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SIP

SIP. 逄愛君 ijpong@pcs.csie.nctu.edu.tw. 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

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  1. SIP 逄愛君 ijpong@pcs.csie.nctu.edu.tw

  2. Outline • SIP Overview • SIP Components • SIP Messages • SIP Services • SDP • Conclusion

  3. 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

  4. 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,…

  5. SIP Architecture

  6. 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

  7. SIP Overview • Client-Server Model • Flexibility & Extensibility • Text-based Encoding • Transport Independence • UDP or TCP • Security • Secure Sockets Layer (SSL) for TCP-based SIP

  8. SIP Components • User Agents • Client (UAC) • To initiate a SIP request • Server (UAS) • To receive the request and return responses • Servers • Proxy • Redirect • Registrar

  9. Addressing & Naming • The entities addressed by SIP are users at hosts • email-like identifier of the form user@host • Examples • sip:patrik@example.com • sip:beagleboy@176.7.6.1

  10. 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

  11. 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

  12. 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.

  13. 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.

  14. 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

  15. SIP Headers

  16. SIP Request Example INVITE sip:pgn@example.se SIP/2.0 Via: SIP/2.0/UDP science.fiction.com From: Fingal <sip:ffl@fiction.com> To: Patric <sip:pgn@example.se> Call-ID: 1234567890@science.fiction.com Cseq: 1 INVITE Subject: lunch at La Empenada? Content-Type: applcation/sdp Content-Length: …

  17. Response

  18. Response (cont’d)

  19. 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:ffl@fiction.com> To: Patric <sip:pgn@example.se> Call-ID: 1234567890@science.fiction.com Cseq: 1 INVITE Content-Type: applcation/sdp Content-Length: …

  20. Invitation for SIP Proxy

  21. Invitation for Redirect Server

  22. SIP+ISDN (Q.931)

  23. SIP+MGCP

  24. SIP / MGCP / ISUP

  25. SIP Services • Similar to the Intelligent Network (IN) services • Call Transfer, Call Forwarding, Conference Calling, User Mobility…

  26. SIP Mobility

  27. 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

  28. Discussion

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