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IP Core Networks Standards and Next Steps

IP Core Networks Standards and Next Steps. February 2003 Jack Nasielski. Outline. IP Multimedia Standardization in 3GPP and 3GPP2 3GPP IP Multimedia Subsystem (IMS) 3GPP2 IP Multimedia Domain (MMD) End-to-end signaling and media transport over IP

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IP Core Networks Standards and Next Steps

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  1. IP Core NetworksStandards and Next Steps February 2003 Jack Nasielski

  2. Outline • IP Multimedia Standardization in 3GPP and 3GPP2 • 3GPP IP Multimedia Subsystem (IMS) • 3GPP2 IP Multimedia Domain (MMD) • End-to-end signaling and media transport over IP • Call/Session control using IETF Session Initiation Protocol • Internet Multimedia Protocols • Services • Standards Architecture • Next Steps • Concerns and considerations with IMS • Is this a priority for operators?

  3. IP Core Network Standards • Original goals included: • Operator cost saving (CAPEX & OPEX) • Independence of wireless access technology • Flexibility in service creation • Integrated multimedia services over IP • 3GPP IP Multimedia Subsystem (IMS) • Declared functionally complete in June 2002 as part of Release 5 • The specs are still not stable • Call control based on IETF SIP (Session Initiation Protocol) • Release 5 focused on signaling capability instead of services; no significant service is yet defined; possible services are Voice and Video over IP • 3GPP2 IP Multimedia Domain (MMD) • Includes 3GPP IMS as a subset • Re-using 3GPP text for easier interop and roaming between systems • Strong influence on IETF SIP standardization.

  4. 3GPP2 IP Multimedia Domain (MMD) • 3GPP2 All-IP Adhoc group: • Formed in early 2000, shortly after the 3GPP All-IP workshop • Similar goals as 3GPP IMS • Currently balloting some parts under project X.P0013 • (note TSG-N and TSG-P recently merged to TSG-X, partly to better handle this project.) • Very similar to 3GPP, changes for: • IPv4 in addition to IPv6 • Optional R-UIM (Subscription storage on MS) • Different packet data access technologies; 3GPP2 packet data services versus GPRS • IMS interaction with Mobile IP • Legacy MS Domain (VoIP in the core, CDMA at the edge) • Security and QoS procedures still in debate.

  5. 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) • 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.

  6. Example Services Enabled by SIP • Value-added telephony 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)

  7. TE MT GERAN TE MT UTRAN 3GPP PS and IMS 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

  8. 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.

  9. 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

  10. 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.

  11. 3GPP2 – network plane

  12. 3GPP2 – SIP services plane

  13. 3GPP2 – MMD control/bearer

  14. 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.

  15. 3GPP2 Considerations • Non-real-time (e.g. Presence/IM) and near-real-time (e.g. streaming) services can be deployed over existing CDMA2000 data networks with IMS/MMD architecture. • CDMA2000 packet data network is feasible to support real-time multimedia (voice and video over IP), but improvements are needed for better real-time service quality: • QoS support • Payload header compression • SIP signaling compression.

  16. Standards Process • Currently developing 3GPP2 specifications based on 3GPP Release 5 specifications • For straightforward interoperability and roaming with 3GPP. • For next release, hope to refer to access technology independent part of IMS • allows IMS to work with non-3GPP access technologies such as cdma2000 and WLAN. • 3GPP Release 6 includes some services: Presence/IM.

  17. Discussion • What do CDMA operators want? • When? • Priorities?

  18. 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. Appendix – acronyms and SIP info

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

  20. 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.

  21. 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.

  22. 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

  23. 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.

  24. 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 • Via records route of SIP request, for routing the response • Other headers present as needed (many) • Examples: • Contact indicates location of redirection • 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

  25. SIP Functions • 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)

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