SIP & H.323 Interworking

1. SIP & H.323 Interworking Name: Amir Zmora Title: PM Date: Feb 5 2003

2. Agenda • The Need for Interworking • SIP – H.323 Interworking • Types of Implementations • Optional Co-Locations • Summary • References

3. The Need for Interworking

4. A Bilingual VoIP World • H.323 • Large installation base • H.323 is still being developed and deployed • Enterprises are currently staying with H.323 • SIP • On carriers’ roadmap in addition to H.323 • Softswitches mostly support SIP • 3GPP has adopted SIP • Enhanced features (Presence, Instant Messaging) • The future of VoIP • SIP and H.323 will coexist for years to come therefore Interworking function (IWF) is required!

5. Situational Analysis: VoIP Developers’ Protocol Support Plans to Add Support H.323 - 50% SIP - 77% MGCP - 36% MEGACO - 53% • Miercom Survey - 96 VoIP vendors responded worldwide (8/2001)

6. SIP – H.323 Interworking

7. Open Issues • Synchronize with each protocol upgrade • Resolve unmapped message scenarios • Advanced call control handling • Overlap sending • Multiparty conferencing • Media switching • Handling SIP-H.323 security services • QoS exchange between protocols– OSP ? • Scalability– address resolution

8. Application Layer Application Layer SIP SDP Codecs RAS RTCP Codecs H.245 RTCP Q.931 RTP RTP TPKT TCP/UDP IP IP Layer The VoIP Protocols • VoIP Protocols Provide: Signaling, Media Control and Media Streaming • Many similar components, but… H.323 SIP

9. Main Mapped Functions • Registration • Address Resolution • Call Control • Call establishment and teardown • Supplementary Services • Out of band signaling (e.g. DTMF) • Media Control • Capabilities exchange • Multimedia channel handling • Multipoint conferencing • Media Streams Transport • Other Add-On Services • Presence, IM, etc.

10. Interworking issues • Call establishment • Getting more complex when H.323 is not using Fast Start • Address mapping • H.323 – Multiple addresses in alias list • Single address • Session description mapping • SDP Vs H.245 • More information on this can be found at end of presentation

11. Basic Call Scenario H.323 to SIP Setup(vipin@iwf.sip.com) INVITE Ringing Alerting OK Connect IWF H.323 Endpoint SIP User Agent H.245 May be included in Fast Start SDP Included in the INVITE RTP/RTCP Common protocol

12. Basic Call Scenario SIP to H.323 INVITE Setup(vipin@iwf.sip.com) Alerting Ringing Connect OK IWF SIP User Agent H.323 Endpoint H.245 May be included in Fast Start SDP Included in the INVITE RTP/RTCP Common protocol

13. Class 5 Features Mapping • H.323 and SIP address supplementary services differently • H.323 defines each feature specifically • SIP provides building blocks and call flows H.323 • Call Transfer • Call Diversion/Forwarding • Call Hold • Call Park and Pickup • Call Waiting • Message Waiting • Name Identification • Call Completion on Busy • Call Offer • Call Intrusion SIP • Call Transfer • Call Forwarding • Third-Party call control • Call Hold, Music on Hold • Single line extension • Incoming Call Screening • Outgoing Call Screening • Find-Me • Call Park & Pickup • Automatic Redial

14. Multiparty Conferencing H.323 Terminal SIP Terminal SGW SIP Terminal SIP Terminal MCU H.323 Terminal SIP Terminal H.323 Terminal H.323 Cloud SIP Cloud SGW SIP Terminal SGW H.323 Terminal H.323 Centralized/Decentralized Conferences SIP Full Meshed Conference

15. Types of Implementations

16. Gateway Types • Softswitch at the ITSP Edge • Signaling Gateway at the ITSP Edge • Signaling Gateway at the Enterprise Network Edge

17. Softswitch at the ITSP Edge Enterprise Enterprise Proxy Server Gatekeeper Softswitch H.323 SIP ITSP IP Network Gateway SCN Gateway

18. Softswitch at the ITSP Edge • At the network edge • Focuses on bridging IP and PSTN • Delivers mostly add-on services • Very complex • Must be carrier-grade • High capacity • Highly redundant • Expensive!

19. Enterprise H.323 Gatekeeper H.323 Signaling Gateway SIP Proxy SIP Softswitch SIP Gateway ITSP IP Network Gateway Signaling Gateway at the ITSP Edge SCN

20. Signaling Gateway on the ITSP Edge • On the network edge • Focuses on “simple” H.323-SIP bridging • No add-on services • Simple functionality • Must be carrier-grade • High capacity • Highly redundant • Relatively inexpensive

21. Signaling Gateway on the Enterprise Network Edge SIP Proxy Gatekeeper SIP Signaling Gateway H.323 Enterprise SIP Proxy Gateway SIP Softswitch SIP Gateway ITSP IP Network SCN Gateway

22. Signaling Gateway at the Enterprise Network Edge • At the network edge • Focus on “simple” H.323-SIP bridging • No add-on services • Simple functionality • Does not need to be carrier grade • Inexpensive

23. Address Resolution Optional Co-Locations

24. SIP - H.323 Signaling Gateway RRQ REG RRQ SIP Proxy/ Registrar H.323 Terminal SIP UA Gatekeeper LRQ Within SIP Proxy • SIP Calls • Register with SIP Proxy • SIP Proxy forwards UA Registrations to Gatekeeper via SG • H.323 Calls • Regular RAS scenario

25. SIP - H.323 Signaling Gateway REG SIP Proxy/ Registrar REG SIP UA Gatekeeper RRQ H.323 Terminal Within Gatekeeper • SIP Calls • Similar to regular SIP Calls • H.323 Calls • RAS • Forward to proper SIP Registrar/Proxy

26. As An Independent Entity RRQ REG SIP Proxy/ Registrar H.323 Terminal Gatekeeper SIP UA RRQ REG SIP - H.323 Signaling Gateway • SIP Calls • Register with SIP Proxy • When call reaches the signaling gateway it queries the H.323 network • H.323 Calls • Register with Gatekeeper • When call reaches the signaling gateway it queries the SIP network

27. All-In-One RRQ REG SIP Proxy/ Registrar H.323 Terminal SIP UA Gatekeeper SIP - H.323 Signaling Gateway • SIP Calls • Register with SIP Proxy • H.323 Calls • Register with Gatekeeper • Signaling Gateway • Use both for address resolution

28. Conclusion

29. Summary • We are in a multi-protocol world therefore both SIP and H.323 should be supported • Increased complexity of H.323 and SIP create interworking and interoperability challenges • Advanced call services – complex/open issue

30. References

31. References of Interworking Standards • IETF SIP-H.323 Interworking draft “draft-agrawal-sip-h323-interworking-reqs-03.txt” • Links: • www.radvision.com • www.h323forum.org • www.sipforum.org • My mail: amirz@radvision.com

32. Interworking Issues

33. Call Establishment • SIP INVITE / H.323 Fast Start • Signaling Destination Address • Local and Remote Media Capabilities • Local and Remote Media Addresses • Regular H.323 Setup • Stage-1: Signaling Destination Address • Stage-2: Local and Remote Media Capabilities • Stage-3: Local and Remote Media Addresses

34. Address Mapping Issues - 1 • H.323 uses several ASN.1 fields while SIP uses URI only • SIP URI to H.323 address is simple • H.323 address to SIP might be complicated • Address Translation Example SIP To H.323 “sip:+1-201-529-1212:1234@bridge.com;user=phone” Mapped in H.323 to->H.323 Address: { e164 = "12015291212", h323-ID = "sip:+1-201-529-1212:1234@bridge.com", url-ID = "sip:+1-201-529-1212:1234@bridge.com", email-ID= "+1-201-529-1212:1234@bridge.com" }

35. Address Mapping Issues - 2 • H.323 to SIP Address Translation Example H.323 E164: “12015291212”  “sip:+1-201-529-1212@host;user=phone” H.323 H323Id: “mailto:user@domain”  “sip:user@domain” • SIP and H.323 ENUM Support • Phone# 480-990-1101 URL “1.0.1.1.0.9.9.0.8.4.e164.arpa”

36. Session Description Mapping - 1 • H.245 • Very comprehensive protocol • Covers many control issues (e.g. Chair Control) • SDP • Is a media description language • Relatively limited • Lack of cross-media, inter-media constraints

37. Session Description Mapping - 2 • Mapping • SDP to H.245 • SDP message can easily be mapped to H.245 • Straightforward • H.245 to SDP • H.245 message to one or more SDP messages • Can be complicated or impossible under certain circumstances

38. Thank You www.radvision.com amirz@radvision.com