Web Fundamentals
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The document discusses various topics related to the internet and web fundamentals: - The internet is a global network of interconnected smaller networks owned by no single entity, while the web refers specifically to the collection of hyperlinked documents accessible via HTTP. - HTTP is the application layer protocol for transferring data on the web. Other topics discussed include DNS, cookies, sessions, forms, error codes, and common web/application server architectures. - Questions are also addressed regarding URLs, domains, and the differences between IP addresses and domain names in web requests.
Web Fundamentals
- 1. Web Fundamentals 4 th September 2007 WWW, Internet, and other weird stuff
- 2. This is not a presentation But more of a Discussion Maximum questions Maximum answers (if possible) You are allowed to sleep You will get a copy of these slides But slides are less important. Exercises will be there
- 3. What is Internet? Internet is a global network of smaller networks. Internet is the largest network. It is owned by NOBODY Smaller network: 1-1000 computers Satellites, Submarine Optical cables Backbone The biggest name is Cisco
- 4. What is (the) Web? You mean World Wide Web? Collection of interlinked hypertext documents. That means Hyperlinked documents Hyperlinks? URL
- 5. HTTP? HTTP is an application level protocol for transferring data through WWW. Hyper Text Transfer Protocol HTTP 0.9 / 1.0 / 1.1 / 1.2 HTTPS (S for Secure) HTML – Header, content. They say HTTP is stateless.
- 6. DNS DNS is like post office Some post offices will be knowing some addresses DNS servers will have addresses like this www.google.com => 64.67.33.200 Multiple Name servers for reliability
- 7. Domain Name Netkode.com Mail.netkode.net Abc.mail.netkode.net http://mail.netkode.net/ http://mail.netkode.net:80/ http://mail.netkode.net:80/inbox/index.jsp Port
- 8. A simple web request Browser Name Server Internet Web Server IIS, Apache, Lighttpd etc. BIND, PowerDNS, djbdns HTTP Response DNS Lookup http://bookmarks.rediff.com/recent/ bookmarks.rediff.com => 210.210.93.86
- 9. Cookies Comes in different flavors Through HTTP Headers Persistent Cookie Session Cookie Secure Cookie HTTP Only Cookie 3 rd Party Cookie
- 10. How Cookies work? 2) Response from Web server 3) 2 nd request from browser 1) Request from Browser GET /index.html HTTP/1.1 Host: bookmarks.rediff.com HTTP/1.1 200 OK Content-type: text/html Set-Cookie: name=value; expires=date; path=/; domain=.rediff.com (content of page) GET /popular/ HTTP/1.1 Host: bookmarks.rediff.com Cookie: name=value Accept: */* expires=Fri, 31-Dec-2027 23:59:59
- 11. Session One type of state management mechanism A number of continuous request response sequences. The key is called SESSIONID PHPSESSID, ASPNETSESSIONID, jsessionid, SESSION_ID, mySESSID GET /popular/ HTTP/1.1 Host: bookmarks.rediff.com Cookie: PHPSESSID=4dy1q2e3d44c5dj343s3aq9
- 12. Moral of the story Programming languages are like religions All say same things Pray to same gods Keep up your spirits
- 13. Session Security Session id is like your browser’s password ‘non-guessable’ session id- even you can’t Random numbers? ‘Yet to solve’ mathematical problem. X is your ultra top secret algorithm. X sessionid CPU temperature Current date time Other junk stuff
- 14. Session Security And this algorithm can be as simple as MD5 or SHA1 These are called random hash code Irreversible id => pseudo random id Irreversible (only theoretically)
- 15. Forms Method for data transfer from client to server (part of HTTP methods) GET and POST GET Through URL Limited data POST – through HTTP Headers More (complex) data
- 16. HTTP Error codes 1xx – Informational 2xx – Success 200 OK 3xx – Redirection 304 Not Modified 4xx – Client Error 404 Not Found 5xx – Server Error 500 Server Error
- 17. Multi Tier App Web Server Internet Web Server - Static File Serving - Caching - Proxying Database Server - Storage of Data - Retrieval - Some Biz logic Database Server Application Server App Server - Biz Logic - Processing - Modifying Data J2EE, ASP.NET, PHP, RoR, Python Apache/TomCat, IIS, lightTPD MS SQL, MySQL, Oracle
- 18. Simple Question Netkode.com is hosted on 64.64.1.7 IP Will http://www.netkode.com Or http://64.64.1.7/ will load the page faster?
- 19. Believe me 3 Tier Architecture is NOT MVC (Model View Controller) Multi tier is an architecture concept MVC is a software design concept Excuse me. MVC?
- 20. MVC Presentation – View Logic – Controller Business Objects - Model
- 21. Which all are valid URLs http://cnn_india.com/index.asp https://cnnindia.com:8080/ http:// cnnindia.in /news 2007.asp http://wwww.cnn-india.co.in/
- 22. More Questions?
- 23. Thank You