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SIP. 逄愛君 [email protected] Outline. SIP Overview SIP Components SIP Messages SIP Services SDP Conclusion. SIP Overview. Session Initiation Protocol The signaling protocol for creating, modifying and terminating sessions Session=audio, video…

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SIP

逄愛君

[email protected]


Outline
Outline

  • SIP Overview

  • SIP Components

  • SIP Messages

  • SIP Services

  • SDP

  • Conclusion


Sip overview
SIP Overview

  • Session Initiation Protocol

    • The signaling protocol for creating, modifying and terminating sessions

    • Session=audio, video…

  • IETF Proposed Standard (RFC 2543)

    • February 2, 1999

    • Currently under development within the Multiparty Multimedia Session Control (MMUSIC) working group


Sip overview1
SIP Overview

  • 15 Companies test interoperability between their equipment

    • April 1999

    • 3Com, Alcatel, Cisco, British, British Telecom, Columbia University, Dialogic, Ericsson, HP, Lucent, MCI, Nortel,…



Sip s role
SIP’s Role

SIP

Proxy

Media

Gateway

Controller

MGC

Signaling

Gateway

SIP

SG

sigtran

sigtran

to SS7

to SS7

IP Network

Megaco

Megaco

RTP

Media

Gateway

Media

Gateway

to PSTN

to PSTN

SIP

Client


Sip overview2
SIP Overview

  • Client-Server Model

  • Flexibility & Extensibility

    • Text-based Encoding

  • Transport Independence

    • UDP or TCP

  • Security

    • Secure Sockets Layer (SSL) for TCP-based SIP


Sip components
SIP Components

  • User Agents

    • Client (UAC)

      • To initiate a SIP request

    • Server (UAS)

      • To receive the request and return responses

  • Servers

    • Proxy

    • Redirect

    • Registrar


Addressing naming
Addressing & Naming

  • The entities addressed by SIP are users at hosts

    • email-like identifier of the form [email protected]

  • Examples

    • sip:[email protected]

    • sip:[email protected]


Sip messages
SIP Messages

  • Two kinds of SIP messages

    • Request and Response

  • Request message format

    • Request Line

      • Method, Request URI, Version

    • General, Request, Entity Headers

    • An Empty Line (CRLF)

      • Indicating the end of the header fields

    • Message Body

      • Session Description Protocol (SDP) : Optional


Sip messages cont d
SIP Messages(cont’d)

  • Response message format

    • Start-line

      • Status-Line

    • General, Response, Entity Headers

    • An Empty Line (CRLF)

      • Indicating the end of the header fields

    • Message Body

      • Session Description Protocol (SDP) : Optional


Methods
Methods

  • INVITE

    • The user is being invited to participate in a session.

  • ACK

    • The request confirms that the client has received a final response to an INVITE request.

  • BYE

    • The client wishes to release the call.


Methods cont d
Methods (cont’d)

  • OPTIONS

    • It queries the features the other side supports.

  • CANCEL

    • It cancels a pending request (not completed request).

  • REGISTER

    • It conveys the user’s location information to a SIP server.


Header fields
Header Fields

  • General

    • Apply to both request and response messages

  • Entity

    • Define information about the message body

  • Request

    • Allow the user agent client to pass additional information about the request

  • Response

    • Allow the user agent server to pass additional information about the response



Sip request example
SIP Request Example

INVITE sip:[email protected] SIP/2.0

Via: SIP/2.0/UDP science.fiction.com

From: Fingal <sip:[email protected]>

To: Patric <sip:[email protected]>

Call-ID: [email protected]

Cseq: 1 INVITE

Subject: lunch at La Empenada?

Content-Type: applcation/sdp

Content-Length: …




Sip response example
SIP Response Example

SIP/2.0 200 OK

Via: SIP/2.0/UDP sippo.example.se

Via: SIP/2.0/UDP science.fiction.com

From: Fingal <sip:[email protected]>

To: Patric <sip:[email protected]>

Call-ID: [email protected]

Cseq: 1 INVITE

Content-Type: applcation/sdp

Content-Length: …







Sip services
SIP Services

  • Similar to the Intelligent Network (IN) services

    • Call Transfer, Call Forwarding, Conference Calling, User Mobility…



Conclusion
Conclusion

  • SIP is a light-weight signaling protocol.

  • The amount of companies backing SIP is crucial for survival.

    • MCI (the biggest backer), 3Com, Lucent and DynamicSoft…

  • The low complexity level of the SIP, compared to H.323 (H.245 & H.225), should make companies interested.

  • 3G Wireless Technology

    • 3GPP-> H.323

    • 3GIP->SIP



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