introduction to sip(session initiation protocol)
DESCRIPTION
SIP is a VoIP protocol in Application Layer of OSI archTRANSCRIPT
Agenda
� Introduction
� Architecture
� SIP Message Format
� Call Flows
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
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
Architecture (2/2)
Request
Response
Server Client
SIP Message (1/8)
SIP Message
Message Headers
Request / Status Line
Message Body
C R L F
INVITE sip:[email protected]:5060 SIP/2.0
Via: SIP/2.0/UDP 22.3.56.790:5060;branch=z9G4bK0e8d
From: sip:[email protected]:5060
To: sip:[email protected]:5060
Call-ID: [email protected]
Cseq: 1 INVITE
Content-Type: applcation/sdp
Content-Length: 224
v=0o=jessica 0 0 IN IP4 10.7.1.229s=Session SDPc=IN IP4 10.7.1.229m=audio 5004 RTP/AVP 0 3 5a=rtpmap:0 PCMU/8000
SIP Message (2/8)
SIP
Request
Message Via: SIP/2.0/UDP 22.3.56.790:5060;branch=z9G4bK0e8d
From: sip:[email protected]:5060
To: sip:[email protected]:5060
Call-ID: [email protected]
Cseq: 1 INVITE
Content-Type: applcation/sdp
Content-Length: 224
INVITE sip:[email protected]:5060 SIP/2.0
v=0o=jessica 0 0 IN IP4 10.7.1.229s=Session SDPc=IN IP4 10.7.1.229m=audio 5004 RTP/AVP 0 3 5a=rtpmap:0 PCMU/8000
C R L F
SIP Message (3/8)
SIP Message (4/8)
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
� 6 Methods defined for request� REGISTER
� INVITE
� ACK
� BYE
� CANCEL
� OPTONS
SIP Message (6/8)
� Status codes
� Informational – 1xx
� Success – 2xx
� Redirection – 3xx
� Client-Error – 4xx
� Server-Error – 5xx
� Global-Failure – 6xx
SIP Message (7/8)
� Most header fields and its using are the same as that defined in HTTP and SMTP
SIP Message (8/8)
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
Registration
Registration_Register_request
Registration_Register_response
Request
Response
Registrar
User
Agent
Entity
Location
Server
Bob
192.0.2.4
use
store [email protected] : 192.0.2.4
Basic Call
1
2
3
4
5
6
Basic Call_message_1
Basic Call_message_2
Basic Call_message_3
Bob Off-hook
Basic Call_message_4
Basic Call_message_5
Bob On-hook
Basic Call_message_6
Basic Call_the session is terminated
Session with re-INVITE (IP Address Change)
9
6
F6
Session with re-INVITE – Bob’s Original IP address
F9
Session with re-INVITE – Bob’s new IP address
Unsuccessful --- No Answer
Unsuccessful --- Busy
Call
Hold
Call Hold_message_Request
F5
Call Hold_message_Response
F6
Three-Way Conference --- Third Party is Added
Three-Way Conference - Message_1
F5
F8
Three-Way Conference - Message_2
Three-Way Conference - start to 3-way conference
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