03/09/2003helsinki university of technology1 overview of thesis topic presented by: zhao xuetao
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Overview of Thesis Topic
Presented By:Zhao Xuetao
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Contents SIP protocol Real-time services Presence Other tasks
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SIP Protocol
Overview of the protocols in multimedia sessions
SIP Services, Components and Operations
Implementation building blocks
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Protocols Session Initiation Protocol – for signaling Reservation Protocol – for reserving network
resources Real-Time protocol – Transporting real-time data
and providing QoS feedback Real-Time Streaming protocol – for controlling
delivery of streaming media Session Advertising Protocol – advertising
multimedia sessions via multicast Session Description Protocol – to describe
multimedia sessions
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Session Initiation Protocol
Application layer protocol for creating, modifying and terminating multimedia sessions
Supports unicast, mesh and multicast conferences, and combination of these modes
Similar to HTTP, Client-Server protocol, and text-based
Provides reliability without assuming anything about the lower layer transport protocols
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Components User Agents
User Agent Client User Agent Server
Network Servers Registration Servers Proxy Servers
Stateful Proxy Server Stateless Proxy Servers
Redirect Servers
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Parser
Sip messages are sent as text (Unicode characters) The Sip message grammar is given in the
augmented BNF-form (RFC 2543) Syntax tree builder (JTBGJ) Parser Generator (Javacc)
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Protocol Building blocks
User Agent A
RegistrationServer
User Agent BProxy Server
Location Server
B’s current location
RegistrationServer
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Real-time Services Real-time services situation in Ad Hoc
networks Implementation of audio/video services
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Real-time Services Challenges in Ad Hoc networksAd hoc networks pose a great challenge to audio/video
transport. The main problems are:1.Frequently changing topology makes the established link
likely broken, which may cause interruption, pause, or jerkiness in the received signal.
2. Other factors that influence quality include radom packet loss caused by wireless channel errors and small capacity of a wireless network.
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Real-time services
Video transport typically requires strict bandwidth and delay
guarantees. However it is very hard to maintain end-to-end
route which is both stable and has adequate bandwidth in Ad
Hoc netwoks. Furthermore, compressed video is susceptible
to transmission errors.
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Real-time Services Include voice session in SIP client1) Integrate RAT (Robust Audio Tool) that contains
RTP/RTCP stack.
2) Develop a testing and validation use case for audio sessions. Collect audio measurements for performance analysis of audio sessions in Ad Hoc networks.
3) Propose a new transport protocol based on performance analysis.
Implementation of video session???
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Presence What is presence? Why do we use SIP as presence protocol? How it works to achieve presence
infomation? Future task
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What is presence? Presence known as presence infomation, conveys the
ability and willingness of a user to communicate across a set of devices.
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SIP as presence protocol SIP is a best choice as a presence protocol because actually
presence information is already in SIP location services as registrations
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How it works? SIP could contact the server that contains registration state
for a user when any user requests the presence information. The registration state is a key component of user presence, SIP networks can route SUBSCRIBE requests to the same server. Thus global connectivity for presence subscriptions and notifications is established through reuse of SIP networks.
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Future Task Include Presence with location information. This
will consist of using SIP client for implementing a local presence server with databases containing presence information of neighbour Ad Hoc nodes.
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Other Tasks Include other services in SIP client 1. Include Chat and conferencing service. This will consist
of using SIP client for implementing chat server that includes databases for storing group information for initiating a chat or conference in Ad Hoc networks.
2. Performance testing of multimedia services in Ad Hoc networks (audio/video and presence). Based on the performance tests you would propose some solutions for enhancing the QoS for multimedia services.