2. Internet Concept of protocols

3. INTERNET Internet Service Provider (ISP) has connected to the Internet

4. INTERNET You need a telephone line and a modem to connect to your ISP and then through ISP to Internet modem Telephone line

5. Connection to ISP Information provided by ISP for connection through modem modem dial-up number user name password ISP’s computer name

6. Why do you need a modem ?

7. Modem At the sender side, it change computer signal (digital) to telephone signal(analog) Signal is then transmitted through the telephone line At the receiver side, it can change back telephone signal (analog) to computer signal(digital)

8. INTERNET Two computers are connected through the Internet by use of modems

9. How do 2 computers communicate when they are connected through the Internet? They have their protocols to communicate

10. Hi ! How are you ? I am Computer X Computer X

11. Hi ! How are you ? I am Computer Y Computer Y

12. Computer Y ! How can I send messages to you ? Computer X

13. Computer X ! You can send messages to me by using protocols called TCP/IP. Computer Y

14. Computer Y ! TCP/IP can divide messages into packets and arrive to you safely What is your IP address? Computer X

15. Computer X! My IP address is 250.143.035.001 But humans call me compy.com.hk because a group of numbers is difficult to remember for human being. What is your IP address? Computer Y

16. Computer Y! My IP address is 250.143.075.255 But human calls me compx.com.hk Can I send messages to you now? Computer X

17. Computer X! Now, you can send your messages according to my IP address Computer Y

18. Computer Y! Since your IP address is unique, I can send messages to you now Are you ready? Computer X

19. Computer X! Now, I am ready Computer Y

20. Computer Y! I am sending now... Computer X

21. Protocol A standard rule governing the communication between 2 computers For example –TCP (Transmission Control Protocol) –IP (Internet Protocol) –HTTP (Hypertext Transfer Protocol)

22. Domain Name Every Internet server has IP address It consists of 4 octets, which is very precise (e.g. 250.143. 35.1) But humans have trouble with remembering numbers and they prefer to use meaningful text address (e.g. compy.com.hk)

23. I want to access the internet resources. What should I need in order to connect the Internet?

24. You need ISP telephone line and a modem a browser URL

25. Terms Internet Service Provider (ISP) –a company that gives you access to the Internet for a feE Uniform Resource Locator(URL) –an address that identifies a server, a directory or a specific file such as HTTP URLs orWeb addresses Browser –a program that lets you view and explore information on the Web such as Internet Explorer or Netscape Communicator