Common IMS in TISPAN

1. Common IMS in TISPAN SA3LITISPANWG7_08_02 Scott CADZOW

2. IMS in NGN • NGN brings together many access technologies to a common service enabling platform • IMS serves as the common service enabling platform • Access technologies are managed in their own abstraction layer • NASS (Network Access Sub-System) • QoS and access privileges are managed through an additional abstraction layer • RACS (Resource and Admission Control System) • Users may use many access technologies to access services and may use them concurrently or sequentially within a single session • This requires IMS to be supportive of any NASS or RACS technology • Has to ensure that NASS/RACS requirements are devolved to the correct layer

3. The goals for NGN LI standardisation • Conformance to International User Requirement • As annex to COM 96/C329/01: "European Union Council Resolution COM 96/C329/01 of 17 January 1995 on the Lawful Interception of Telecommunications" • As found in TS 101 331 "Telecommunications security; Lawful Interception (LI); Requirements of Law Enforcement Agencies“ • Compliance with objectives of ECN&S regulatory framework • The NGN consists of many ECN and many ECS with loose relationships • Clear identification of Points of Interception • What is available at different PoI • Correlation between different PoI • Prevention of duplication of invocation of interception at PoIs

4. Documents to integrate • TISPAN • TS 187 005, in draft for NGN-R2 • 3GPP SA3-LI • 33.107, stage 2 in draft for R8 • 33.108, stage 3 in draft for R8 • TC LI • TS 102 232, handover to IP networks • ES 201 671/TS 101 671, handover to Circuit Switched networks

5. Technologies supported by the NGN • Separation of ECN and ECS • ECS technologies: • IMS (care of 3GPP) • PES (ISDN/PSTN on soft-switches) • IPTV • Corporate services • ECN technologies: • ADSL • PLMN Radio (care of 3GPP) • LAN radio (mostly care of 3GPP) • PSTN/ISDN

6. Interception in the NGN - identity • ECS identity • MSISDN • E.164 • SIP-url (sip-user@sip-domain) • Other … • ECN identity • IMSI • Chap credential and identity

7. Interception in the NGN - signalling • ECS • IMS (SIP) signalling • REGISTER (equivalent to MAP, found at HLR/VLR like entities) • INVITE, ACK, BYE, CANCEL, OPTIONS (found at CSCF entities) • PES/PSS • ISDN emulation signalling found at Signalling gateways (H.248) • SIGTRAN, SIP-I • ECN • Access signalling (no service), CHAP, PPP etc.

8. Interception in the NGN - content • ECS • No traffic content • Some extended signalling content in SDP/SIP • ECN • IP traffic content • TCP, UDP, RTP • Non-IP traffic content

9. Problems in NGN, ECN&S interception • Correlation across ECN/ECS boundary • IMS into NASS via RACS (Gq’) for QoS transport control • Resource requests from ECS to ECN not personalised • Dynamic assignment of NASS and RACS without IMS intervention • One service many transport offerings • Ownership break across ECN/ECS boundary (one CSP for each of ECN and ECS) • No correlation as there is no common visibility to CSP

10. IMS interception • IMS is an instance of ECS technology • Independent of ECN technologies • IMS is a platform • No services per-se • Expectation from NGN • Clear identification of PoI for various IMS capabilities • Common capability for all IMS implementations

11. Concerns to be addressed • Structure of IMS interception • One clause for any technology (IMS is an ECS technology and any ECN technology can/should be able to access it) • Reference from TS 187 005 to 33.107 • Annex showing normative application from TS 187 005 to 33.108 • Timetable for IMS interception • Required for NGN-R2 • TS 187 005 to be finalised very soon and needs to have IMS interception included • Ideally by reference to 33.107 and 33.108 • If not by reference then in a transferable way (i.e. defined in TISPAN for movement to 33.107 and 33.108 when appropriate)