Presentation on theme: "SIP Overview. SIP2 Contents What is Sip? SIP Benefits SIP message structure SIP components SIP mobility."— Presentation transcript:
SIP2 Contents What is Sip? SIP Benefits SIP message structure SIP components SIP mobility
SIP3 What is SIP? Sip is signaling protocol defined by the Internet Engineering Task Force (IETF) for initiating, managing and terminating voice and video sessions across packet networks A textual based client-server protocol Application layer protocol It s not Transport Protocol It s not QoS Reservation Protocol
SIP4 SIP history Work began in 1995 in IETF mmusic WG 03/1999: RFC 2543, 153 pages, 6 methods 11/1999: SIP WG formed 11/2000: draft-ietf-sip-rfc2543bis-02, 171 pages, 6 methods
SIP5 SIP benefits Integration with existing protocols Integration well with Web(Http) and (Smtp) Simplicity Simple protocol vs H.323 Textual based, so parsing generation are simple Extensibility HTTP and SMTP extensibility Modularity Initiation,termination,change,user location, basic registration. Separating notion of a session to invite a user Scalability Off DNS, BGP Server processing.
SIP6 SIP Messages SIP Requests: INVITE – Initiates a call by inviting user to participate in session. ACK - Confirms that the client has received a final response to an INVITE request. BYE - Indicates termination of the call. CANCEL - Cancels a pending request. REGISTER – bind a permanent address to current location OPTIONS – Used to query the capabilities of a server.
SIP7 SIP Response Codes 1yzInformational 100 Trying 180 Ringing (processed locally) 181 Call is Being Forwarded 2yzSuccess 200 ok 3yzRedirection 300 Multiple Choices 301 Moved Permanently 302 Moved Temporarily 4yzClient error 400 Bad Request 401 Unauthorized 404 Not Found 405 Method not Allowed 407 Proxy Authentication Required 415 Unsupported Media Type 482 Loop Detected 486 Busy Here 5yzServer failure 500 Server Internal Error 6yzGlobal Failure 600 Busy Everywhere
SIP8 Invite Message Example INVITE SIP/2.0 Via: SIP/2.0/UDP here.com:5060 From: BigGuy To: LittleGuy Call-ID: CSeq: 1 INVITE Subject: Happy Christmas Contact: BigGuy Content-Type: application/sdp Content-Length: 147 Response Status SIP/ OK Via: SIP/2.0/UDP here.com:5060 From: BigGuy To: LittleGuy ;tag=65a35 Call-ID: CSeq: 1 INVITE Subject: Happy Christmas Contact: LittleGuy Content-Type: application/sdp Content-Length: 134 Request Method receive RTP G.711-encoded audio at :49172 v=0 o=UserA IN IP4 here.com s=Session SDP c=IN IP t=0 0 m=audio RTP/AVP 0 a=rtpmap:0 PCMU/8000 v=0 o=UserB IN IP4 there.com s=Session SDP c=IN IP t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 Message Header Fields Payload
SIP9 Address Header Fields From: message originator To: final recipient Request-URI: current destination; may change along signaling path Contact: appears in INVITE / OPTIONS / ACK / REGISTER requests and in responses. It indicates direct response address to which subsequent transactions are sent. A UA may send subsequent BYE or ACK to Contact: address (unless configured to use an outbound proxy). It includes redirection address in 3xx and 485 responses. It includes additional error information in 4xx, 5xx, and 6xx responses. It may include preference weights. It includes current location in REGISTER requests. Multiple Contact: header fields may be included.
SIP10 Session Description Protocol (SDP) Convey sufficient information to enable participation in a multimedia session SDP includes description of: Session name and purpose Times the session is active Media to use Information where to send and receive media Contact information
SIP11 Session Description Protocol (SDP) o=sisalem IN IP s=SIP Example c=IN IP v=0 t= m=audio RTP/AVP 0 a= rtpmap:0 PCMU/8000
SIP12 SIP Distributed Architecture Redirect Server Location Server Registrar Server User Agent Proxy Server SIP/PSTN Gateway PSTN SIP Components Proxy Server H.323 SIP/H.323 Gateway
SIP13 SIP Components User agent(user application) UA Client(caller) UA Server(called party) Proxy Server Redirect Server Register
SIP14 User Agents An application that initiates, receives and terminates calls. User Agent Clients (UAC) – An entity that initiates a call. User Agent Server (UAS) – An entity that receives a call. Both UAC and UAS can terminate a call. Both SW and HW available
SIP15 Proxy Server An intermediary program that acts as both a server and a client to make requests on behalf of other clients. Requests are serviced internally or by passing them on, possibly after translation, to other servers. Interprets, rewrites or translates a request message before forwarding it. Stateless proxy server No information about the message is stored Stateful proxy server Forking reliability
SIP16 SIP Operation in Proxy Mode User on left-hand side is initiating a call to on right-hand side; Callee registered with his server previously Location Server Proxy/Registrar INVITE From: To: sip: Call-ID: #4 INVITE From: To: sip: Call-ID: #1 #3 Callee #2 OK 200 From: To: sip: Call-ID: #5 OK 200 From: To: sip: Call-ID: #6 ACK #7 Media stream #8
SIP17 Location Server A location server is used by a SIP redirect or proxy server to obtain information about a called partys possible location(s). Locating service LDAP SQL
SIP18 Redirect Server After location service to look up a user, location information is sent back to the caller in a redirection class response, which concludes the transaction. Unlike a proxy server, the redirect server does not forward SIP request. Unlike a user agent server, the redirect server does not accept or terminate calls.
SIP19 SIP Operation in Redirect Mode Redirect Server/Location Server Proxy ACK #8 Callee #2 INVITE #1 302 moved temporarily Contact: #4 #3 INVITE #6 ACK #5 OK 200 #7
SIP20 Registrer Server A server that accepts REGISTER requests. The register server may support authentication. A registrer server is typically co-located with a proxy or redirect server and may offer location services.
SIP21 SIP Registration
SIP22 Simplified SIP Call Setup and Teardown 302 (Moved Temporarily) INVITE 200 (OK) ACK INVITE 302 (Moved Temporarily) ACK INVITE 180 (Ringing) 200 (OK) ACK RTP MEDIA PATH BYE 200 (OK) Call Teardown Media Path Call Setup INVITE Location/Redirect ServerProxy Server User Agent INVITE
SIP23 SIP and Terminal Mobility Home Network HP Visited Network FP Signalling Cell 2 Cell 1 REGISTER #1 REGISTER #2
SIP24 SIP and Terminal Mobility Home Network HP Visited Network FP Signalling Data Cell 2 Cell 1 INVITE #1 INVITE #2 INVITE #3 #4
SIP25 SIP and Terminal Mobility Home Network HP Visited Network FP Signalling Data Cell 2 Cell 1 REGISTER #3 REGISTER #2 #1 reINVITE #3 #4