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A Conference Gateway Supporting Interoperability Between SIP and H.323

A Conference Gateway Supporting Interoperability Between SIP and H.323. Jiann-Min Ho (Presenter) Jia-Cheng Hu Information Networking Institute Peter Steenkiste School of Computer Science Dept. of Electrical and Computer Engineering Carnegie Mellon University. Agenda. Overview

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A Conference Gateway Supporting Interoperability Between SIP and H.323

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  1. A Conference Gateway Supporting Interoperability Between SIP and H.323 Jiann-Min Ho (Presenter) Jia-Cheng Hu Information Networking Institute Peter Steenkiste School of Computer Science Dept. of Electrical and Computer Engineering Carnegie Mellon University

  2. Agenda • Overview • Target network and goal • Signaling protocols and comparison • Design • Implementation • Performance evaluation • Discussion • Related work • Conclusion

  3. Overview -Multi-party Media Conference • Media conference application drivers • Network bandwidth and endpoint capability • Signaling and media streaming protocols • Signaling protocols: • H.323 (ITU-T) vs. SIP (IETF) • Media transport protocol: RTP (RFC1889)

  4. Target Network and Goal • Target network – • Packet switching network (e.g. IP), not PSTN • Future network infrastructure • Goal – two folds • Build a practical system allowing SIP and H.323 clients to participate in one video conferencing session. • A set of recommendations and for developers and standard bodies that would improve interoperability issues.

  5. Signal Protocols -Generic H.323 Call Flow

  6. Signal Protocols -Generic SIP Call Flow

  7. Signal Protocols -Comparison of H.323 and SIP • Modularity • Synchronization of the mapping procedures during operation • Message presentation • Translation of syntax • Mapping of an H.323 conference and a SIP session • Map H.323 conference ID and SIP session ID • Map the H.245 capabilityDescriptor structure to SDP syntax

  8. Signal Protocols -Comparison of H.323 and SIP(cont.) • Advertising • Conference information availability • Determination of conference media capability Applicable solution: • Central determination via an intermediate agent serving as an H.323 mc • Control over membership • Generic admission control mechanisms and strategies handling conference membership

  9. Design – GCCG Functionality

  10. Design - Functionality of GCCG in SIP and H.323 perspective • On the H.323 side • Gatekeeper (GK), Multipoint Controller (MC) and Multipoint Processor (MP) without transcoding • Independent conferencing components • On the SIP side • Proxy Server and Conferencing Server

  11. Design – Key Design Decisions • Conference Call Messages Translation H.323  SIP • Conference Create - • H.225 SETUP (? H.245 CapSet )  SDP message • N/A (no SAP supported)  SDP message • Conference Invite - depend on conferencing scenarios • H.225 SETUP INVITE (? SDP) message (? FastStart) + OPTION(obtain/check SIP invitee Media Cap. - Invitable?) • H.225 SETUP  INVITE (SDP) message • Conference Join - • H.225 SETUP  N/A (trigger IGMP message) • N/A  N/A (only IGMP message)

  12. Design – Key Design Decisions(Cont.) • Central Determination of Conference Media Capability • Ongoing Conference Information • Conference Management: Membership Control and Session Management

  13. Design – Example: Conference Invite and Join • H.323 Client Invites SIP Client via Fast Connection Procedure • NOTE: Conference is created after the invitee’s media cap is received.

  14. Design – Example: Conference Invite and Join (Cont.) • A H.323 Endpoint joins an ongoing conference.

  15. Implementation GCCG Internal Architecture

  16. Implementation –Operation and Status • Only video is available. • Simple Conference Media Mode Determination • H.323 clients are lack of conference information, LDAP is not supported. • Media streams (RTP) are forwarded via GCCG; no support from media mixing/transcoding components/gateways.

  17. Performance Evaluation • Correctness of conferencing signaling flow via GCCG • Testbed configuration • One GCCG Server (Linux PC) and Five PC Clients (NT) • Video Conferencing Software • MS NetMeeting version 3.01 and the MBone tools SDR v2.9 and VIC v2.8. • Common communication mode - H.261 • Network Configuration • 10 Mbs shared Ethernet

  18. Performance Evaluation (cont.)

  19. Performance Evaluation (cont.) Comparison of Average RTT

  20. Discussion • Negotiation of Media Capabilities • Common conference media type (no transcoding GW) • H.323 – determined by MC via H.245 procedures • SIP – use a proxy server to query media capability information. OPTION message can be applied. Standard? Draft? • Translation of message syntax between H.245 and SDP • Change of media stream codec gracefully?

  21. Discussion (cont.) • Session Advertising • Conference information advertisement • SIP – operate with SAP (push) • H.323 – LDAP can be used (pull) if clients require this feature • Conference information mapping • Adaptation of Call Signaling Semantics • Reduce signaling overhead via H.323 FastConnect • Conference Control • H.323 – ITU-T T series, e.g. T.124, GCCP… • SIP – drafting, standards?

  22. Discussion (cont.) • IP Multicast • Characteristic of the architecture – open conference • Authorization, authentication, encryption • Application level support – conference server (GCCG) and clients (H.323/SIP) • IP multicast support – match application needs • Access media streaming multicast address • H.323 – determined by MC • SIP – from SAP messages • malloc

  23. Related Work • Several active groups, e.g. aHIT! from IMTC, ITU-T SG 16 and TIPHON, and … • H.323/SIP signaling gateway • - Columbia University • Our prototype implementation focus • Multi-party media conferencing signaling support • IP multicast efficiency

  24. Conclusion • Completion of interoperability for H323 and SIP in multiparty media conferencing sessions • Recommendation for raised interoperability issues.

  25. Q & A

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