1. World Wide Web Aaditya Bhatia CS 147

2. Agenda History OSI model Hardware IP address DNS Server - Client Peer-to-peer Web-Sites Web programming Search engines Questions?

3. History 1960's o US DoD develops the world's first packet-switched network, ARPAnet, for resistance against nuclear attack. o First Universities gain access and inter-connections. 1970's o NSFNet developed o More Universities added to the network 1980's o The first commercial and private ISPs gain access to the network 1990's to Present o Technological advances increase individual access and perpetuates the internet's exponential growth.

4. OSI Model

5. TCP/IP vs OSI Not exactly the same Only 4 layers in TCP

6. Hardware Network Adapter Hub Switch Router Gateway Modem

7. Hardware - Network Adapter Connects a computer to another device Deals with OSI layers 1 and 2 Ethernet Wired o 10 Mbps o 100 Mbps o 1 Gbps 802.11 Wireless o a o b o g o n

8. Hardware - Hub Connects multiple devices Doesn’t manage packets Packet Collision Relatively slower

9. Hardware - Switch Layer 2 device Routes packets Packets don't collide Much faster Telephone exchange

10. Hardware - Router Creates an internal LAN Outer network - single IP Layer 3 device NAT - Masks the internal machines Routing table Wired or wireless

11. Hardware - Gateway

12. Hardware - Modem Modulator – Demodulator OSI layer 1 Relatively Slow Economical

13. IP Address Unique identifier 4 octets Assigned by o ISP o DHCP server o Network admin

14. DNS Domain Name System Address resolution Analogous to an phone book hostname => IP address

15. DNS - IP lookup

16. DNS - Address resolution

17. Server-client mode Request Response e.g. a website

18. Server Dedicated machine Serves multiple clients Handles incoming requests Provides services

19. Client Invokes remote services Generates request A workstation

20. Peer-to-peer Peers - equal Act as a server and a client Invoke and provide services e.g. BitTorrent

21. Web-Sites Web server o Apache Web browser o Firefox HTTP Protocol o Stateless connection o Simulated statefulness  Cookie  Server-side session

22. HTTP Protocol Stateless connection Simulated statefulness o Cookie o Server-side session

23. Web Programming HTML CSS Server Client AJAX

24. Web Programming - HTML HyperText Markup Language Content of websites Server response Understood by Browser Static content

25. Web Programming - CSS Cascading Style Sheet Defines style of a page Easily changeable or replaceable "Themes" CSS sample: p { color: red; font-size: 18px; }

26. Web Programming - Server Server side scripting o PHP o Perl o Python Programs that execute on server Access o Database o Internal systems Efficiency o Servers are faster

27. Web Programming - Client Client side scripting o DHTML o JavaScript Make changes to page after it has loaded o periodically o based on user input JavaScript sample: document.write( " Hello World " ); for( i = 0; i < 10; i++ ) alert( "Hello again " + i );

28. Web Programming - AJAX Asynchronous JavaScript And XML Update only a part of page with server's response Avoid multiple refreshes Lesser network traffic Example: Yahoo! Mail Counter example: SJSU eCampus

29. Search Engines Help find information Web pages Locations News Images etc. Crawl throughout the Internet Gather information continuously Key role in advertising market o Context-based ads

30. References http://en.wikipedia.org/ http://www.comptechdoc.org/ http://www.isoc.org/internet-history/

31. for your patience

32. Questions?