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IP Multimedia Standardization

IP Multimedia Standardization. Standards Group August 2002. Outline. IP Multimedia Standardization in 3GPP and 3GPP2 3GPP IP Multimedia Subsystem (IMS) 3GPP2 IP Multimedia Domain (MMD) IP Core Network Harmonization Session Initiation Protocol (SIP) Internet Multimedia Protocols

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IP Multimedia Standardization

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  1. IP Multimedia Standardization Standards Group August 2002

  2. Outline • IP Multimedia Standardization in 3GPP and 3GPP2 • 3GPP IP Multimedia Subsystem (IMS) • 3GPP2 IP Multimedia Domain (MMD) • IP Core Network Harmonization • Session Initiation Protocol (SIP) • Internet Multimedia Protocols • SIP Operations • SIP Messages • 3GPP IMS Architecture • 3GPP2 MMD Architecture (with IMS subset.)

  3. 3GPP IP Multimedia Subsystem • Started with All-IP Workshop in February 2000 in Sophia Antipolis. • Original goals included: • Operator cost saving • Less expenditure on circuit switched equipment • Common specification for IP multimedia equipment • Independence of wireless access technology • Flexibility in service creation • Allow 3rd party applications • Gain from Internet services • Integrated multimedia services over IP • 3GPP IP Multimedia Subsystem (IMS) • Declared to be completed in June 2002 as part of Release 5. • The specs are not stable and will undergo significant changes. • Call control based on IETF SIP (Session Initiation Protocol) • No significant services have yet been defined over IMS • Have strong influence on IETF SIP standardization • Pulled in IETF SIP standardization schedule. • Influenced the IETF procedure for adding SIP extensions.

  4. 3GPP2 IP Multimedia Domain • 3GPP2 All-IP Adhoc group: • Formed in early 2000, shortly after the 3GPP All-IP workshop • Similar goals as 3GPP IMS, plus: • Use IETF protocols in the network instead of IS-41 • Initial release of documents in November 2000: • Network Architecture • Service Requirements. • Stage 2 similar to 3GPP • 3GPP2 has also developed Legacy MS Domain: uses SIP-T between softswitch MSCs, no MS changes.

  5. IP CN Harmonization (1) • Meeting proposed by Operators Harmonization Group • Held in Toronto, April 3-4, 2002 • Co-chaired by 3GPP and 3GPP2 officials • Results were non-binding to 3GPP and 3GPP2 • Recommendations from the meeting: • Common OSA/Parlay APIs • Single IMS reference model with common terminology • No impacts on 3GPP Release 5 IMS • 3GPP2 to adopt 3GPP Rel-5 IMS and Parlay 3.1 as base • Establish mechanisms to promote harmonization • Consider joint development of specifications.

  6. IP CN Harmonization (2) • 3GPP2 follow-up: • 3GPP2 TSG-N joined the joint working group of Parlay/OSA. • Having joint meetings to develop joint IMS specifications is preferred. • TSN-N invited 3GPP to another workshop "to establish a strategy and working agreement on collaboration on a set of common specifications for Release 6 and beyond" • 3GPP follow-up: • PCG (Project Coordination Group) symbolically “endorsed harmonization recommendations in principle”, with conditions such as “under no circumstances should 3GPP work be slowed down”. • 3GPP CN and SA plenaries in June 2002 decided on the following: • No joint meetings for IMS • No change to 3GPP working procedures • No joint email list for IMS • 3GPP will develop the common part of IMS specifications. • 3GPP2 member companies may bring contributions to 3GPP meetings. • In summary, 3GPP wants to maintain full control over IMS standardization.

  7. IP CN Harmonization (3) • Potential technical issues with IMS harmonization: • IPv4 versus IPv6 • Different vocoders • Different QoS procedures • Different packet data access technologies, such as GPRS versus 3GPP2 packet data service and Mobile IP. • HSS versus AAA and HLR • Subscription storage on mobile • IMS interaction with Mobile IP

  8. Internet Multimedia Protocols • IETF suite of Internet Multimedia Protocols: • Real Time Transfer Protocol (RTP) • Session Description protocol (SDP) • Session Initiation Protocol (SIP) • Real Time Streaming Protocol (RTSP) • Synchronized Multimedia Integration Language (SMIL) • Etc… • SIP is the signaling protocol for multimedia session establishment. It has also been extended to support other applications such as presence and instant messaging.

  9. Example Services Enabled by SIP • Value-added telephony services based on signaling • E.g. IN services, PBX features, CLASS services • Real-time multimedia communication • Multimedia conferencing, gaming, and work sharing • Personal mobility between different terminals and networks • Presence and Instant Messaging • 3rd party call control • Flexible service creation environment • E-commerce • IP-based video streaming • Computer-Telephony Integration (CTI)

  10. SIP Trapezoid DNS Server Location Service Signaling Flow Outbound SIP Proxy Inbound SIP Proxy Media Flow Calling User Agent Called User Agent

  11. SIP Session Establishment • User location • determination of the end system to be used for communication; • User availability • determination of the willingness of the called party to engage in communications; • User capabilities • determination of the media and media parameters to be used; • Session setup • "ringing", establishment of session parameters at both called and calling party; • Session handling • including transfer and termination of sessions, modifying session parameters, and invoking services.

  12. Wireline vs. Wireless SIP Usage • Wireline SIP assumptions • High processing power • Easily upgraded • Bandwidth plentiful • Wireless terminal properties • Limited processing power • Limited bandwidth • SIP characteristics • Large messages, with inefficient text encoding • Favoring generality and modularity over efficiency • Potentially chatty message exchanges • SIP adaptation for wireless terminals • SIP message compression • Service implementation on SIP servers  • Use of SIP proxy servers instead of SIP redirect servers.

  13. SIP Methods • INVITE Used for Session Setup • ACK Acknowledgement of final response to INVITE • BYE Session termination • CANCEL Pending session cancellation • REGISTER Registration of user’s URL • OPTIONS Used to query options and capabilities • INFO Mid call signaling support • PRACK Provisional response acknowledgement • REFER Transfer user to a URL • SUBSCRIBE Request notification of event • NOTIFY Transport of subscribed event notification • MESSAGE Transport of instant message body • UPDATE To update session states

  14. SIP Response Codes • 1xx Informational • Request received, continuing to process the request. • 2xx Success • The action was successfully received, understood, and accepted. • 3xx Redirection • Further action needs to be taken in order to complete the request. • 4xx Client Error • The request contains bad syntax or cannot be fulfilled at this server. • 5xx Server Error • The server failed to fulfill an apparently valid request. • 6xx Global Failure • The request cannot be fulfilled at any server.

  15. SIP Message Headers and Bodies • Requests and Responses consist of multiple headers and values • Common headers present in all requests and responses • From logical call source • To logical call destination • Call-ID globally (time, space) unique call identifier • CSeq request sequence number within a call leg • Other headers present as needed (many) • Examples: • Contact indicates location of redirection • Via records route of SIP request, to route back response • Record-Route forces routing through a proxy for subsequent requests • Route forces routing for a request through a specified path • Content-Type specifies the Internet media type in message body • Content-Length indicates the number of octets in message body • SDP (Session Description Protocol) • Describes multimedia sessions • Carried as message body in SIP messages

  16. SIP Functions in 3GPP • User Agent • Application that sends and receives INVITE • Allocated to User Equipment (UE) • Proxy • Intermediary program that makes requests on behalf of other clients • Allocated to CSCFs • Registrar • Server that accepts REGISTER requests and updates location server • Allocated to S-CSCF • Location Service • To obtain information about a callee’s possible location(s) • Allocated to Home Subscriber Server (HSS) • Authentication and Authorization • To mutually authenticate the user and the network • Allocated to S-CSCF and Home Subscriber Server (HSS)

  17. TE MT GERAN TE MT UTRAN PS and IMS Network Architecture CSCF Multimedia IP Networks Mw SCP Mm HSS CSCF Mg Bearer Signaling Cx Gr MGCF BGCF Mr Gi EIR MRF Mc Gf Gi SGSN GGSN MGW Gi PSTN/ Legacy/External Iu IP MM Subsystem PS Domain

  18. IP Multimedia Traffic GPRS User Plane Protocols: IP Multimedia signaling and payload traffic Application Application Eg. IP, PPP Eg. IP, PPP PDCP PDCP GTP-U GTP-U External Network RLC RLC UDP/IP UDP/IP MAC MAC L2 L2 L1 L1 L1 L1 Mobile Radio Network (UTRAN) Core Network (GSN) Note: IP multimedia signaling and payload traffic are largely transparent to GPRS network, except for some inter-working functions in GGSN.

  19. IMS Network Connections S-CSCF P-CSCF I-CSCF Mobile GGSN Remote Access Point Remote Host IP Networks Remote Access Network GPRS Network HSS Gateway Application Servers Remote Host PSTN • Note: • Release 5 architecture • IP Multimedia signaling and payload are carried as GPRS user data. • New IP Multimedia session control functions are in orange boxes. • GGSN performs QoS translation between GPRS and IP domains.

  20. IMS Functional Entities • Home Subscriber Server (HSS) - extension of the HLR to include the data pertaining to the IP Multimedia Subsystem • Access from the CSCF will be based on IETF protocols (DIAMETER). • To the PS and CS domains, this entity will functionally be the HLR. • Call State Control Function (CSCF) - provides the call control functions : • Serving CSCF • SIP registrar, with cooperation from HSS which is location server • Session control call state machine for the registered end-point • Interaction with service platforms for service control, by providing service triggers • Proxy CSCF • SIP proxy server for the mobile, acting on behalf of UE within IMS • Forward messages between mobile and other SIP servers • Policy control function for QoS authorization • Interrogating CSCF • Allocate or determine the S-CSCF • May hide network topology.

  21. IMS Functional Interfaces HSS AS Cx Cx ISC Gm Mw Mw UE P-CSCF I-CSCF S-CSCF Mg Mg Mg BGCF MGCF Mc MGW

  22. IMS Service Control SIP Application Server Sh SIP Sh OSA API OSA Service OSA Cx SIP S-CSCF HSS Capability Server Application (SCS) Server SIP IM SSF MAP CAP CAMEL Service Environment

  23. Service Creation • Where to implement SIP service logic • SIP Servers (Application Server) in the network • Caller User Agent • Callee User Agent • SIP Programming Options • Call Processing Language (CPL) • SIP Common Gateway Interface (CGI) • SIP Servlets • OSA/Parlay.

  24. 3GPP2 – network plane

  25. 3GPP2 – SIP services plane

  26. 3GPP2 – MMD control/bearer

  27. Concerns with 3GPP IMS • Complex network architecture • Delayed time to market • More expensive equipment • Risk associated with unproven and complicated technologies • Tight-coupling between session and bearer controls • Network can be a bottleneck for introducing new services. • Ahead of 3GPP2 IP Multimedia standardization • Potentially negative marketing impact on CDMA2000.

  28. Standards Process • Develop 3GPP2 specifications based on 3GPP specifications • Alternative 1: Develop full 3GPP2 specifications based on 3GPP IMS specifications. • 3GPP2 maintains full control of its IMS specifications. • 3GPP2 needs to continuously monitor and match 3GPP standards changes in order to keep specifications in synch with, or similar to, 3GPP. • (Currently doing this.) • Alternative 2: Refer to 3GPP specifications for the access technology independent part of IMS, and develop only the access technology dependent part for 3GPP2. • 3GPP2 does not have control over the common part of IMS specifications. • 3GPP2 depends on 3GPP’s willingness to partition IMS specifications into access technology independent part and access technology dependent part. E.g. The common specifications of IMS should be independent from GPRS.

  29. AAA: Authentication, Authorization and Accounting AKA: Authentication and Key Agreement BGCF: Breakout Gateway Control Function CSCF: Call State Control Function GGSN: Gateway GPRS Service Node HSS: Home Subscriber Server I-CSCF: Interrogating CSCF IMS: IP Multimedia Subsystem MGCF: Media Gateway Control Function MGW: Media Gateway MMD: Multimedia Domain MRF: Media Resource Function MRFC: Media Resource Function Controller P-CSCF: Proxy CSCF QoS: Quality of Service S-CSCF: Serving CSCF SDP: Session Description Protocol SIP: Session Initiation Protocol UA: User Agent. Acronyms

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