H.323: Multimedia Conferencing for Packet Switched Networks

1. H.323: Multimedia Conferencing for Packet Switched Networks Dave Lindbergh Manager, Technical Standards Group PictureTel

2. Contents • What is H.323? • H.323 Components • Protocol Stack • Call Setup • Current H.323 Standards Work

3. What is H.323? • ITU-T standard for multimedia videoconferencing on packet-switched networks • LANs and corporate intranets • Internet (limited by Internet performance) • Basis for IMTC VoIP Internet Telephony • On LAN, typical video call uses 100-300 kbit/s of LAN capacity • LAN traffic can be managed and controlled

4. History of H.323 • May 1995 - H.323 work started • June 1996 - Decided by ITU-T • January 1998 - Version 2 planned for ITU-T approval (added functions) • ITU is learning to work on “Internet time”

5. H.323 Components • Terminals • Gatekeepers • Gateways (H.323 to H.320/H.324/POTS) • MCUs • Multipoint Controller (MC) • Multipoint Processor (MP)

6. H.323 Terminal • Two Versions • Corporate Network (high quality) • Internet (optimized for low bandwidth 28.8/33.6 - G.723.1 and H.263) • Built in Multipoint capability for Ad Hoc conferences • Multicast (multi-unicast) allows 3-4 people in call without centralized mixing or switching

7. H.323 Gatekeeper • Address Translation • H.323 Alias to transport (IP) address based on terminal registration • “email-like” names possible • “phone number like” names possible • Admission control • Permission to complete call • Can apply bandwidth limits • Method to control LAN traffic

8. Gatekeeper Functions (cont.) • Management of gateway • H.320, H.324, POTS, etc. • Call Signaling • May route calls in order to provide supplementary services or to provide Multipoint Controller functionality • Call Management/Reporting/Logging

9. H.323 Gateways • Provide world wide connectivity and interoperability from LAN • H.320, H.324, regular POTS telephones • Map Call Signaling (Q.931 to H.225.0) • Map Control (H.242/H.243 to H.245) • Media Mapping (FEC, multiplex, rate matching, audio transcoding, T.123 translation)

10. Multipoint: MC+MP • MC - Multipoint Controller portion of a traditional MCU • Manage common modes, capabilities • MP - Multipoint Processor • Portion of traditional MCU mixing or switching audio. Not necessarily co-resident with MC. (e.g. MC running multicast conference with each terminal mixing audio)

11. MCU Functions • Media Distribution • Unicast - send media to one terminal (centralized in MP; traditional model) • Multicast - send to each receiver directly • Hybrid - some of each • Manage Ad Hoc multipoint calls • Join, invite, control of conference modes • Traditional MCU applications • Multiprotocol via Gateways

12. H.323 Protocol Stack Control Data Audio Video A/V Cntl Control Gate- keeper Reg, Adm, Status (RAS) G.7xx H.26x RTCP H.225. 0 H.245 T.120 RTP TCP UDP IP

13. H.323 Protocol Components • H.323 - System Document • H.225.0 - Call Signaling, Packetization • Gatekeeper Registration, Admission, and Status • H.245 - Control (also used in H.324, H.310) • T.120 - Data and Conference Control • RTP - Real-time Transport Protocol (IETF) • RTCP - Real-time Transport Control Protocol (IETF)

14. Call Setup A Call Setup Example • a point to point call • 3rd terminal invited into call (Ad hoc multipoint) • One Gatekeeper using the Direct Call Model

15. PictureTel Call Initiation GK (2a) GK resolves “Bob” to IP address through H.323 registration or external name service (e.g. DNS, ULS, etc..) (2b) Admission Policy Applied (1) ARQ Can I call “Bob”? (3) ACF Yes, use this IP Address Bob Bill

16. PictureTel Call Connection GK (5) ARQ May I answer? (6) ACF Yes (4) SETUP (Create) (7) ALERTING (8) CONNECT (User answers) Bob Bill

17. PictureTel H.245 Connection (9) H.245 connection established - Capability Exchange - Master/Slave Determination Bob Bill - Open Logical Channels - audio, video For this example, assume Bill wins the Master/Slave determination and becomes the Multipoint Controller (MC) of the conference

18. PictureTel Bill invites Ross GK (13) ARQ May I Join? (10) ARQ Invite Ross (11) ACF Resolved Ross’s IP Address (14) ACF Yes (12) SETUP (Invite) (15) ALERTING (16) CONNECT Ross (17) H.245 CONNECTION

19. Work in progress • H.323 • Implementors Guide • Version 2 • Supplementary Services • H.225.0 • Version 2 • Annex E - Video Packetization (w/IETF) • Annex F - Audio Packetization (w/IETF)

20. Work In Progress (Continued) • H.245 Version 3 • To support H.323 version 2 • H.246 (“H.Interworking”) - Gateway • Annex A.1 - H.323-H.320 • Annex A.2 - H.323-H.324 • H.235 (“H.Secure”) - Encryption • H.332 (“H.Loosely Coupled”) - Broadcast • H.MediaMIB

21. H.323/H.225.0 Version 2 • Enhanced procedural descriptions • Gateway registration and selection procedures, registration capabilities • Authentication and Security • MC Cascading and transfer of MC • Relationship to T.120 and T.130 • RAS Retry/Time-out • Additional audio and video packetizations

22. H.235 (“H.Secure”) • Privacy (encryption) • A big issue on packet networks • Authentication • Key Exchanges (RSA & DSS) • Encryption per media stream • Signaling procedures

23. H.246 (“H.Interworking”) • “Interworking of H-Series of Multimedia Terminals” - Standard for gateways • Interworking between H.323, H.320, H.324, H.310, regular POTS telephones • Initial Focus: • H.323 to H.320 (Annex A.1) • H.323 to H.324 (Annex A.2)

24. H.332 (“H.Loose Multipoint”) • “Loosely coupled” multipoint conferences • Potentially thousands of participants • Primarily broadcast • Procedures for one to many or panel type conferences • Similar to H.331(for H.320): • No capability exchange in conference

25. H.MediaMIB • Management Information Database (MIB) definitions for H.323 entities (terminals, Gatekeepers, Gateways, and MCUs) • Possible MIB definitions for other H.series endpoints • IETF coordination required

26. For More Information • Please visit the PictureTel Standards Page: • http://standards.pictel.com