1. 12/05/2000CS590F, Purdue University1 Sip Implementation Protocol Presented By: Sanjay Agrawal Sambhrama Mundkur

2. 12/05/2000CS590F, Purdue University2 Contents Introduction Need for SIP Overview of the protocols in multimedia sessions SIP Services, Components and Operations Implementation building blocks Progress so far..

3. 12/05/2000CS590F, Purdue University3 Introduction Need for comprehensive multimedia control architecture for the internet Synchronous voice or multimedia communication between two or more parties, requires a means for prospective communications partners to find each other and to signal the other party their desire to communicate – IPTelephony Signalling Can be employed in Phone calls, multiparty conferences, video-on-demand, virtual presentations

4. 12/05/2000CS590F, Purdue University4 SIP over H.323 Complexity Scalability Extensibility SIP is a powerful, flexible, simple and scalable protocol that could serve as a real foundation for true wide area Internet telephony

5. 12/05/2000CS590F, Purdue University5 Protocols Session Initiation Protocol – for signaling Reservation Protocol – for reserving network resources Real-Time protocol – Transporting real-time data and providing QoS feedback Real-Time Streaming protocol – for controlling delivery of streaming media Session Advertising Protocol – advertising multimedia sessions via multicast Session Description Protocol – to describe multimedia sessions

6. 12/05/2000CS590F, Purdue University6 Session Initiation Protocol Application layer protocol for creating, modifying and terminating multimedia sessions Supports unicast, mesh and multicast conferences, and combination of these modes Similar to HTTP, Client-Server protocol, and text-based Provides reliability without assuming anything about the lower layer transport protocols

7. 12/05/2000CS590F, Purdue University7 Components User Agents User Agent Client User Agent Server Network Servers Registration Servers Proxy Servers Stateful Proxy Server Stateless Proxy Servers Redirect Servers

8. 12/05/2000CS590F, Purdue University8 Parser Sip messages are sent as text (Unicode characters) The Sip message grammar is given in the augmented BNF-form (RFC 2543) Syntax tree builder (JTBGJ) Parser Generator (Javacc)

9. 12/05/2000CS590F, Purdue University9 Protocol Building blocks User Agent A Registration Server User Agent B Proxy Server Location Server B’s current location Registration Server

10. 12/05/2000CS590F, Purdue University10 Registration SIP Client sends REGISTER message to the Registration server. Indicates the physical location REGISTER messages can be multicast (“sip.mcast.net” – 224.0.1.75) Serves as a simple locator service. REGISTER sip:belltell.com SIP/2.0 Via: SIP/2.0/UDP saturn.belltell.com From: sip:watson@belltell.com To: sip:watson@belltel.com CSeq: 1 REGISTER Call-ID: 70710@saturn.belltell.com Contact: sip:watson@globe..belltell.com:3890 Expires: 7200

11. 12/05/2000CS590F, Purdue University11 Name Translation, UserLocation SIP Addressing by a Sip URL (user@host:port)user@host:port Resolves host name through DNS server Checks if domain name refers to a host Mail exchange host User at a specific host derived through zero or more translations If called party is not at SIP server, can be directed or proxied (personal mobility)

12. 12/05/2000CS590F, Purdue University12 Session invitation Caller sends the request directly to UAS or to the nearest proxy server Proxy server uses the locator service to determine the next hop server Proxy forwards the request towards the callee Redirect server simply returns the alternate addresses INVITE sip:watson@ieee.org SIP/2.0 Via: SIP/2.0/UDP c.belltell.com From: sip:a.g.bell@belltell.com To:sip:watson@ieee.org Call-ID:23534@c.belltell.com23534@c.belltell.com Cseq:1 INVITE

13. 12/05/2000CS590F, Purdue University13 Session Invitation (cont.) If there are more than one locations to be contacted, the proxy forks the requests to all the locations. The callee’s response is propagated backwards the servers ( uses the Via header ) Stateful Proxy maintains the state according to the Call-ID. So forwards responses accordingly The caller sends ACK request following the response.

14. 12/05/2000CS590F, Purdue University14 Feature negotiation Allows a group of end systems to agree on the media to exchange and their respective parameters such as encodings. INVITE request has a listing of media types and associated encodings that the calling party is willing Called party responds with a subset of media types and encodings that it is willing to use Feature changes Subsequent INVITE request OPTIONS request

15. 12/05/2000CS590F, Purdue University15 Progress so far.. Study of the protocols used in IP Telephony Basic Implementation of SIP Parser UAS/UAC Proxy Server – Stateful and Stateless Redirect Server Registration Server