Interworking Between SIP/SDP and H.323

1. Agenda Compare SIP/H.323 Problems in interworking Possible solutions Conclusion Q/A Interworking Between SIP/SDP and H.323 Kundan N. Singh, Dept. of Computer Science, Columbia University kns10@cs.columbia.edu Kundan Singh/SIP-H.323

2. What is H.323 ? Multimedia Communication Protocol Terminal/ User Agent Terminal/ User Agent Gatekeeper Q931 H245 RTP RAS H450 MCU (Conferencing) Gateway (Bridge to another network) H323 Box H323 Network Kundan Singh/SIP-H.323

3. What is SIP ? Session Initiation Protocol for Internet Registrar Redirect Proxy Servers UserAgent UAS/UAC Kundan Singh/SIP-H.323

4. H.323 vs SIP Typical UserAgent Protocol stack for Internet Terminal Control/Devices Terminal Control/Devices H.245 RTCP Q.931 RAS RTCP SIP SDP Codecs Codecs RTP RTP TPKT TCP UDP Transport Layer IP and lower layers Kundan Singh/SIP-H.323

5. SIP vs H.323 • Binary ASN.1 PER encoding • Sub-protocols: H.245, H.225 (Q.931, RAS, RTP/RTCP), H.450.x... • H.323 Gatekeeper • Text based request response • SDP (media types and media transport address) • Server roles: registrar, proxy, redirect Both use RTP/RTCP over UDP/IP Kundan Singh/SIP-H.323

6. Interworking ProblemsCall setup translation H.323 SIP Q.931 SETUP INVITE Destination address (Bob@office.com) Q.931 CONNECT 200 OK Terminal Capabilities Media capabilities (audio/video) Terminal Capabilities ACK Open Logical Channel Media transport address (RTP/RTCP receive) Open Logical Channel • Multi-stage dialing • H.323v2 Fast-start is optional Kundan Singh/SIP-H.323

7. H.323 Gatekeeper SIP registrar H.323terminal SIP user agent Interworking ProblemsUser Registration ? H.323 SIP Alias: Henry E164: 7040 sip:sam@home.com sip:7063@gateway.com • Location independent user identifier ? • Use information from both networks Kundan Singh/SIP-H.323

8. Interworking ProblemsMedia Description SIP/SDP (dynamically choose from listed modes) List of alternative set of algorithms. audio G.711 Mu law, G.723.1, G.728 video H.261 H.323/H.245 (declare your exact modes) Supports inter-media constraints { [G.711 Mu law, G.711 A law][H.261 video]} { [G.723.1] [no video] } • Translation in both directions • Algorithm selection by end-systems Kundan Singh/SIP-H.323

9. Interworking ProblemsCall Services • H.323 Conferencing: centralized signaling control, MC (Multi-point Controller) • Supplementary services, like call transfer: H.450.x • SIP Conferencing: centralized bridged + decentralized distributed • REFER, 3pcc Kundan Singh/SIP-H.323

10. Interworking ProblemsSecurity and QoS • H.323 uses H.235, whereas SIP uses Basic, Digest, PGP • Media Traffic end-to-end; QoS ? Kundan Singh/SIP-H.323

11. What we want ? • Transparent translation • Minimum modification in SIP or H.323 • Use features from both SIP and H.323 • Direct RTP/RTCP traffic; end-to-end Kundan Singh/SIP-H.323

12. H.323 Gatekeeper + SGW pc1.office.com SIP registrar server H.323 terminal 128.59.19.200 SIP user agent User registrationRegistration info to foreign network REGISTER henry@office.com Contact:pc1 home.com INVITE henry@office.com 3xx Moved Contact:pc1 RRQ henry@office.com Contact:128.59.19.200 sam@home.com use SIP REGISTER and/or H.323 RRQ/RCF Kundan Singh/SIP-H.323

13. SIP registrar server + SGW H.323 Gatekeeper pc1.office.com H.323 terminal 128.59.19.200 SIP user agent User registrationRegistration info from foreign network LRQ/LCF home.com INVITE henry@office.com 200 OK RRQ henry@office.com Contact:128.59.19.200 sam@home.com use SIP OPTIONS and/or H.323 LRQ/LCF Kundan Singh/SIP-H.323

14. User registrationDifferent Architectures • SGW co-located with H.323 gatekeeper • SGW co-located with SIP registrar/proxy server • Independent SGW Kundan Singh/SIP-H.323

15. 200 OK. ACK RTP/RTCP Call Setupwith H.323v2 Fast Start (Almost) One-to-one mapping between SIP and H.323 messages. H323 SIP Setup/FastStart INVITE Connect/FastStart Reverse direction is similar Kundan Singh/SIP-H.323

16. Call Setupwithout Fast Start H.323 SIP Q.931 SETUP INVITE Destination address (Bob@office.com) Q.931 CONNECT 200 OK Terminal Capabilities Media capabilities (audio/video) Terminal Capabilities ACK Open Logical Channel Media transport address (RTP/RTCP receive) Open Logical Channel Accept the call from H.323, forward to SIP after OLC ? Not desirable. Kundan Singh/SIP-H.323

17. Acknowledgement Acknowledgement RTP/RTCP Call Setupwithout Fast Start, SIP to H.323 H323 SIP Setup/Q931 INVITE Signaling Gateway Connect/Q931 Capabilities/H245 Capabilities/H245. Media Transport Address 200 OK. Open Logical Channel/ H245 ACK Open Logical Channel / H245 Kundan Singh/SIP-H.323

18. Acknowledgement Acknowledgement Open Logical Channel RTP/RTCP Call Setupwithout Fast Start, H.323 to SIP H323 SIP Setup/Q931 INVITE Signaling Gateway Connect/Q931 200 OK ACK Capability Exchange Media Transport Address Open Logical Channel Re-INVITE/SIP+SDP Kundan Singh/SIP-H.323

19. Media Capability • Modify SIP/SDP : multiple capability sets, or... • Let the SGW choose a sub-set of capabilities for SIP side • Re-INVITE or change in H.323 mode or logical channels, whenever it changes Kundan Singh/SIP-H.323

20. ConclusionWhat can be done ? What can’t ? • Basic audio/video call • Transparency of User registration • Advanced calls with complex sessions • Conferencing • SIP centered, H.323 centered • Other supplementary services • . . . Kundan Singh/SIP-H.323

21. ConclusionStatus • IETF mailing list “sip-h323@egroups.com”. Finalizing requirements document • IMTC and ETSI TIPHON • Convergence between SIP and H.323 in newer versions Kundan Singh/SIP-H.323

22. ConclusionImplementation - sip323 • Prototype (free download) system at http://www.cs.columbia.edu/~kns10/software/sip323 • Other information at http://www.cs.columbia.edu/~kns10/research/gw • My contact info: kns10@cs.columbia.edu Kundan Singh/SIP-H.323