1. Outline  Introduction to Application Layer  Peer-to-peer paradigm  Client-server paradigm  Domain Name System (DNS)  Flat-naming vs hierarchical-naming  DNS Protocol  World Wide Web (WWW)  WWW Architecture  Hypertext Transfer Protocol (HTTP)  Multimedia  Voice over IP (VoIP)

2. Peer-to-peer Paradigm The protocol machines are the same at both sides  The same state-flow diagram  The same set of tasks and responsibilities  The same set of capabilities Forms the basis of telephone network

3. Client-server Paradigm The tasks, capabilities and protocol machines are different at each side. Client-side requests service, Server-side provides service. Forms the basis of computer networks

4. Domain Name System (DNS) Flat Name Space: Each host in the network is unique and independent from each other. Hierarchical Name Space: Host have a composite names that are all hierarchically organised.

5. Domain Name System (DNS)

6. Part of the DNS name space showing the division into zones.

7. Domain Name System (DNS) Part of the DNS name space showing the division into zones.

8. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 25.10 Inverse domain

9. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 25.11 Recursive resolution

10. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 25.12 Iterative resolution

11. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 25.13 Query and response messages

12. Domain Name System (DNS) Either TCP or UDP protocols can be used to transport DNS messages :  If the DNS response is less than 512 bytes, UDP is used  Otherwise, a TCP connection must be set up.  In either case, port 53 is used by the DNS server.

13. WWW Architecture

14. Figure 27.14 Categories of Web documents

15. Figure 27.15 Static document

16. Figure 27.19 Dynamic document

17. Figure 27.20 Active document

18. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 27.1 HTTP transaction

19. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 27.8 Headers

20. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 27.9 Example 1

21. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 27.10 Example 2

22. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 27.10 Example 2

23. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 28.14 Time relationship

24. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 28.15 Jitter

25. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 28.16 Timestamp

26. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 28.1 Internet audio/video

27. Voice over IP The H323 architectural model for Internet telephony.

28. Voice over IP (2) The H323 protocol stack.

29. Figure 28.26 H.323 example

30. SIP – The Session Initiation Protocol The SIP methods defined in the core specification. Figure 28.21 SIP address formats

31. Figure 28.23 Tracking the callee

32. Comparison of H.323 and SIP