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)

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

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

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.

Domain Name System (DNS)

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

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

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

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

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

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

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.

WWW Architecture

Figure Categories of Web documents

Figure Static document

Figure Dynamic document

Figure Active document

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

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

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

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

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

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

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

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

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

Voice over IP The H323 architectural model for Internet telephony.

Voice over IP (2) The H323 protocol stack.

Figure H.323 example

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

Figure Tracking the callee

Comparison of H.323 and SIP