Introduction to SIP(Session Initiation Protocol)
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Session Initiation Protocol (SIP) is a signaling protocol for managing multimedia communication sessions over Internet Protocol (IP) networks. SIP can be used to establish two-party or multiparty sessions that include voice, video, chat, gaming, and other forms of media. The document introduces SIP architecture, message format, and common call flows including registration, basic call setup, call modification, call hold, and three-way conferencing.
Introduction to SIP(Session Initiation Protocol)
- 1. Introduction to Session Iinitiation Protocol (a VoIP protocol) 2007-10-16William.L wiliwe@gmail.com
- 3. Introduction An application-layer signaling protocol Create, Modify, and Terminate sessions SIP is ASCII text-based SIP incorporates elements of two widely used Internet protocols: HTTP SIP borrowed a client-server design and the use of URLs and URIs SMTP SIP borrowed a text-encoding scheme and header style SIP uses e-mail-like names for addresses UserName@Host-Domain
- 4. Architecture (1/2) Client-Server architecture --- the same as HTTP Client originates message Server responds to or forwards message Elements SIP User Agents takes direction or input from a user and acts as an agent on their behalf to set up and tear down media sessions with other user agents. SIP Servers Registrar Proxy Redirect
- 6. SIP Message (1/8) SIP Message Message Headers Request / Status Line Message Body C R L F
- 7. INVITE sip:allen@10.7.1.228:5060 SIP/2.0 Via: SIP/2.0/UDP 22.3.56.790:5060;branch=z9G4bK0e8d From: sip:carol@22.3.56.790:5060 To: sip:bob@22.3.56.789:5060 Call-ID: 1234567890@10.8.2.106 Cseq: 1 INVITE Content-Type: applcation/sdp Content-Length: 224 v=0 o=jessica 0 0 IN IP4 10.7.1.229 s=Session SDP c=IN IP4 10.7.1.229 m=audio 5004 RTP/AVP 0 3 5 a=rtpmap:0 PCMU/8000 SIP Message (2/8)
- 8. SIP Request Message Via: SIP/2.0/UDP 22.3.56.790:5060;branch=z9G4bK0e8d From: sip:carol@22.3.56.790:5060 To: sip:bob@22.3.56.789:5060 Call-ID: 1234567890@10.8.2.106 Cseq: 1 INVITE Content-Type: applcation/sdp Content-Length: 224 INVITE sip:allen@22.3.56.789:5060 SIP/2.0 v=0 o=jessica 0 0 IN IP4 10.7.1.229 s=Session SDP c=IN IP4 10.7.1.229 m=audio 5004 RTP/AVP 0 3 5 a=rtpmap:0 PCMU/8000 C R L F SIP Message (3/8)
- 10. GET /2001/Talks/0710-ep-grid/all.htm,access HTTP/1.1 User-Agent: W3C ChACL agent Host: www.w3.org Accept: text/xml Accept-Encoding: deflate, gzip, x-gzip, identity, *;q=0 Authorization: Basic xxxxxxxxxxxxxxxxxxxx Connection: Keep-Alive, TE TE: deflate, gzip, chunked, identity, trailers HTTP Message Request HTTP/1.0 200 Date: Sat, 07 Jul 2001 14:08:12 GMT Server: Apache/1.3.6 (Unix) PHP/3.0.15 WWW-Authenticate: Basic realm="W3CACL“ Content-length: 301 Content-Type: text/xml<?xml version="1.0"?> <!-- Session-Id: 994514895.830925 --><rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:s="http://www.w3.org/2001/02/acls/ns#"> <rdf:Description aboutEach="#B1"> <s:hasAccessTo rdf:resource="http://www.w3.org/2001/Talks/0710-ep-grid/all.htm"/> </rdf:Description></rdf:RDF> HTTP Message Response SIP Message (5/8) SIP messages’ format is the same as HTTP ones
- 11. 6 Methods defined for request REGISTER INVITE ACK BYE CANCEL OPTONS SIP Message (6/8)
- 12. Status codes Informational – 1xx Success – 2xx Redirection – 3xx Client-Error – 4xx Server-Error – 5xx Global-Failure – 6xx SIP Message (7/8)
- 13. Most header fields and its using are the same as that defined in HTTP and SMTP SIP Message (8/8)
- 14. Call Flows Registration Basic Call Re-INVITE – modify the session’s parameter No Answer – use CANCEL method Busy Call Hold 3-way Conference -- The third party is added
- 15. Registration
- 18. Request Response bob@biloix.com Registrar User Agent Entity Location Server Bob 192.0.2.4 use store bob@biloix.com : 192.0.2.4
- 27. Basic Call_the session is terminated
- 28. Session with re-INVITE (IP Address Change) 9 6
- 29. F6 Session with re-INVITE – Bob’s Original IP address
- 30. F9 Session with re-INVITE – Bob’s new IP address
- 31. Unsuccessful --- No Answer
- 33. Call Hold
- 36. Three-Way Conference --- Third Party is Added
- 37. Three-Way Conference - Message_1 F5
- 38. F8 Three-Way Conference - Message_2
- 39. Three-Way Conference - start to 3-way conference
- 40. References RFC-3261 SIP:Session Initiation Protocol Understanding the Session Initiation Protocol, Alan B. Johnstone , 2/e, 2004 draft-ietf-sipping-service-examples-10.txt, March 5, 2006 draft-ietf-sipping-conferencing-models-01.txt, January 2003 RFC 3665 Session Initiation Protocol (SIP) Basic Call Flow Examples, , December 2003 http://www.in2eps.com/xrai/ztk-ietf-wg-rai-sip.html