1
Scope
2
Normative references
3
Definitions
4
Symbols and abbreviations
5
Conventions
6
System description
6.1 Information streams
6.2 Terminal characteristics
6.2.1 Terminal elements outside the scope of
this Recommendation
6.2.2 Terminal elements within the scope of
this Recommendation
6.2.3 Packet based network interface
6.2.4 Video codec
6.2.5
Audio codec
6.2.6 Receive path delay
6.2.7 Data channel
6.2.8 H.245 control function
6.2.9 RAS signalling function
6.2.10 Call signalling function
6.2.11 H.225.0 layer
6.3 Gateway characteristics
6.4 Gatekeeper characteristics
6.5 Multipoint controller characteristics
6.6 Multipoint processor characteristics
6.7 Multipoint control unit characteristics
6.8 Multipoint capability
6.8.1 Centralized multipoint capability
6.8.2 Decentralized multipoint capability
6.8.3 Hybrid multipoint-centralized audio
6.8.4 Hybrid multipoint-centralized video
6.8.5 Establishment of common mode
6.8.6 Multipoint rate matching
6.8.7 Multipoint lip synchronization
6.8.8
Multipoint encryption
6.8.9 Cascading multipoint control units
7
Call signalling
7.1 Addresses
7.1.1 Network address
7.1.2 TSAP identifier
7.1.3 Alias address
7.2 Registration, Admission and Status (RAS) channel
7.2.1 Gatekeeper discovery
7.2.2 Endpoint registration
7.2.3 Endpoint location
7.2.4
Admissions, bandwidth change, status and disengage
7.2.5 Access tokens
7.3 Call signalling channel
7.3.1 Call signalling channel routing
7.3.2 Control channel routing
7.3.3 Call Signalling and control protocol
revisions
7.4 Call reference value
7.5 Call ID
7.6 Conference ID and Conference Goal
8
Call signalling procedures
8.1 Phase A – Call setup
8.1.1 Basic call setup – Neither endpoint
registered
8.1.2 Both endpoints registered to the same
Gatekeeper
8.1.3 Only calling endpoint has Gatekeeper
8.1.4 Only called endpoint has Gatekeeper
8.1.5 Both endpoints registered to different
Gatekeepers
8.1.6 Optional Called Endpoint Signalling
8.1.7 Fast Connect Procedure
8.1.8 Call setup via gateways
8.1.9 Call setup with an MCU
8.1.10 Call forwarding
8.1.11 Broadcast call setup
8.1.12 Overlapped Sending
8.1.13 Call setup to conference alias
8.2 Phase B – Initial communication and capability exchange
8.2.1 Encapsulation of H.245 messages within
Q.931 messages
8.2.2 Tunnelling through intermediate
signalling entities
8.2.3 Switching to
a separate H.245 connection
8.3 Phase C – Establishment of audiovisual communication
8.3.1 Mode changes
8.3.2 Exchange of video by mutual agreement
8.3.3 Media stream address distribution
8.3.4 Correlation of media streams in
multipoint conferences
8.3.5 Communication Mode Command Procedures
8.4 Phase D – Call services
8.4.1 Bandwidth changes
8.4.2 Status
8.4.3 Ad hoc conference expansion
8.4.4 Supplementary services
8.4.5 Multipoint cascading
8.4.6 Third party initiated pause and
re-routing
8.5 Phase E – Call termination
8.5.1 Call clearing without a Gatekeeper
8.5.2 Call clearing with a Gatekeeper
8.5.3 Call clearing by Gatekeeper
8.6 Protocol failure handling
9
Interoperation with other terminal types
9.1 Speech-only terminals
9.2 Visual telephone terminals over the ISDN (H.320)
9.3 Visual telephone terminals over GSTN (H.324)
9.4 Visual telephone terminals over mobile radio (H.324/M)
9.5 Visual telephone terminals over ATM (H.321 and H.310 RAST)
9.6 Visual telephone terminals over guaranteed quality of service
LANs (H.322)
9.7 Simultaneous voice and data terminals over GSTN (V.70)
9.8 T.120 terminals on the packet based network
9.9 Gateway for H.323 Media Transport Over ATM
10 Optional enhancements
10.1 Encryption
10.2 Multipoint operation
10.2.1
H.243 Control and Indication
11 Maintenance
11.1 Loopbacks for maintenance purposes
11.2 Monitoring methods
Annex A – H.245 messages used by
H.323 endpoints
Annex B – Procedures for layered video codecs
B.1 Scope
B.2 Introduction
B.3 Scalability methods
B.4 Call establishment
B.5 Use of RTP sessions and codec layers
B.5.1 Associate base to audio for lip
synchronization
B.5.2
Enhancement layer dependency
B.6 Possible layering models
B.6.1 Multiple logical channels and RTP
sessions for a layered stream
B.6.2 Impact of one layer per logical channel
and per RTP session
B.7 Impact on multipoint conferences
B.7.1 MC Impartial model
B.7.2 MC Decision model
B.7.3 Multipoint conference containing
endpoints on different bandwidths
B.8 Use of network
QOS for layered video streams
Annex C – H.323 on ATM
C.1 Introduction
C.2 Scope
C.2.1 Point-to-point conferencing
C.2.2 MCU-based multipoint
C.2.3 H.323 interoperability with endpoints
using IP
C.3 Architecture
C.3.1 Overview of system
C.3.2 Interoperation with other ITU-T H-Series
endpoints
C.3.3 H.225.0 on IP over ATM
C.3.4 H.245 on TCP/IP over ATM
C.3.5 Addressing for A/V streams
C.3.6 Transport Capabilities added to
TransportCapability Set
C.3.7 Elements of ATM signalling
C.3.8 A/V
streams on RTP on AAL 5
C.3.9 QOS considerations (Optional)
C.4 Protocol section
C.4.1 ATM signalling information elements
C.4.2 H.245 Usage
C.4.3 RTP usage
C.4.4 Interoperation with H.323 on IP
Annex D – Real-time facsimile over H.323 systems
D.1 Introduction
D.2 Scope D.3 Normative references
D.4 Procedures for opening channels to
send T.38 packets
D.4.1 Opening the voice channel
D.4.2 Opening the facsimile channels
D.4.3 DTMF transmission
D.5 Non-Fast Start procedures
D.6 Usage of the MaxBitRate in
messages
D.7 Interactions with gateways and
T.38/Annex B devices
Appendix I – Sample MC to Terminal
Communication Mode Command
I.1 Sample conference Scenario A
I.2 CommunicationModeTable sent to all Endpoints
I.3 Sample conference Scenario B
I.4 CommunicationModeTable sent to all Endpoints
Appendix II – Transport Level
Resource Reservation Procedures
II.1 Introduction
II.2 QOS Support for H.323
II.3 RSVP background
II.4 The H.245 capability exchange phase
II.5 Open logical channel and setting up reservations
II.6 Close logical channel and tearing down reservations
II.7 Resource reservation for multicast H.323 logical channels
Appendix III – Gatekeeper Based
User Location
III.1 Introduction
III.2 Signalling
Appendix IV – Signalling
Prioritized Alternative Logical Channels in H.245
IV.1 Introduction
IV.2 Signalling