Agenda Overview of SIP SIP Functions & Features SIP Architecture SIP Components SIP Server Modes Sample SIP call scenario SIP Requests & Responses Protocols used with SIP Summary & Conclusion 2
Overview of SIP A signaling protocol used to create, manage and terminate sessions in IP network A standard protocol defined by IETF IETF mapped it as Application-layer protocol in OSI layer Similar to HTTP & SMTP protocol in syntax URI: SPI: email@example.com It is extensible But doesn’t provide end-to-end functionality 3
SIP Functions & Features User Location Address Resolution: translate URIs to current IP address User Availability User can control certain types of communication status User Capabilities Determining the features available by both parties’ programs Session Setup a three-way handshake Session Management Able to modify session in use 4
SIP Functions & Features(Cont. ) Registration Users can register themselves using their ID, independent from the device registration Redirect SIP server can redirect a request to another address Forking Request forwarding: Serial & Parallel Forking Proxy Proxy server can forward the request of the user to another one Mobility SIP calls can set up if proper gateways are provided 5
SIP Architecture SIP Components User Agents Can act as User Agent Client (UAC) and User Agent Server (UAS) SIP Endpoints: Softphone, SIP phone, Smart Phone, PDA SIP Servers Registrar Authenticate and register UA’s location and status Proxy Forward request to other computers. Involve in session setup and teardown Redirect Redirect clients to UAs they are attempting to contact. Also can fork a call. Location Services A database that used to keep information about users’ registration and their locations 6
SIP Architecture(cont.) SIP Server Modes Stateful vs Stateless SIP server can run in one of these two modes Stateful server keep track of all requests and responses Stateless server found as part of backbone Client/server vs P2P 7
SIP Requests & Responses SIP Response Packet SIP/2.0 100 Trying (180 Ringing, 200 OK) From: ”BOB" <sip:firstname.lastname@example.org> To: <sip:email@example.com> Call-ID: 490dffec2cafa2772a11eec8716e CSeq: 102 INVITE User-Agent: middleserver Max-Forwards: 30 Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBEBYE, REFER, SUBSCRIBE 1xx : Informational 2xx Success: request successful 3xx Redirection : request should tried another location 4xx Client Error: an error in request 5xx Server Error: an error in recipient 6xx Global Failure : request has failed and should not be retried again12
Protocols used with SIP User Datagram Protocol (UDP) used to send datagrams over IP network Transport Layer Security (TLS) provides security between applications Session Description Protocol (SDP) used to send description information when sending multimedia data Real-Time Transport Protocol (RTP) used to transport real-time data across a network Media Gateway Control Protocol (MGCP) used to control gateways that provide access to the PSTN Real-Time Streaming Protocol (RTSP) used to control the delivery of streaming media SIMPLE (SIP for Instant Messaging and Presence Leveraging Extensions) 13
Summary & Conclusion A fundamental building block for real-time communication SIP is an open standard and development community is trying for higher interoperability Research going for further enchantments and solutions to known issues 14
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