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Service Routing in 3GPP IP Multimedia Subsystem

Explore how 3GPP leverages SIP for service routing in the IP Multimedia Subsystem (IMS), covering architecture, implementation, and conclusions for efficient multimedia session handling. Discover the role of various components like CSCF servers, application servers, and SIP proxies in managing services within the IMS.

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Service Routing in 3GPP IP Multimedia Subsystem

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Presentation Transcript

  1. Agenda • Introduction to 3GPP • Introduction to SIP • IP Multimedia Subsystem • Service Routing in IMS • Implementation • Conclusions

  2. Service routing in 3GPP IP Multimedia Subsystem Teemu Jalava Supervisor: Raimo Kantola Instructor: M.Sc. Markus Isomäki, Nokia Research Center

  3. 3rd Generation Partnership Project (3GPP) • The 3rd Generation Partnership Project (3GPP) is a collaboration agreement that brings together a number oftelecommunications standards bodies and telecommunications companies. • Release ’99 was renamed Release 3 • Release 4 was out March 2001 • - IP network • Release 5 should be ready in summer 2002 • - IP multimedia • Release 6 • - All IP network

  4. 3GPP Network Architecture AS

  5. Session Initiation Protocol (SIP) • Creation, modification and termination of multimedia sessions • RCF 2543 -> RCF 3261 • Request - Reply based transactions • Easy to make new extensions • ASCII based, clear text, similar to HTTP • Uses UDP or TCP • URL addressing • sip:teemu.jalava@nokia.com Client 1 Proxy Client 2 INVITE INVITE 100 Trying 180 Ringing 180 Ringing 200 OK 200 OK ACK ACK Media streams BYE BYE 200 OK 200 OK

  6. SIP sample packet

  7. SIP Routing • SIP proxy takes care of user location resolving • teemu.jalava@nokia.com -> user1@130.233.20.40 • using registrar, DNS (ENUM in case of tel URL) or other means • DNS Service Resource Records (SRV RR) can be used to locate a SIP proxy in an other domain • via header is needed to ensure packets route the same way back • record-route header is needed is sertain proxies need to be in the routing path

  8. IP Multimedia Subsystem (IMS) Call State Control Function (CSCF) Interrogating-CSCF • Accesspoint to domain • Hides topology and configuration (User Agent) Serving-CSCF Proxy-CSCF • Session control services • Registration, AS usage, charging, etc • First contact point • Provides provicy control and QoS authorization • Local services, like emergency calls and local numbering

  9. IMS Session overview

  10. Application servers • Using: • Call Processing Lanquage (CPL) • SIP Common Gateway Interface (CGI) • SIP Servets • What: • Presence • Instant Messaging • Group services Roles: • SIP proxy • redirect server • Back-to-back-user-agent (B2BUA) • User Agent How: • Forking • SUBSCRIBE - NOTIFY • MESSAGE • Third party call control

  11. Application example: Presence • Presence enables user to express willingness and availability to communicate • Can be used with phonebook to make a "buddy list" • Presence updates with REGISTER method • Presence download with SUBSCRIBE - NOTIFY

  12. Example of service routing Example of service routing

  13. S-CSCF routing decisions • Based of Filter Criteria downloaded from Home Subscriber Server (HSS) at user registration • User profile • Filter Criteria • Address of the Application Server to be contacted. • Priority • Trigger Points (method, presence or apsence of any header, header content, etc) • Default Handling • Optional Service Information

  14. Implementation • Proof of concept work • S-CSCF from a SIP proxy • Adding filtering • Integrated user profile • Configuring user profile • Testing with network containing Presence AS, redirection AS and SIP-SMSGW

  15. Conclusions • SIP based services are easy to make and integrate to the IMS network • Configuration is easy • Scalable sollution, AS and S-CSCF duplication • Release 5 has been delayed from jan 2002 to june 2002, some features have been postponed to Release 6 • Some pressure from 3GPP to IETF to finalize new SIP RFC and SIP compression • These might have some impact to service routing issues

  16. Thank you! • Questions?

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