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)

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.

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Figure 25.10 Inverse domain

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Figure 25.11 Recursive resolution

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Figure 25.12 Iterative resolution

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Figure 25.13 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 27.14 Categories of Web documents

Figure 27.15 Static document

Figure 27.19 Dynamic document

Figure 27.20 Active document

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Figure 27.1 HTTP transaction

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Figure 27.8 Headers

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Figure 27.9 Example 1

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Figure 27.10 Example 2

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Figure 27.10 Example 2

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Figure 28.14 Time relationship

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Figure 28.15 Jitter

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Figure 28.16 Timestamp

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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 28.26 H.323 example

SIP – The Session Initiation Protocol

The SIP methods defined in the core specification.

Figure 28.21 SIP address formats

Figure 28.23 Tracking the callee

Comparison of H.323 and SIP