SIP-H.323 Interworking Requirements

1. SIP-H.323 Interworking Requirements draft-agrawal-sip-h323-interworking-reqs-00.txt Hemant Agrawal - GlobeSpan Inc, Radhika R. Roy - AT&T, Vipin Palawat - Opuswave Networks Inc, Alan Johnston - MCI WorldCom, Charles Agboh - Global TeleSystem Group, David Wang - Nuera Communications Inc, Kundan Singh and Henning Schulzrinne - Columbia University IETF-48

2. Content • Roadmap for SIP-H.323 Interworking - VG #3 • Architecture and Functionalities - VG #4 • General Interworking Requirements • Pre-Call Requirements - VG #5 • Basic Call Requirements- VG #6 • Transport Requirements - VG #7 • State Machine Requirements - VG #8 • Service Interoperability Requirements - VG #9 • Security Requirements - VG #10 • Activities Planned for Next Phase - VG #11 IETF-48

3. Roadmap for SIP-H.323 Interworking • SIP-H.323 Interworking Requirement RFC • Requirement draft (draft-agrawal-sip-h323-interworking-reqs-00.txt) • Two phases of the interworking standard • Phase 1: Basic call establishment and termination RFC • Phase 2: Optional, advanced features, and services RFC • Both phases have to meet the general requirements • Specified in the requirement document (draft-agrawal-sip-h323-interworking-reqs-00.txt) IETF-48

4. Architecture and Functionalities • Interworking function (IWF) will allow the interworking between the SIP and H.323 networks • Architecture • Can be architected in a variety of ways • Co-existence with H.323 gatekeeper (GK) and/or SIP server, or stand-alone • Location of IWF is a matter of implementation, not a protocol issue • Interworking solution shall work for a minimum configuration required for the mandatory features of both H.323 and SIP • Functionalities • Call sequence mapping, Address resolution, Terminal Capability transactions, Opening and closing of media channels, Mapping media algorithms for H.323 and SIP network, Call resource reservation and release, Ability to provide the state of a call, Call state machine, Mid Call signal processing, and Service Interoperability Logic • No processing of media data IETF-48

5. General Interworking RequirementsPre-Call Requirements • General • May have a table of reference for lookup to resolve H.323 and SIP addresses to IP addresses • May use the capabilities of either H.323 GK or SIP server • May keep the address resolution information to itself if H.323 GKs or SIP servers not available • Registration with H.323 Gatekeeper • Can register with only one GK to provide information about SIP side extension to the GK • Registration with more that one GK is for further study • SIP user agent (UA) may register with the GK via the IWF • Creates an H.323 alias address for the SIP UA and binds its own transport address to the alias address • Registration with SIP Server • Can register itself with the SIP server using TRIP to provide information about H.323 side extension to the SIP server • How an IWF can register directly with one or many SIP servers is for further study IETF-48

6. General Interworking RequirementsBasic Call Requirements • Shall use all mandatory features of H.323 version 2.0 and SIP version 2.0 (RFC-2543) • Basic call requirements • Provide default settings and release any call related resources on the direction of the call deactivation • Address resolution for all addressing schemes of H.323 and SIP • Capability negotiation • No assumption about the capabilities of either SIP UA or H.323 terminal; may indicate a default capability; default capability follows the mandatory capability requirements • Shall send the best possible way all the capability descriptors (e.g., H.245 for H.323, SDP for SIP) to each other • Support opening and closing of logical channels unidirectional, symmetric bi-directional, and asymmetric bi-directional opening of channels as needed • Shall support for H.323 fast connect procedures, H.245 tunneling, pre-granted ARQ • Shall support of overlapped sending IETF-48

7. Transport Requirements • Shall support both reliable (e.g., TCP) and non-reliable (e.g., UDP) transport for delivery of messages • Shall not provide priority of signaling messages over other messages • Support of H.323 signaling over UDP is optional • Network does not assure quality-of-service (QOS) • SIP and H.323 network can be anywhere • Media transport requirements • RTP is used for carrying media by both H.323 and SIP network • If not, a media gateway is required • Support for large fan-out IETF-48

8. State Machine Requirements • Treatment of messages • Unexpected messages as “error” messages • Messages that do not change state as “Non-triggering or Informational” messages • Messages that are expected to change states as “Triggering” messages • Provide guidelines that classify all possible messages into above three categories • Specify actions that to be taken on the content of the messages in the state machine IETF-48

9. Service Interoperability Requirements • Define scenarios and application priorities from a service provider’s point of view • Resulting solution to be used in a globally deployable network that accommodates both SIP and H.323 IETF-48

10. Security Requirements • Enable a simple security scheme • Accept requests only from SIP EPs, SIP servers, H.323 EPs, or H.323 GKs • Reject all requests other than the SIP or H.323 entities • All EPs trying to use the IWF for calls or other purpose needs to be authorized by SIP servers or H.323 GKs as appropriate, if present • Need to prevent denial of service security attacks • Maintain persistent data for authorized endpoints for future verifications IETF-48

11. Activities Planned for Next Phase • Call supplementary services like call forwarding, call hold, and call transfer; Extensions of H.245 and SDP for ATM and other transport; trunking between SIP/H.323 networks; registration with multiple GKs/SIP servers; Support of early H.245 in H.323 by the IWF; Sovereignty over the IWF • Audio and video conferencing; Session change (re-invite, mode request) • QOS signaling ; Security - authentication, authorization and privacy; Billing • Network management; Redundancy; Support for clearing house • The algorithm and list of messages for finding out the maximum mapping of capability descriptors with corresponding SDP by the IWF IETF-48