Computer Networks ppt's ref:Tanenbaum

Introduction

chapter2 The Physical Layer

chapter3 The Data Link Layer

chapter4 The Medium Access Control Sublayer

chapter5 Network layer

chapter6 the transport layer


coming soon........

chapter7 the application layer

chapter8 newtwork security

10 Things that drive Google Philosophy

According to Larry page “The perfect search engine,” would understand exactly what you mean and give back exactly what you want. Mentioned below are the top principles that guide Google’s action :



1. Focus on the user and all else will follow.






2. It’s best to do one thing really, really well.






3. Fast is better than slow.






4. Democracy on the web works.






5. You don’t need to be at your desk to need an answer.






6. You can make money without doing evil.






7. There’s always more information out there.






8. The need for information crosses all borders.






9. You can be serious without a suit.






10. Great just isn’t good enough.

the first googl page-beta version which is registered in 2000

link :

http://web.archive.org/web/19990125084553/alpha.google.com/

_______________________________________________________________

31 interesting facts about google

We all use Google in some way or the other. The way Google has evolved is a story worth telling. Here are some of the interesting facts about Google :

1. The name ‘Google’ was an accident. It was the result of a spelling mistake made by the original founders who thought they were going for ‘Googol’. The domain name “Googol.com” was already taken by the time Google was founded.



2. The domain Google.com was registered on 15 September 1997.

3. The first operations of Google was started in this garage

4. Google (aka Googol) is a mathematical term which means “1 followed by hundred Zeros”. The term ‘Googol’ was coined by Milton Sirotta, nephew of American mathematician Edward Kasne.



5. Google receives daily search requests from all over the world, including Antarctica.



4. Google’s Homepage has 42 validation errors. Check Google Validation

http://validator.w3.org/check?uri=http%3A%2F%2Fwww.google.com



5. Google’s homepage can be accessed in 88 languages including Urdu and Latin.



6. Every day the Google servers receives about a billion search requests . 20 to 25% of Google queries have never been searched before.




7. The main reason why the Google homepage is so simple is because the founders didn’t knew HTML. The submit button was included much later and hitting the return key was the only way to get the search results.



8. The “I am feeling lucky” button is almost never used by the end user. However it was found that removing the button would reduce the Google experience.




9. In the early days of testing Google employees noted people just sitting and looking at the screen. After a minute the tester asked “What are you waiting for ?”. To this the users replied “We are waiting for the page to load”.



To solve this issue the copyright message was added which acted as an end of the page marker.



10. Google has the largest network of translators in the world.



11. All Google employees are encouraged to use 20% of their time working in their own projects. Google news and Orkut are two big examples that grew from this working model.



12. Google consists of over 450,000 servers, racked up in clusters located in data centers around the world.




13. Google started in January, 1996 as a research project at Stanford University, by Ph.D. candidates Larry Page and Sergey Brin when they were 24 years old and 23 years old respectively.The original google project was named backrub.




14. When Google started it indexed 25,000 web pages. Today Google indexes billions of web pages and each time it grows by 10-25%.



15. According to Google “As the web grows search becomes more and more important”. It acts like a library , the bigger the library the more important is the index.




16. The pagerank algorithm uses more than 200 attributes to determine the rank of a given webpage.




17. Google has the largest corporate solar panel installation in the US.



18. The biggest break in search came when Google introduced their improved spell checker seen as “Did you mean ? ”.This feature doubled their traffic and soon the developers discovered that the ideal placement was at the bottom of the search results.




19. Every now and then Google makes small changes and test them with a given set of users. The users aren’t told of this. They are presented with a new interface and the testers observe how the users react to it.



20. Google believe in 20 % – 5% philosophy. According to this, if at least 20% of the users use a feature then it will be included. To make it to the advanced search preferences, at least 5 % of the users need to use a particular feature.





21. In the results found in user testing and design, Google testers found that only a small number of people are typical of the larger user base. Hence,Google labs was born and it monitors how people use each and every service.



22. Gmail – Free email from Google was used internally for nearly 2 years by Google employees before it was launched for public use. The engineers discovered that there are typically 6 types of email users and Gmail was made to satisfy the needs of them.



23. Google’s index of web pages is the largest in the world, comprising of 8 billion web pages. Google searches this immense collection of web pages often in less than half a second.



24. They listen to feedback actively. Emailing Google isn’t emailing a black hole.



25. Google’s first April fool prank went live on April 1st,2000 and was coined “MentalPlex” – Google’s ability to read your mind.

Some thought the announcement of Gmail in 2004 around April Fool’s Day was a joke. (Thanks Mani Karthik)



26. Google Groups comprises of more than 845 million Usenet messages, which is the world’s largest collection of messages or the equivalent of more than a terabyte of human conversation.



27.In a 2006 report of the world’s richest people, Forbes reported that Sergey Brin was #26 with a net worth of $12.9 billion, and Larry Page was #27 with a net worth of $12.8 billion



28. There isn’t any restriction for proper dress code in the Google office. This may include pajamas and even super hero costumes.

29. Tom Vendetta is the youngest google employee ever hired. He was hired by Google when he was 15 years old. Vendetta used to fool his friends by sending fake press releases and news. Vendetta was employed to know the know-how of the teen and to implement them in Gmail security flaws.



30. The first employee that google hired is Craig Silverstein.

31.The first human being named after Google is Oliver google kai. He was born on September 12th 2005 and his parents named him because they wanted Oliver to have as many friends as google has.

11 Web Sites Every Student Should Know

The following is a look at some of the most comprehensive and reliable educational Web sites a student can bookmark and use to research school projects and homework assignments...


MSN Encarta
The free MSN Encarta site features more than 4,500 articles pooled from Microsoft Encarta and comes with dictionaries, maps, fast facts, interactive quizzes, handy homework tools, and more.


Refdesk
Since 1995, Refdesk.com, which stands for "reference desk," has served as a one-click springboard to many of the Web's top dictionaries, encyclopedias, calculators, atlases, news headlines, and search engines. The site also includes a handy "homework helper" section that provides help in all subjects to students in every grade.


HowStuffWorksEver wanted to know why earthquakes happen? How CD burners work? What the sun is made of? These questions, and a large amount of others related to computers/electronics, automobiles, science, entertainment, and people, are all answered at this award-winning Web site. Simply type a query into the search window or peruse the topics by category. Extras include free newsletters, surveys, and printable versions of all answers.




Canada's SchoolNet
Established by the Canadian government, SchoolNet provides English or French links to other educational sites and learning resources. The "@SchoolNet Today" section serves as a handy news source covering the latest educational material, information, Web sites, projects, and contests.


Download.com
Consider Download.com the ultimate file repository that links to literally tens of thousands of downloadable free or shareware programs. This includes utilities for Windows, Macintosh, and Linux, Internet tools, desktop dictionaries and language translators, Pocket PC and Palm applications, and of course, computer games. Visitors can search by typing in a keyword or by perusing the many sections.




Novelguide.com
The Web's answer to those black- and yellow-striped Cliff Notes is Novelguide.com, a reliable and free source for literary analysis of classic and contemporary books such as Mark Twain's Huckleberry Finn and Fyodor Dostoyevsky's Notes from the Underground. The site offers character profiles, metaphor and theme analysis, and author biographies.




Math.com
This site provides help in a number of mathematics-related subjects, including basic grade-school math, calculus, algebra, geometry, trigonometry, and statistics. Practice exercises are automatically graded, plus this free site also features a glossary, calculators, homework tips, math games, and lesson plans for teachers.




Wolfram Mathworld
With more than 12,600 entries one of the most extensive mathematics resource.




FreeTranslation
Sprechen Sie Deutsch? Perfect for language studies, this handy Web site automatically converts text from one language into another, such as English to Simplified Chinese or French to English. Simply type and paste up to 10,000 characters (about 1,800 words) into the search window and then select the desired language. Alternatively, you can cut and paste a Web URL to convert the entire site.




Shakespeare Online
This Web site can be filed in the "where was this when I was a kid?" category. On the aptly named Shakespeare Online site, visitors can read every play or poem from the world's most celebrated writer and, more importantly, make some sense of his works with free analysis and famous quotes.




Science Made Simple
Science classes including the ubiquitous science project aren't as easy for some to grasp as for others. At Science Made Simple, kids of all ages can get detailed answers to many of science's questions, read current news articles related to science, get ideas on school projects, and take advantage of unit conversion tables. Users can also find out if their school's textbooks pass the test. 




I think all these websites may useful in many ways....! 

ALL THE BEST