H.323: Multimedia

Conferencing for Packet

Switched Networks

Dave LindberghManager, Technical Standards Group

PictureTel

Contents

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

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

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”

H.323 Components

Terminals Gatekeepers Gateways (H.323 to

H.320/H.324/POTS) MCUs

Multipoint Controller (MC) Multipoint Processor (MP)

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

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

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

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)

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)

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

H.225. 0

G.7xx H.26x

RTP

RTCP

Gate-keeper

Reg,Adm,Status(RAS)

Control Data Audio Video A/V Cntl Control

TCP UDP

IP

H.323 Protocol Stack

T.120 H.245

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)

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

Call Initiation

PictureTel

PictureTel

PictureTel

(1) ARQCan I call“Bob”?

(2a) GK resolves “Bob”to IP address through H.323registration or externalname service (e.g. DNS, ULS, etc..)(2b) Admission PolicyApplied(3) ACF

Yes, use thisIP Address

Bill Bob

GK

Call Connection

PictureTel

PictureTel

PictureTel

(4) SETUP (Create)

Bill Bob

GK

(5) ARQMay I answer?

(6) ACFYes

(7) ALERTING

(8) CONNECT (User answers)

H.245 Connection

PictureTel

PictureTel

PictureTel

Bill Bob

(9) H.245 connection established- Capability Exchange- Master/Slave Determination- Open Logical Channels

- audio, video

For this example, assume Bill wins the Master/Slave determinationand becomes the Multipoint Controller (MC) of the conference

Bill invites Ross

PictureTel

PictureTel

PictureTel

Ross

GK

(10) ARQInviteRoss (11) ACF

Resolved Ross’sIP Address

(12) SETUP (Invite)

(13) ARQMay IJoin?

(14) ACFYes

(15) ALERTING(16) CONNECT

(17) H.245 CONNECTION

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)

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

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

H.235 (“H.Secure”)

Privacy (encryption) A big issue on packet networks

Authentication Key Exchanges (RSA & DSS) Encryption per media stream Signaling procedures

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)

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

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

For More Information

Please visit the PictureTel Standards Page:

http://standards.pictel.com