you progress through the game and earn more Renbu levels.

Though the ability to do wicked six-string combos from the opening level of the game is all well and good, what the Renbu system really does is make the Dynasty Warriors brand of basic button-mashing even simpler by boiling down a two-button-mashing affair into one. Previous games in the series forced you to use both the normal and charged attack buttons to perform different hit-number combos, but with Renbu, you can now simply press the normal attack button over and over again to come up with flashy-looking and effective moves. (Charged attacks in Dynasty Warriors 6 are now best left for trying to break the block of an enemy.) It doesn't do much to dispel the series' reputation of being a brainless bash-'em-up, but then again Dynasty Warriors has never positioned itself as gaming's version of advanced calculus.

Another major addition to the series is a skill tree that you can use to improve the attributes, attacks, and special abilities of your generals. Generals still earn experience in campaigns and go up in levels, but instead of attributes such as health, defense, and attack improving automatically, you now receive skill points to spend on building a character. Skill points can also be spent on other abilities, such as more Renbu levels, bigger damage to specific attacks, being able to carry more items, and others. There's enough in the skill tree that you won't be able to unlock all of a general's abilities during your first play-through, but it's certainly not as exhaustive as in other games.

The rest of Dynasty Warriors 6's new features, though quite significant in the context of the series, will probably leave everyone who hasn't drunk the Three Kingdoms Kool-Aid scratching their heads, given that they've been staples of many other games for quite a while now. Generals can now--wait for it--climb ladders and swim. Series stalwarts will most likely appreciate the introduction of ladder climbing, which--in addition to the ability to now jump down into lower levels of maps--gives Dynasty Warriors 6 a more multilayered feel. You can send your generals up into castle battlements to take down enemy archers and ballistas, and you can also take a shortcut down a winding mountain path to quickly get behind an enemy unit. Swimming seems less integral, although it's neat to now be able to swim through some of the game's water-based levels (such as in the Battle of Fan Castle) instead of taking a longer but dryer path. In another addition, enemy bases can now be invaded by simply bashing down the door that leads into them, as opposed to finding the appropriate defense captain and sending him sprawling. Duels with enemy generals have also been tweaked somewhat; enemy soldiers now form a cordon around the two combatants during their battle.

With so many generals in the game's lineup, there's plenty of replay value in Dynasty Warriors 6, although the amount of replay you'll get from this really depends on how you feel about doing the same thing and going through the same levels (albeit with a different character) over and over again. If you're fine with the repetition, then there are well over a hundred hours of play to be had in Dynasty Warriors 6, considering that each general's campaign will take roughly three or four hours to complete. Returning in Dynasty Warriors 6 are challenge modes, which task you with performing set tasks such as defeating as many enemies as possible within a set time limit, moving from base to base as quickly as possible, and more. The game also features a two-player, split-screen cooperative mode, although sadly there's no online option whatsoever apart from leaderboards.

All of the generals have benefitted from visual makovers.

Thanks to the power of current-gen consoles, one of the key areas of improvement in Dynasty Warriors 6 is in the looks department. Each of the generals has undergone a complete facelift from previous games, and now all sport snazzy motion-captured moves that make their attacks look more fluid and realistic. The series' dreaded and much-mocked fog of war has also disappeared, which means that Dynasty Warriors 6 has a decent draw distance that lets you see the lay of the land more clearly. However, it's not all sunshine, given that the game--much like every other Dynasty Warriors game before it--still suffers from horrendous pop-ups and pop-outs. Enemy and allied soldiers will routinely just appear out of nowhere while you move through the expansive battlefields, and pieces of the environment (grass in particular) will simply disappear as you get closer to them. And though the game does have many more characters on the screen at once, we encountered several instances of serious slowdown during some of the more hectic scenes. The slowdown wasn't enough to affect gameplay, but it was most definitely notable, particularly when playing two-player split-screen. Where audio is converned the series' cheesy and generic rock soundtrack still dominates. As always, it's mainly uninspiring and seems to have not changed at all from the series' PlayStation 2 days.

There's no question that Dynasty Warriors 6 plays it safe with the series' tried-and-tested formula, which means fans will lap it up, whereas those who tried a previous game and found it not to their liking will find nothing here to change their view. For everyone else, Dynasty Warriors 6 is a decent beat-'em-up with plenty of gameplay packed in.

Routing Information Protocol

2008-12-04T23:35:00.000-08:00

Original Article at :www.cisco.ws/en/US/docs/internetworking/technology/handbook/RIP.html

Routing Information Protocol

Background

The Routing Information Protocol, or RIP, as it is more commonly called, is one of the most enduring of all routing protocols. RIP is also one of the more easily confused protocols because a variety of RIP-like routing protocols proliferated, some of which even used
the same name! RIP and the myriad RIP-like protocols were based on the same set of algorithms that use distance vectors to mathematically compare routes to identify the best path to any given destination address.

These algorithms emerged from academic research that dates back to 1957. Today's open standard version of RIP, sometimes referred to as IP RIP, is formally defined in two documents: Request For Comments (RFC) 1058 and Internet Standard (STD) 56. As IP-based networks became both more numerous and greater in size, it became apparent to the Internet Engineering Task Force (IETF) that RIP needed to be updated. Consequently, the IETF released RFC 1388 in January 1993, which was then superceded in November 1994 by RFC 1723, which describes RIP 2 (the second version of RIP). These RFCs described an extension of RIP's capabilities but did not attempt to obsolete the previous version of RIP. RIP 2 enabled RIP messages to carry more information, which permitted the use of a simple authentication mechanism to secure table updates. More importantly, RIP 2 supported subnet masks, a critical feature that was not available in RIP. This chapter summarizes the basic capabilities and features associated with RIP. Topics include the routing update process, RIP routing metrics, routing stability, and routing timers.

Routing Updates

RIP sends routing-update messages at regular intervals and when the network topology changes. When a router receives a routing update that includes changes to an entry, it updates its routing table to reflect the new route. The metric value for the path is increased by 1, and the sender is indicated as the next hop. RIP routers maintain only the best route (the route with the lowest metric value) to a destination. After updating its routing table, the router immediately begins transmitting routing updates to inform other network routers of the change. These updates are sent independently of the regularly scheduled updates that RIP routers send.

RIP Routing Metric

RIP uses a single routing metric (hop count) to measure the distance between the source and a destination network. Each hop in a path from source to destination is assigned a hop count value, which is typically 1. When a router receives a routing update that contains a new or changed destination network entry, the router adds 1 to the metric value indicated in the update and enters the network in the routing table. The IP address of the sender is used as the next hop.

RIP Stability Features

RIP prevents routing loops from continuing indefinitely by implementing a limit on the number of hops allowed in a path from the source to a destination. The maximum number of hops in a path is 15. If a router receives a routing update that contains a new or changed entry, and if increasing the metric value by 1 causes the metric to be infinity (that is, 16), the network destination is considered unreachable. The downside of this stability feature is that it limits the maximum diameter of a RIP network to less than 16 hops. RIP includes a number of other stability features that are common to many routing protocols. These features are designed to provide stability despite potentially rapid changes in a network's topology. For example, RIP implements the split horizon and holddown mechanisms to prevent incorrect routing information from being propagated.

RIP Timers

RIP uses numerous timers to regulate its performance. These include a routing-update timer, a route-timeout timer, and a route-flush timer. The routing-update timer clocks the interval between periodic routing updates. Generally, it is set to 30 seconds, with a small random amount of time added whenever the timer is reset. This is done to help prevent congestion, which could result from all routers simultaneously attempting to update their neighbors. Each routing table entry has a route-timeout timer associated with it. When the route-timeout timer expires, the route is marked invalid but is retained in the table until the route-flush timer expires.

Packet Formats

The following section focuses on the IP RIP and IP RIP 2 packet formats illustrated in Figures 44-1 and 44-2. Each illustration is followed by descriptions of the fields illustrated.

RIP Packet Format

Figure 47-1 illustrates the IP RIP packet format. Figure 47-1 An IP RIP Packet Consists of Nine Fields

The following descriptions summarize the IP RIP packet format fields illustrated in Figure 47-1:

•Command—Indicates whether the packet is a request or a response. The request asks that a router send all or part of its routing table. The response can be an unsolicited regular routing update or a reply to a request. Responses contain routing table entries. Multiple RIP packets are used to convey information from large routing tables.

•Version number—Specifies the RIP version used. This field can signal different potentially incompatible versions.

•Zero—This field is not actually used by RFC 1058 RIP; it was added solely to provide backward compatibility with prestandard varieties of RIP. Its name comes from its defaulted value: zero.

•Address-family identifier (AFI)—Specifies the address family used. RIP is designed to carry routing information for several different protocols. Each entry has an address-family identifier to indicate the type of address being specified. The AFI for IP is 2.

•Address—Specifies the IP address for the entry.

•Metric—Indicates how many internetwork hops (routers) have been traversed in the trip to the destination. This value is between 1 and 15 for a valid route, or 16 for an unreachable route.

RIP 2 Packet Format

The RIP 2 specification (described in RFC 1723) allows more information to be included in RIP packets and provides a simple authentication mechanism that is not supported by RIP. Figure 47-2 shows the IP RIP 2 packet format.

Figure 47-2 An IP RIP 2 Packet Consists of Fields Similar to Those of an IP RIP Packet

The following descriptions summarize the IP RIP 2 packet format fields illustrated in Figure 47-2:

•Command—Indicates whether the packet is a request or a response. The request asks that a router send all or a part of its routing table. The response can be an unsolicited regular routing update or a reply to a request. Responses contain routing table entries. Multiple RIP packets are used to convey information from large routing tables.

•Version—Specifies the RIP version used. In a RIP packet implementing any of the RIP 2 fields or using authentication, this value is set to 2.

•Unused—Has a value set to zero.

•Address-family identifier (AFI)—Specifies the address family used. RIPv2's AFI field functions identically to RFC 1058 RIP's AFI field, with one exception: If the AFI for the first entry in the message is 0xFFFF, the remainder of the entry contains authentication information. Currently, the only authentication type is simple password.

•Route tag—Provides a method for distinguishing between internal routes (learned by RIP) and external routes (learned from other protocols).

•IP address—Specifies the IP address for the entry.

•Subnet mask—Contains the subnet mask for the entry. If this field is zero, no subnet mask has been specified for the entry.

•Next hop—Indicates the IP address of the next hop to which packets for the entry should be forwarded.

•Metric—Indicates how many internetwork hops (routers) have been traversed in the trip to the destination. This value is between 1 and 15 for a valid route, or 16 for an unreachable route.

Summary

Despite RIP's age and the emergence of more sophisticated routing protocols, it is far from obsolete. RIP is mature, stable, widely supported, and easy to configure. Its simplicity is well suited for use in stub networks and in small autonomous systems that do not have enough redundant paths to warrant the overheads of a more sophisticated protocol.

Warriors Orochi 2

2008-11-28T04:06:00.000-08:00

Article at: http://ps2.gamezone.com/gzreviews/r35461.htm

Having moved on to the next-generation of gaming consoles, leave it Koei to continue bringing gamers the same button-mashing action game it has releasing in a seemingly endless cycle. Sure, Dynasty Warriors has branched out into new gaming territory with the likes of Samurai Warriors and now Warriors Orochi but the core mechanics has not changed. The first Warriors Orochi showed us that it’s still fun to rip through hordes of enemies as Japanese or Chinese heroes but Warriors Orochi 2 simply doesn’t do anything to breathe new life into a series that is starting to show its age.

Taking place directly after the first game in the new series, Warriors Orochi 2 finds the Serpent King Orochi bored and in need of testing his might in order to prove to himself that he is a forced to be reckoned with in any timeline. So plucking heroes from different eras (from each series that range from the original Dynasty Warriors to Samurai Warriors 2 Xtreme Legends), he brings them together to pit his armies against legendary heroes that finds themselves questioning their loyalties and forming strange alliances.

Once again, you are given a choice between different kingdoms that range from different dynasty eras of Chinese legends to samurai warriors. It’s still something of a thrill to be in the same battlefield that includes historical figures such as Liu Bei, Cao Cao, Nobunaga Oda and Hanzo Hattori. Story Mode takes you through a number of battles against the Serpent King’s allies and followers such as the devious Da Ji. Of course, you’ll also go through familiar faces that have aligned themselves with Orochi.

All the elements from the last game are back including the character RPG-styled leveling up and you can also upgrade your weapons to dish out more damage against commanding officers on the field. Like the last game in the series, you can also rendezvous with other friendly units on the field to form a complete unit. Say you’re attempting to take down an enemy commander and don’t want to do it alone, well, you can aid a friendly hero like Shingen Takeda on the field and then have him join you to take down the powerful enemy commander.

Having control over three characters also allows you to switch them on the fly to take advantage of their unique abilities and weapon specialties. You can also perform a chain Musou attack when two members of your three-warrior team has a full Musou Gauge and perform an even powerful attack that can wipe out a dozen enemy foot soldiers at once. Once again, the controls are simple enough that even gamers new to the series can easily pick up a controller and start ripping into the enemy without much trouble.

Of course, as I mentioned in the beginning, gamers who have been playing Koei’s hack-and-slash games will find that even with the 90 or so characters in the line up this game feels like every other one in the franchise. No matter what dynasty you pick in Story Mode, the end result is always the same even though the locales are different. Thankfully, other modes such as Survival Mode break up the repetitive and dated cycle of the game’s Story Mode. Survival Mode actually plays like a Survival Mode in most fighting games and this is a fun twist. In this mode, you can pick three characters from any of the available dynasties or any character you might have unlocked while playing Story Mode and battle against a three-man tag team. The more teams you defeat the more points you win.

Making its debut is Dream Mode, a mode that offers a number of interesting scenarios that play out much like the ones in Story Mode. The catch here is that it features characters that would normally wouldn’t be seen together such as the odd pairing of Yoshimoto Imagawa, Xing Cai and Ginchiyo. The situations are actually the most interesting seeing as they include objectives that have you attempting to save a friend or provide a diversion in order to aid another squad as they attempt to breach a castle.

Free Mode is also back as is the game’s two-player VS Mode. VS Mode, once again, contains interesting multiplayer fun such as Tower and Elimination but once again, the four game match types are only played on a single console with only one friend. Once again, online multiplayer is a no-show and that hurts the game’s multiplayer mode plenty seeing as this game would have been a blast to play with more gamers.

On the visual front, the game does not change its visual style either. This is not to say that it’s completely bad seeing as the character models look good in action and during the brief cut scenes but the backgrounds are still an eyesore. The washed out textures and the hazy fog that suddenly disappears just doesn’t belong anymore and the PlayStation 2 certainly could do a lot better than what we see in Warriors Orochi 2. Even the neat effects aren’t able to keep from noticing the awful-looking environments.

The game’s sound fairs a tad better but not by very much. The same heavy rock guitar riffs are back and they play throughout each battle without changing the beat. Of course, there are times in the game (such cut scenes or different game modes) contain some decent tunes that should have replaced the guitar tunes. The voice acting is also slightly better. In past games, the dialogue has been handled poorly but here even the game’s narrator does a passable job.

While some fans of Koei’s button-masher take comfort in its familiar style, it’s hard to ignore the fact that the repetitive action is starting to get dated. We love new characters tossed into the mix and a new game mode as well, but this is not enough to distract us from the truth that the series just isn’t as exciting as it once was when Dynasty Warriors was first introduced. If you missed the first Warriors Orochi game and must have one then this sequel is the one you should buy. Other than that, there’s very little about Warriors Orochi 2 for the PS2 that feels fresh or original.

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Only Character can Walk Thru Walls, not the horse.
RNWE-UFE1-YYV42
CYV2-0960-AZRT7

The normal 5 unit squad of enemies doubles, but 9 have half the health and the l
eader has full heal
DT9G-0KM5-9NXMB
XKK2-VT9W-C3557

With who jump cancellation & frequency limitlessness
U8M4-VH0E-74ZZ9
WYFT-BZ2G-QEWG7
X9D7-ZB1R-HKAB2
GXR8-7TU1-K2VU7
35TZ-BX9J-YURE4

It is to be difficult to fall,
2FX0-0C5K-XRJEK
1Z6H-DZZ0-TREGQ

K.O. Count x32
9W2D-5BFK-C6EKK
EPE7-EUAB-6DXTW

Restriction time 2hrs
CN3C-1M3C-QH1N0
HWC1-QXE2-354J4

Drift speed & jump power x100
1KC4-BEAD-RMRGE
JZBX-M2C5-Q9UJ3
8A8U-2XDR-8YGKX
1QNK-Q7A2-1HRMY

Afterimage
8B86-PZ1U-3HHMK
JYWH-WY85-7NP65

Afterimage (Hanzo type)
R8J5-CJ52-MEPU4
VNWB-KZWU-UZWYV
more codes for NTSC. here.

== Battle codes ==

Infinite Musou
31C1-Q4ME-67G39
01YW-5DYK-FGTAQ

Max Musou
X0D6-D5N1-J7499
00QQ-WGDX-FDQQH

Infinite/Max Energy
2WVQ-F1A8-26XGX
0JYT-YNZ1-N163R

Speed normal
H9E8-8FW8-N8N72
DBD0-9KEQ-4HYEZ

Super Speed
BBC0-WGQ4-QTWM1
EFZM-TU3P-PYK73

Hyper Speed
RZX0-FEMF-0J5KB
BZAY-9VN4-E770D

Ultimate Speed
HA93-RJZT-3MMT7
MPNC-15WC-7Q3WA

normal jump
4CGD-PZC2-QEMJ4
1T0J-7P2U-156GJ

Super jump
3CJE-D0FT-6AKN8
DM3C-TH9N-VW3CH

Hyper Jump
7HFW-QEG3-UQMC1
DQH3-9QUN-T8CUJ

Ultimate Jump
K6VG-D2CJ-XKJAN
CJUA-ECHX-5DEKE

infinite time Defensive x2 (on pickup)
KF4C-1EPF-TYCAF
JXH2-7BCG-D6PMV

Infinity attack x2 (on pickup)
9ZP5-FBH6-41XJ4
RK8M-HW85-YAC48

Musou infinite time (on pickup)
K3JT-7QAB-UCW6F
Z4D7-0D4Z-Y1RJY

Speed infinitely x2 (on pickup)
C2J3-25A3-1KTRD
BF9U-VC0Y-D0UDG

KO 9999
0ZUX-MD0M-1MU3Z
TR5C-ABJ4-R3H8M

Code At : http://www.gamefaqs.com/boards/genmessage.php?board=944760&topic=46490436

Defraggler

2008-11-28T04:03:00.000-08:00

From Piriform, the company that brought you CCleaner and Recuva... they now bring you a file defragmentation tool... Defraggler!

It differs from other defrag tools on the market, by enabling you to quickly and simply defrag the files you want to, without having to process the whole drive. Simply run it, select the file and defragment in seconds. No more struggling with the Windows defragmentation tool!

Defrag Individual Files
Compact and Portable
Vista Support
Locate Files on the Drive
Freeware

And remember like all Piriform products, Defraggler is completely free for both corporate and individual use.

links : http://www.filehippo.com/download_defraggler/

Signs to Know She Loves You

2008-11-20T21:30:00.000-08:00

Given below are some ways to know if she likes you and want to carry on a long-term relation with you:

* If she cares for you and always take interest in your activities then she truly loves you.

* If you come to know from her family and friends that she often brags about you shows her love for you.

* If a girl tries to get closer to you by touching your hands, shoulders or cheeks means she likes you.

* If she keeps staring you when the conversation is on depicts that she likes you and want to say something but is shy of that.

* When a girl blushes on your talks and keep praising you in front of your friends then she loves you.

* When a girl does not respond to the messages or calls given by you it means she is trying to avoid you.

* If she doesn't want to declare it in public or make some excuses when caught by your close friend in public by saying, “ he's my friend”, shows her disinterest in you.

* If she never praises you and keeps counting flaws in you means she's trying to dissolve the relation by taking these flaws as the base.

* A girl is deeply in love with a guy is she accepts his family no matter how they are.

* When she talks to you very nicely after a long time means she is in need of you and is talking to you merely for your company as she has no other solution.

* If she always encourage and motivate you to go ahead with your plans then she is an ideal lover and is sincerely attached with what you want from your life.

* If she wants to spend some time with you and want to help you out in every project or assignment means her love for you.

Persona 3: FES

2008-11-19T21:44:00.000-08:00

Article at : www.brighthub.com/video-games/console/reviews/6009.aspx

Though some two decades into its evolutionary cycle, the traditional role-playing genre has arguably experienced no cataclysmic shifts of redefinition: no meteors of change have made fully extinct the dinosaurs of random encounters, no modifying ice ages have eternally encased the Paleolithic trope of hit points within their glaciers. Fundamentally, what was created in Japan as Dragon Quest in 1986 remains the foundation of most subsequent RPG experiences, Eastern or Western. While Persona 3: FES (an awkward abbreviation of “festival,” not “festoon,” as popularly misconceived) represents by no means a global upheaval in what is elementally understood as the role-playing game, it does herald, in crude cave-painting hieroglyphs, the dawn of style in this often-utilitarian genre.

For a lack of a more evident thematic touchstone in spite of my 40-plus hours with FES, the game’s aggregate message seems to be one of evolution. Just as Persona 3’s presentational finesse – conveyed by way of cel-shaded, anime-esque visuals, polychromatic menus which highlight artwork as much as numerical data, and a soundtrack which melds rap, hip-hop, techno, and ambient foundations to deliver a foreward-thinking yet gameworld-appropriate score the closest kin of which is, bizarrely, Street Fighter 3: Third Strike – evokes progression, so, too, does its plot. The player controls a nameless, silent, history-devoid, high-school attending hero in possession of exceptional spiritual talents (in the game’s most egregious adherence to convention) who, over the course of a year, must, along with his similarly-gifted dorm-mates, wage war with a demonic legion. At the stroke of midnight, each night, the demons (or “shadows,” as they’re known as in-game) transubstantiate all denizens of modern Tokyo, save a few, into coffins(!?) and conduct their diabolic business during the green-hued clutch of non-time known as the “Dark Hour.” Naturally, the game’s heroes are unaffected by this shadowy magic, utilizing instead gun-shaped instruments known as “evokers” to draw out, by shooting themselves in the head, their inherent mystical beings, the eponymous “persona,” and combat the creeping wickedness, all the while venturing to excel in their studies and maintain the social lives of an adolescents not versed in mass-exorcism. And as the main character forms status-affecting bonds with his dorm-mates as well as other students he befriends during this year, so, too, will he level up, create unique persona by way of fusion (as chaperoned by the phallus-nosed occultist named Igor) in the subspace Velvet Room, complete various quests for the succubus demon Elizabeth whose ignorance of modern culture grants her a relatable innocence, and traverse the labyrinth-tower of Tartarus in an effort to locate and obliterate the nexus of the shadows’ devilry. More mundane tasks, such as purchasing items and equipment from a home-shopping channel, playing arcade games, and partaking in a variety of extracurricular activities, like art club and swimming, also contribute to the nameless hero’s development during this alternatingly odd-yet-routine year in the Tokyo of today.

In returning to the aforementioned theme of evolution, this dichotomy of ancient vs. contemporary, as evinced in both Persona 3: FES’s story and gameplay, converges to form an experience familiar yet ultimately progressive. Such contrasts of the old and new clash continuously: the plot is rote while its modern setting is novel (for an RPG, which ritualistically occur in either the fabled past or the hyper-future); the game’s reliance upon dungeon-crawling and level-grinding is customary while its equally-weighted prevalence of social interactions and even dating scenarios lend originality; and even this FES edition of Persona 3 is fixed to dichotomy, as the original game is presented here as “The Journey,” while an entirely new episode, “The Answer,” which is a continuation of the standard game and unique to this disc, is selectable from the title screen. (And perhaps the greatest yet most negligible example of this principle is the fact that the innovative Persona 3: FES is available only on the PS2, an indolent – some would argue dying, or dead – system.) Curiously, given the freedom of choice promoted by Persona 3 and the rampancy of digital Darwinism to be found within, the near-fascist restrictions it imposes are intensified. Gameplay unfolds on a day-to-day basis, and these days are segmented into periods, such as early morning, lunchtime, and late night. During each period only, typically, one set action may take place – the answering of a question in a class, or a social date to the ramen stand with a friend. Consequently, it is often impossible to indulge in social time and purchase items necessary for upcoming combat in the same day, and soon the unending responsibility of pleasing all social contacts yields stress rather than pleasure (also see Grand Theft Auto IV). Combat is possible only at night, and only if all party members, none of which the player controls except the nameless hero, are well-rested. Scripted events based on the time of the year may make combat at certain times unselectable, and in combat party members whose actions may only be programmed generally will sometimes cast spells which have been proven to be ineffective against a particular monster. Indeed, an illogical and oft-infuriating amount of rigidity somewhat hampers the otherwise avant-gardeness of Persona 3, and, in a way, its once-exciting amalgamated gameplay diminishes somewhat into an RPG regimen of a distinct sort.

Exonerations must be allowed, however, considering the game’s ambitions, its visual and aural fluidity, its microcosmic encapsulation of life today, its bravery in forcing the player to consider what relevancy old gods (as represented by the personae, here) assume in present day existence. What must be remembered, amidst all of this, is that even evolution is beholden to cyclicality.

Cheat Codes

#
(M)
66EH-5C5R-PV647
GENQ-PYJ9-4GN61

#
Infinite Cash
02J5-B3HX-PTQ28
8XEV-W2T8-GQNPU

#
Max Cash After Buying An Item
7QHG-RUQC-NB2DN
N1WR-B0EB-Y57GC

#
All Expendable Items Available
8ZAE-NV04-K15YP
E7WQ-HQNN-16DH1

#
Super Persona Modifier Code:
ZW1D-FKMC-BNFT3
KKPD-557F-9HYUY
2HQG-82W1-35CWN
CAWV-HDA5-Q77PE
05YX-0C4G-U3HGX
BUC1-PH9E-8GBWP
YP72-VDJT-D5PW9
7ADG-NWY0-2RGRK
7DRV-TQ4X-X8P4G
5XHF-6G4U-J15YF
GRNZ-BXBY-YU9UK
BWUG-2VCB-3BAM7
G1P5-6MJB-KF1M3
M2J8-CUVH-K86EF
PJM5-WRUY-1FAUB
DMC3-HQDN-URNH1
GT9C-9U89-N5ZDN

With this code on, All empty persona slots will be replaced by a new persona each time you open the persona menu. Dismiss all personas you do not want to keep, go out of the persona menu then select it again for next personas to appear.
#
Main Character Codes:
HYTV-5EAJ-6EUJY

#
Infinite Health
0X54-X6YE-D587P
ATTW-8T6Q-0UGBC
3VFJ-FGGH-44MVC

#
Infinite Health & MP
RCG4-U9NK-Z4G3J
ATTW-8T6Q-0UGBC
3VFJ-FGGH-44MVC
4T17-PDPR-YHYFW

#
Support Character Codes:
7EKU-DVQC-0KM63

#
Infinite Health
HQFJ-36K2-6GBXR
YECY-2FKX-5DMZG
T19C-HPXJ-AGMBZ

#
Infinite MP
T5EK-T7N2-QHX6W
MEWR-6CQV-GYWYH
NJ0X-ZQUR-A02TK

#
Quick Experience Codes:
V3UU-Z0UD-A5BHA

#
100 XP Per Fight
AYD8-KMV6-274DP
N42B-H2P5-9GVM8
4QUK-HF3A-Z0FXV

#
200 XP Per Fight
34QA-RFJB-3AM4Z
N42B-H2P5-9GVM8
M37J-ZK9G-TVPQ5

#
500 XP Per Fight
5UCX-QDM4-D948A
N42B-H2P5-9GVM8
MCGK-B6A3-PXN4J

#
1000 XP Per Fight
42HT-UAAW-UT8VV
N42B-H2P5-9GVM8
H466-DJNE-9D9RU

#
5000 XP Per Fight
V4AH-3BHY-7AEA0
N42B-H2P5-9GVM8
KQM3-4HXC-GTWTR

#
10000 XP Per Fight
XU2T-DQTU-YWN3R
N42B-H2P5-9GVM8
PKM0-TDHV-YR9RR

#
25000 XP Per Fight
88MC-HB4R-2XFH1
N42B-H2P5-9GVM8
KNHV-YBR8-A51H8

#
50000 XP Per Fight
UMYB-WUKG-9QHGP
N42B-H2P5-9GVM8
N54R-PEMM-X2DH9

#
100000 XP Per Fight
6AGF-P62K-4T3F3
U1DQ-QBT3-0VMTF
7VDE-9B44-GQYR1

#
500000 XP Per Fight
U09B-CJ2J-RY1YJ
522N-XKR1-KXRTZ
QMXW-U9G6-T7VRU

#
Max XP After A Fight
4A4X-WZ3M-8Y3KJ
EB18-H3F6-E0DFF
YV1J-7CHH-QPZ5Q

Cheat codes by: http://uk.codejunkies.com/search/codes/Shin-Megami-Tensei--Persona-3_Action-Replay-Max_13634128-13___.aspx

AMD vs. Intel: Updated Platforms Set Stage for 2009

2008-11-17T19:41:00.000-08:00

Articles On: http://blogs.pcmag.com/miller/2008/11/amd_vs_intel_updated_platforms.php

So now that AMD has updated its product roadmap, I thought it would be interesting to compare its plans against Intel's, and see where the two stack up in terms of the systems you're likely to see in the market in 2009.

For the high-end desktop or enthusiast sector, Intel will formally announced its X58 "Tylersburg" platform on Monday, featuring its first Core i7 processor, using the "Nehalem" processor design, although some benchmarks are already out. This is a four-core design, with 8 megabytes of level 3 cache and hyperthreading built in, so it can run 8 simultaneous threads. Like most of Intel's current Core 2 Quad and Duo processors, this is based on a 45nm processor. This design is Intel's first with an integrated memory controller and its new QuickPath Interconnect.
AMD%20Client%20Roadmap%20-%20Fall%2008.jpg

AMD's counter to that, launching at CES in January will be its Dragon Platform, including the R700 chipset and its new Phenom II X4 processor, known as "Deneb" processor. This will be AMD's first desktop 45nm processor, and will have 4 cores and 8 MB of cache. AMD has not announced the speeds for this chip yet, but its "Shanghai" server equivalent, was announced yesterday at speeds from 2.3 to 2.7 GHz.

Intel%20Roadmap%20-%20Fall%2008.jpg

I'm not going to judge performance until I have real systems, but almost everyone seems to be assuming Intel will keep the raw performance crown in this market throughout the year. The early Core i7 benchmarks look terrific, and the platform supports both ATI and nVidia discrete graphics. Even AMD seems to acknowledge this, talking about how it was focusing more on the mainstream and value segments.

In mainstream desktops, Intel is currently shipping its Core 2 Duo and Core 2 Quad processors, based on the "Penryn" design; later in the year, it plans to introduce versions based on the new core design. This will include the Piketon (business) and Kings Creek (consumer) platforms, based on the Lynnfield (4-core) and Havendale (2-core) processors. AMD is currently shipping Perseus (business) and Cartwheel (consumer) platforms for its Phenom X4 and X3 processors; it now plans to update these platforms in the second half of 2009 with Kodiak (for business) and Pisces (for consumers). These platforms will include a new 880 chipset, and a new processor in called Propus with 4 cores and 2 MB of cache.

Intel's current notebook platform is called Montevina, with both quad-core and dual-core versions of the Core 2 architecutre. In the middle of 2009, these will be updated with the Capella platform, with Clarksdale (4-core) and Auburndale (2-core) chips. AMD's current notebook platform is Puma and is primarily going to be replaced by Tigris next year, with updated integrated graphics and a dual-core processor called Caspian (a quad-core chip called Champlain is slated for 2010, but I wouldn't be surprised to see small volumes next year if other quad-core notebooks are successful.)

These mainstream areas - for both desktops and notebooks are where the real competition between the two companies will be. Expect Intel to continue to emphasize CPU performance, while AMD to talk about "balanced systems" and emphasize how its integrated graphics are superior to those Intel has. And of course, the two companies will compete on price as well.

There's a bit of a difference in strategies for ultraportable and mini-notebook computers. Intel offers low-power versions of its Core 2 processors for the ultraportable market, with the Atom processor aimed at "netbooks". AMD yesterday announced plans for both the "Congo" platform with a dual-core Conesus CPU and the R700 chip set for the ultraportable consumer market along with "Yukon" with a single-core Huron CPU and a less powerful chip set. Note that these are not directly aimed at Atom; they are higher-performance, higher-power chips that wouldn't fit into the mobile internet devices Atom originally targeted. This could be a very interesting showdown, simply because the companies have taken such different approaches.

So those are the new roadmaps for 2009. Typically, these always change somewhat, with minor variations to the processors and more details on chipsets, speeds etc. But these will set the chip competition for next year - anyway you look at it, we should be seeing systems that are somewhat faster, less power hungry, and more specifically designed for mobile use.

We've got to Save Our Planet Earth!

2008-11-15T22:25:00.000-08:00

Oh, No!: Bad Facts about our earth

If you throw away 2 aluminum cans, you waste more energy than 1,000,000,000 (one billion) of the world's poorest people use a day.
Making a new can from scratch uses the uses the energy equal to half a can of gasoline.
About one third of what an average American throws out is packaging.
More than 1,000,000,000 (one billion) trees are used to make disposable diapers every year.
In one minute, 50 acres of rainforest are destroyed.
Some rain has a pH of 3 or 4. (which is pretty acidic, considering 7 is neutral, not acidic, and battery acid has a pH of 1). Some fish, such as lake trout and smallmouth bass, have trouble reproducing at a pH of 6, which is only slightly acidic. Some clams and snails can't survive at all. Most crayfish are dead at a pH of 5. You can see how bad this is for the environment.
On average, a person in the US uses energy two times more than a person in Japan or West Germany does, and 50 times more than a person in India.
About 90% of the energy used in lighting a standard (incandescent) light bulb is lost as heat.
Air conditioning uses 10 times more energy than a fan, therefore, it creates 10 times the pollutants.
It takes half the output of the Alaskan pipeline to heat the air that escapes from all the homes in the US during a year.
Cars and pick-up trucks are responsible for about 20% of the carbon dioxide released into the air.
There are about 500 million automobiles on the planet, burning an average of 2 gallons of fuel a day. Each gallon releases 20 pounds of carbon dioxide into the air.
About 80% of our trash goes to landfills, 10% is incinerated, and 10% is recycled.
Since there is little oxygen underground, where we bury our garbage, to help bacteria eat the garbage, almost nothing happens to it. Scientists have dug into landfills and found ears of corn still intact after 20 years, and newspapers still readable after 30.
The average American makes about 3.5 pounds of trash a day.
In a year, the average American uses as much wood in the form of paper as the average resident of the developing world burns as fuel.

26 things we can do to help:

Turn off lights.
Turn off other electric things, like TVs, stereos, and radios when not in use.
Use rechargable batteries.
Do things manually instead of electrically, like open cans by hand.
Use fans instead of air conditioners.
In winter, wear a sweater instead of turning up your thermostat.
Insulate your home so you won't be cold in winter.
Use less hot water.
Whenever possible, use a bus or subway, or ride your bike or walk.
Try to buy organic fruits and vegetables if you're concerned about pesticides. (Organic food is grown without man-made fertilizers and/or pesticides).
Don't waste products made from forest materials.
Use recycled paper and/or recycle it. Reuse old papers.
Don't buy products that may have been made at the expense of the rainforest.
Support products that are harvested from the rainforest but have not cut down trees to get it.
Plant trees, espessially if you have cut one down.
Get other people to help you in your cause. Make and/or join an organization.
Avoid products that are used once, then thrown away.
Buy products with little or no packaging.
Encourage your grocery store sell environmentally friendly cloth bags for people to use when they shop, or bring your own.
REDUCE, REUSE, & RECYCLE.
Compost.
Buy recycled products.
Don't buy pets taken from the wild.
If you have a good zoo nearby, (if the animals are healthy and the zoo takes care of them), support it! Espessially if they help breed endangered animals.
Don't buy products if animals were killed to make it.
Cut up your six-pack rings before throwing them out.

How to Earn Money Using Adsense

2008-11-14T21:14:00.000-08:00

Steps

Don't put ads on empty pages.
Build a skeleton set of pages that have no content, just titles and some meta tags. Ads could be displayed on them; although all you see are public service ads at first, but the very act of displaying ads on a page causes the AdSense web crawler to quickly fetch that page for analysis. A page with good content will thus begin showing relevant paying ads fairly quickly.
If you don't have any content, though, Google will have to guess as what your page is about. It may guess wrong, and so the ads that it displays may not be relevant. You'll have to wait until Google re-crawls the site for the ads to correct themselves. Here is what Google had to say when I asked them about how often the AdSense crawler updates a site:
- Thank you for taking the time to update your site. New ads will start appearing on your site the next time our crawler re-indexes your site. Unfortunately at this time, we are unable to control how often our crawlers index the content on your site.
- Crawling is done automatically by our bots. When new pages are added to your website or introduced to the AdSense program, our crawlers will usually get to them within 30 minutes. If you make changes to a page, however, it may take up to 2 or 3 weeks before the changes are reflected in our index. Until we are able to crawl your web pages, you may notice public service ads, for which you will not receive any earnings.
It's better to flesh out the page before you start displaying ads on it.
Don't be afraid to ask questions.
If you're wondering about something, don't be afraid to ask Google. They are very good at responding within a working day. There are two email addresses to use, depending on the type of question:
- Please feel free to email us at adsense-tech@google.com if you have additional technical questions or concerns. For general program or account questions, please email adsense-support@google.com.
Their responses are always very polite, and they appreciate getting problem reports and suggestions.
Avoid non-English characters on English pages.
- This one is a bug at this time.
- Normally, this wouldn't be an issue, but on some pages the presence of the accented characters is enough to cause AdSense to display non-relevant ads in French. This happens whether the browser indicates a preference for French or not. When this was reported to Google, this is the response:
  - Thank you for bringing this issue to our attention. We are currently working as quickly as we can to address this problem. As soon as we have more information for you, we will email you again. We appreciate your patience.
  - Sincerely,
  - The Google Team
- Until this is resolved, it is a good idea to strip out all accents except on the pages that are actually in French.
Check your keyword density.
Although Google doesn't release exact details as to how they determine the ads to serve on a given page, they do tell us that it's the text content of the page that matters, not the meta tags. Before serving ads on a page, then, you might want to check its keyword density. A good, free tool for doing this is found here

Tips

Do not click your ads. If Google catches you, they have the right and will close your account and retain any earnings you might have.
To get lots of visitors you need an unique idea for your site. You can get help by searching the Internet with keywords "website ideas".
Using a site like http://www.flixya.com, is a quick and easy method to driving traffic, which will help. As an individual, it may take time to build, advertise and see revenue from a site with little content or activity. Revenue sharing websites like Flixya (which offers 100% revenue to every member) is the best way to get started.

2008 Internet Service Provider Product Comparisons

2008-11-14T20:59:00.000-08:00

Why Internet Service Providers?

In many homes, a computer with an Internet connection has become as common as a telephone or television—in fact, many would give up their telephone or TV before they would give up their Internet connection.

The World Wide Web is a source of unlimited information and possibilities: students use the Internet for their studies, practically anything can be purchased online (it's particularly good for specialty items), the Internet is a great source for news, entertainment, and people all over the world can communicate instantly online.

There are various types of Internet connections, including dial-up, cable, wireless, DSL and satellite, and hundreds of Internet providers. Each provider has a service area, offers certain types of connections and provides customers with other benefits, such as email, security against viruses and other harmful programs, webpage space and more—finding the ISP that fits your needs and is available in your area can be a daunting task

In this site, you'll find articles about ISPs and comprehensive reviews on Internet service providers that will help you make an informed decision on which ISP fits your needs. At TopTenREVIEWS, we do the research so you don't have to.™

What to Look for in Internet Service Providers

Ideal Internet providers offer a number of different connections, including dial-up, DSL, cable and satellite, and they offer these services to a large number of people. The ISP should provide ample protection to customers using firewalls, parental controls and virus and spyware protection. Convenient, helpful customer service is a must.

Below are the criteria TopTenREVIEWS used to evaluate Internet service providers.

Feature Set – Internet service providers (ISPs) should include certain elements as a basic part of their service, including virus and spyware protection, firewalls, parental controls, email accounts, webpage space and more.

Service Area – Internet service providers that offer service to a large region ranked higher in our reviews, since larger ISPs can usually offer more for less. The ISP website should supply tools that show if their service is available in your area.

Connection Speeds – Internet providers that offer a choice of bandwidths, or data transfer space (the greater the bandwidth, the greater the speed of your connection) allow you more flexibility when choosing an Internet service plan.

Customer Service/Support – The ISP should have excellent customer service, including a FAQs page, phone support, a customer support email address and live chat. The ISP should respond to customer questions promptly.

Internet service providers open the windows of media, education, entertainment, information, communication and so much more. So whether you use the Internet for business, pleasure or school, and no matter your budget or surfing pace, you'll find the ISP that suits your style right here.

links

Insurance Agent: Insurance Company & Tips Insurance

2008-11-14T20:47:00.000-08:00

Business insurance is vital for being certain that your business is protected against unforeseen disasters. Without insurance, a successful business built with hard work and toil could be easily wiped out destroy the businessman's finances completely. However, with insurance you are guaranteed a fresh start.

The first step towards getting the right business insurance is to find the right business insurance agent. A good business insurance agent will understand your business needs and will make sure you go in for the right kind of insurance that suits your business.

Some small businesses make the mistake of hiring personal line agents, who lack the experience and the knowledge to get the appropriate insurance package. Be certain the insurance agent has commercial experience , expertise, and access to multiple insurance agencies making it possible to get the best coverage at the best price possible.
Tips to Find the Right One

1.Ask acquaintances, friends and relatives in the same line of business to recommend an agent.

2.Ask your personal line agent to recommend a good business insurance agent.

3.Get business associates to recommend a good agent.

4.Get a list of business insurance agents from the yellow pages, meet prospective agents, and select the best agent of them all.

5.Do a search on the Internet.

6.View profiles of insurance agents operating in your area.

7.If your business operates in more than one state, make sure your insurance agent does too.

8.Check if there are complaints filed against the agent or the company he represents with the Better Business Bureau. The insurance agent you select should be knowledgeable and able to convince you the agent is reliable and understands your company's insurance needs. The company the agent represents should also be trust worthy and reputable.

These are just a few tips on how to find the right business insurance agent. Once you have chosen a qualified and capable agent, make sure you choose the best coverage possible at the best price available.

It will be good if the agent has prior experience in dealing with a company similar to yours. Make sure you understand how your premium is determined and go for package policies since they are cheaper. Consult a few people and then decide which policy is right for you, do not blindly buy a policy the agent suggests unless it is the right one for you. Choose an independent agent as this agent has a variety of policies to offer rather than a captive agent. Be sure to make an informed decision. Additional Help There are a few firms that offer their services and products to new business owners making the task of running a business easier.

Author
David Gass

TCP/IP

2008-11-11T20:48:00.000-08:00

ntroduction to TCP/IP

Summary: TCP and IP were developed by a Department of Defense (DOD) research project to connect a number different networks designed by different vendors into a network of networks (the "Internet"). It was initially successful because it delivered a few basic services that everyone needs (file transfer, electronic mail, remote logon) across a very large number of client and server systems. Several computers in a small department can use TCP/IP (along with other protocols) on a single LAN. The IP component provides routing from the department to the enterprise network, then to regional networks, and finally to the global Internet. On the battlefield a communications network will sustain damage, so the DOD designed TCP/IP to be robust and automatically recover from any node or phone line failure. This design allows the construction of very large networks with less central management. However, because of the automatic recovery, network problems can go undiagnosed and uncorrected for long periods of time.

As with all other communications protocol, TCP/IP is composed of layers:

* IP - is responsible for moving packet of data from node to node. IP forwards each packet based on a four byte destination address (the IP number). The Internet authorities assign ranges of numbers to different organizations. The organizations assign groups of their numbers to departments. IP operates on gateway machines that move data from department to organization to region and then around the world.
* TCP - is responsible for verifying the correct delivery of data from client to server. Data can be lost in the intermediate network. TCP adds support to detect errors or lost data and to trigger retransmission until the data is correctly and completely received.
* Sockets - is a name given to the package of subroutines that provide access to TCP/IP on most systems.

Network of Lowest Bidders

The Army puts out a bid on a computer and DEC wins the bid. The Air Force puts out a bid and IBM wins. The Navy bid is won by Unisys. Then the President decides to invade Grenada and the armed forces discover that their computers cannot talk to each other. The DOD must build a "network" out of systems each of which, by law, was delivered by the lowest bidder on a single contract.

ipdept.gif

The Internet Protocol was developed to create a Network of Networks (the "Internet"). Individual machines are first connected to a LAN (Ethernet or Token Ring). TCP/IP shares the LAN with other uses (a Novell file server, Windows for Workgroups peer systems). One device provides the TCP/IP connection between the LAN and the rest of the world.

To insure that all types of systems from all vendors can communicate, TCP/IP is absolutely standardized on the LAN. However, larger networks based on long distances and phone lines are more volatile. In the US, many large corporations would wish to reuse large internal networks based on IBM's SNA. In Europe, the national phone companies traditionally standardize on X.25. However, the sudden explosion of high speed microprocessors, fiber optics, and digital phone systems has created a burst of new options: ISDN, frame relay, FDDI, Asynchronous Transfer Mode (ATM). New technologies arise and become obsolete within a few years. With cable TV and phone companies competing to build the National Information Superhighway, no single standard can govern citywide, nationwide, or worldwide communications.

The original design of TCP/IP as a Network of Networks fits nicely within the current technological uncertainty. TCP/IP data can be sent across a LAN, or it can be carried within an internal corporate SNA network, or it can piggyback on the cable TV service. Furthermore, machines connected to any of these networks can communicate to any other network through gateways supplied by the network vendor.
Addresses

Each technology has its own convention for transmitting messages between two machines within the same network. On a LAN, messages are sent between machines by supplying the six byte unique identifier (the "MAC" address). In an SNA network, every machine has Logical Units with their own network address. DECNET, Appletalk, and Novell IPX all have a scheme for assigning numbers to each local network and to each workstation attached to the network.

On top of these local or vendor specific network addresses, TCP/IP assigns a unique number to every workstation in the world. This "IP number" is a four byte value that, by convention, is expressed by converting each byte into a decimal number (0 to 255) and separating the bytes with a period. For example, the PC Lube and Tune server is 130.132.59.234.

An organization begins by sending electronic mail to Hostmaster@INTERNIC.NET requesting assignment of a network number. It is still possible for almost anyone to get assignment of a number for a small "Class C" network in which the first three bytes identify the network and the last byte identifies the individual computer. The author followed this procedure and was assigned the numbers 192.35.91.* for a network of computers at his house. Larger organizations can get a "Class B" network where the first two bytes identify the network and the last two bytes identify each of up to 64 thousand individual workstations. Yale's Class B network is 130.132, so all computers with IP address 130.132.*.* are connected through Yale.

The organization then connects to the Internet through one of a dozen regional or specialized network suppliers. The network vendor is given the subscriber network number and adds it to the routing configuration in its own machines and those of the other major network suppliers.

There is no mathematical formula that translates the numbers 192.35.91 or 130.132 into "Yale University" or "New Haven, CT." The machines that manage large regional networks or the central Internet routers managed by the National Science Foundation can only locate these networks by looking each network number up in a table. There are potentially thousands of Class B networks, and millions of Class C networks, but computer memory costs are low, so the tables are reasonable. Customers that connect to the Internet, even customers as large as IBM, do not need to maintain any information on other networks. They send all external data to the regional carrier to which they subscribe, and the regional carrier maintains the tables and does the appropriate routing.

New Haven is in a border state, split 50-50 between the Yankees and the Red Sox. In this spirit, Yale recently switched its connection from the Middle Atlantic regional network to the New England carrier. When the switch occurred, tables in the other regional areas and in the national spine had to be updated, so that traffic for 130.132 was routed through Boston instead of New Jersey. The large network carriers handle the paperwork and can perform such a switch given sufficient notice. During a conversion period, the university was connected to both networks so that messages could arrive through either path.

Need to Know

There are three levels of TCP/IP knowledge. Those who administer a regional or national network must design a system of long distance phone lines, dedicated routing devices, and very large configuration files. They must know the IP numbers and physical locations of thousands of subscriber networks. They must also have a formal network monitor strategy to detect problems and respond quickly.

Each large company or university that subscribes to the Internet must have an intermediate level of network organization and expertise. A half dozen routers might be configured to connect several dozen departmental LANs in several buildings. All traffic outside the organization would typically be routed to a single connection to a regional network provider.

However, the end user can install TCP/IP on a personal computer without any knowledge of either the corporate or regional network. Three pieces of information are required:

1. The IP address assigned to this personal computer
2. The part of the IP address (the subnet mask) that distinguishes other machines on the same LAN (messages can be sent to them directly) from machines in other departments or elsewhere in the world (which are sent to a router machine)
3. The IP address of the router machine that connects this LAN to the rest of the world.

In the case of the PCLT server, the IP address is 130.132.59.234. Since the first three bytes designate this department, a "subnet mask" is defined as 255.255.255.0 (255 is the largest byte value and represents the number with all bits turned on). It is a Yale convention (which we recommend to everyone) that the router for each department have station number 1 within the department network. Thus the PCLT router is 130.132.59.1. Thus the PCLT server is configured with the values:

* My IP address: 130.132.59.234
* Subnet mask: 255.255.255.0
* Default router: 130.132.59.1

The subnet mask tells the server that any other machine with an IP address beginning 130.132.59.* is on the same department LAN, so messages are sent to it directly. Any IP address beginning with a different value is accessed indirectly by sending the message through the router at 130.132.59.1 (which is on the departmental LAN).

Network Address Translation

2008-11-11T20:40:00.000-08:00

Overview

In the mid-1990's NAT became a popular tool for alleviating the IPv4 address shortage. NAT has proven particularly popular in countries that (for historical reasons) had fewer address space blocks allocated per capita.[citation needed] than, for example, the United States. It has become a standard, indispensable feature in routers for home and small-office Internet connections.

Most systems using NAT do so in order to enable multiple hosts on a private network to access the Internet using a single public IP address (see gateway). However, NAT breaks the originally envisioned model of IP end-to-end connectivity across the Internet and introduces complications in communication between hosts and has performance impacts.

NAT obscures an internal network's structure: all traffic appears to outside parties as if it originates from the gateway machine.

It has been argued that the wide adoption of IPv6 would make NAT unnecessary, as NAT is a method of handling the shortage of the IPv4 address space.[citation needed]

Network address translation involves re-writing the source and/or destination IP addresses and usually also the TCP/UDP port numbers of IP packets as they pass through the NAT. Checksums (both IP and TCP/UDP) must also be rewritten to take account of the changes.

In a typical configuration, a local network uses one of the designated "private" IP address subnets (the RFC 1918 Private Network Addresses are 192.168.x.x, 172.16.x.x through 172.31.x.x, and 10.x.x.x (or using CIDR notation, 192.168/16, 172.16/12, and 10/8), and a router on that network has a private address (such as 192.168.0.1) in that address space. The router is also connected to the Internet with a single "public" address (known as "overloaded" NAT) or multiple "public" addresses assigned by an ISP. As traffic passes from the local network to the Internet, the source address in each packet is translated on the fly from the private addresses to the public address(es). The router tracks basic data about each active connection (particularly the destination address and port). When a reply returns to the router, it uses the connection tracking data it stored during the outbound phase to determine where on the internal network to forward the reply; the TCP or UDP client port numbers are used to demultiplex the packets in the case of overloaded NAT, or IP address and port number when multiple public addresses are available, on packet return. To a system on the Internet, the router itself appears to be the source/destination for this traffic.

[edit] Basic NAT and PAT

There are two levels of network address translation.

* Basic NAT. This involves IP address translation only, not port mapping.
* PAT (Port Address Translation). Also called simply "NAT" or "Network Address Port Translation, NAPT". This involves the translation of both IP addresses and port numbers.

All internet packets have a source IP address and a destination IP address. Both or either of the source and destination addresses may be translated.

Some internet packets do not have port numbers. For example, ICMP packets have no port numbers. However, the vast bulk of internet traffic is TCP and UDP packets, which do have port numbers. Packets which do have port numbers have both a source port number and a destination port number. Both or either of the source and destination ports may be translated.

NAT which involves translation of the source IP address and/or source port is called source NAT or SNAT. This re-writes the IP address and/or port number of the computer which originated the packet.

NAT which involves translation of the destination IP address and/or destination port number is called destination NAT or DNAT. This re-writes the IP address and/or port number corresponding to the destination computer.

SNAT and DNAT may be applied simultaneously to internet packets.

NOTE: 'PAT', as it is referred to here, is referred to by Cisco as NAT 'overloading', as described in this Howstuffworks article, provided to Howstuffworks by Cisco: http://computer.howstuffworks.com/nat3.htm

[edit] Different types of NAT

Network address translation is implemented in a variety of schemes of translating addresses and port numbers, each affecting application communication protocols differently. Some application protocols that use IP address information need to determine the external address which is used for masquerading, and, furthermore, often need to examine and categorize the type of mapping used in a given NAT device. For this purpose, the Simple traversal of UDP over NATs (STUN) protocol was developed. It classified NAT implementation as Full cone NAT, restricted cone NAT, port restricted cone NAT or symmetric NAT.[1][2] and proposed a methodology for testing a device accordingly. However, these procedures have since been deprecated from standards status, as the methods have proven faulty and inadequate to correctly assess many devices. New methods bave been standardized in RFC 5389 (2008) and the STUN acronym now represents the new title of the specification: Session Traversal Utilities for NAT.

source: http://en.wikipedia.org/wiki/Network_address_translation