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SIP and the application of SIP as used in 3GPP

Learn the application of SIP in 3GPP architecture, functionality, and network elements like P-CSCF, I-CSCF, and S-CSCF. Discover the SIP protocol's essential role in 3GPP services.

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SIP and the application of SIP as used in 3GPP

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  1. SIP and the application of SIP as used in 3GPP Keith Drage - Lucent Technologies

  2. Overview of the 3GPP IM CN subsystem architecture • Independent of the access mechanism • Mobility provided by underlying access mechanism • Functional entities use IPv6 • Functionality apportioned between visited network and home network • Home network control of services

  3. Overall 3GPP architecture IM CN subsystem GPRS

  4. User IPv6 Application Server GGSN Terminal UTRAN Core Network Transport IPv6 GPRS - user plane versus transport plane • User and transport planes are completely independent, i.e. the transport plane can run on a different IP version than the user plane • UTRAN and Core Network transport can also run on different IP versions

  5. User IPv6 (PDP type IPv6) Application Server UTRAN SGSN GGSN Terminal GPRS - Transport of user IP packets in UMTS Radio Bearer GTP-U GTP-U IP packets to/from the terminal are tunneled through the UMTS network, they are not routed directly at the IP level.

  6. 3GPP requires multiple outbound proxies REG REG REG UA P-CSCF I-CSCF S-CSCF 200 OK 200 OK 200 OK Home network User equipment Visited network Home network P-CSCF - Proxy CSCF (Call Session Control Function). The terminals point of contact in the visited network after registration. Point where network places constraint on the bearer. I-CSCF - Interrogating-CSCF. Responsible for finding the S-CSCF at registration. May also perform hiding of the S-CSCF network architecture. S-CSCF - Serving-CSCF. Responsible for identifying user’s service privileges. Responsible for selecting access to home network application server (service platform) and for providing access to that server.

  7. Example allocation of functional entities - mobile to mobile User A A’s visited network Required onregistration,optional on sessiion establish A’s home network GPRS S-CSCF P-CSCF I-CSCF I-CSCF Optional User B I-CSCF GPRS I-CSCF P-CSCF Required onregistration,optional on sessiion establish S-CSCF B’s home network B’s visited network

  8. Example allocation of functional entities - PSTN to mobile MGW User B MGCF GPRS I-CSCF P-CSCF Required onregistration,optional on sessiion establish S-CSCF B’s home network B’s visited network

  9. Example allocation of functional entities - mobile to PSTN User A A’s visited network Required onregistration,optional on sessiion establish A’s home network GPRS S-CSCF P-CSCF I-CSCF BGCF MGW BGCF SGW MGCF Breakout network

  10. Provision of services SIP Application Server Sh ISC Sh OSA API OSA Service OSA Cx ISC S-CSCF HSS Capability Server Application (SCS) Server ISC IM SSF ISC interface runs the SIP protocol MAP CAP CAMEL Service Environment

  11. Summary of architecture SLF HSS AS Cx Cx Dx Gm Mw Mw UA P-CSCF I-CSCF S-CSCF Mg Mg Mg BCGF MGCF Mc MGW

  12. Key 3GPP documents and their location on 3GPP servers • TS 23.228: "3rd GPP; Technical Specification Group Services and System Aspects; IP Multimedia (IM) Subsystem - Stage 2". • TS 24.228: "3rd GPP; Technical Specification Group Core Network; Signalling flows for the IP multimedia call control based on SIP and SDP". • TS 24.229: "3rd GPP; Technical Specification Group Core Network; IP Multimedia Call Control Protocol based on SIP and SDP". • TS 23.218: "3rd GPP; Technical Specification Group Core Network; IP Multimedia (IM) Session Handling; IP Multimedia (IM) call model” These drafts can be found at the 3gpp web site either at: • ftp://ftp.3gpp.org/Specs/Latest_drafts/ • ftp://ftp.3gpp.org/Specs/2001-06/Rel-5 depending on the status of the document

  13. Issues for SIP

  14. Multiple outbound proxies - path Insert P-CSCFaddress Add I-CSCFaddress StoreP-CSCF andI-CSCF addresses REG REG REG UA P-CSCF I-CSCF S-CSCF 200 OK 200 OK 200 OK StoreS-CSCF and I-CSCF addresses Add S-CSCFaddress

  15. Compression • Efficient use of bandwidth is required on the radio interface. • Will be applied to both the media streams (header compression or removal) and to the signalling bearers. • Compression / decompression of SIP will be performed by the UE and the P-CSCF. • These entities will also perform integrity protection on the signalling bearer.

  16. Other issues still in discussion at requirements level • Emergency calls, and support of location based services, requires the transfer of location information (needs GEOPRIV to complete). • Interworking with external SIP environments requires transcoding support. Default codec for 3GPP is the AMR codec. • There are functional entities which have not been shown in these slides which will require SIP support, e.g. MRF.

  17. Questions

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