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
6.3.1 Gateway decomposition
6.3.2 Gateway applications
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
6.9 Models for supplementary services
7 Call signalling
7.1 Addresses
7.1.1 Network address
7.1.2 TSAP identifier
7.1.3 Alias address
7.1.4 H.323 URL scheme
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
7.2.6 Alternate gatekeeper procedures
7.2.7 Usage information reporting
7.2.8 Call credit-related capabilities
7.2.9 Alternate transport addresses
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
7.7 Endpoint call capacity
7.8 Caller identification services
7.8.1 Description of services
7.8.2 Messages and information elements
7.8.3 Actions at the originating endpoint
7.8.4 Actions at the terminating endpoint
7.8.5 Actions at a gatekeeper
7.9 Generic extensible framework
7.9.1 Format of a GenericData structure
7.9.2 Negotiation using the extensible framework‑general
7.9.3 Negotiation using the extensible
framework-RAS
7.9.4 Negotiation using the extensible framework – call signalling
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
8.1.14 Gatekeeper modification of destination addresses
8.1.15 Indicating desired protocols
8.1.16 Gatekeeper requested tones and announcements
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
8.2.4 Initiating H.245 tunnelling in parallel with fast connect
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 (ITU-T Rec. H.320)
9.3 Visual telephone terminals over
GSTN (ITU-T Rec. H.324)
9.4 Visual telephone terminals over
mobile radio (ITU-T Rec. H.324/M - Annex C/H.324)
9.5 Visual telephone terminals over
ATM (H.321 and H.310 RAST)
9.6 Visual telephone terminals over
guaranteed quality of service LANs (ITU‑T Rec. H.322)
9.7 Simultaneous voice and data
terminals over GSTN (ITU-T Rec. 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
10.3 Call Linkage in H.323
10.3.1 Description
10.3.2 Invocation and operation
10.3.3 Interaction with H.450 supplementary services
10.4 Tunnelling of non-H.323 signalling
messages
10.4.1 Indicating support of tunnelled
protocols
10.4.2 Requesting a specific protocol tunnel to a gatekeeper
10.4.3 Tunnelling a signalling protocol in H.225.0 call signalling messages
10.4.4 Gatekeeper considerations
10.5 Use of RTP payload for DTMF
digits, telephony tones and telephony signals
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 Recommendations 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 AAL5
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 Procedures for opening channels to
send T.38 packets
D.3.1 Opening the voice channel
D.3.2 Opening the facsimile channels
D.3.3 DTMF transmission
D.4 Non-Fast Connect procedures
D.5 Replacing an existing audio stream
with a T.38 fax stream
D.6 Usage of the MaxBitRate in
messages
D.7 Interactions with gateways and
T.38/Annex B devices
Annex E -
Framework and wire‑protocol for multiplexed call signalling
transport
E.1 Scope
E.1.1 Introduction
E.1.2 Signalling models
E.1.3 Optional payload fields
E.1.4 Wire-protocol
E.2 H.225.0 call signalling over Annex
E
E.2.1 Rationale
E.2.2 H.323 Call-Setup using this annex
E.2.3 Specifics
Annex F -Simple endpoint
types
F.1 Introduction
F.2 Specification conventions
F.3 Scope
F.4 Normative references
F.5 Abbreviations
F.6 Simple (Audio) Endpoint Type – System functionality overview
F.7 Procedures for Simple Endpoint
Types
F.7.1 RAS Signalling (H.225.0 RAS)
F.7.2 Call signalling (H.225.0 Call Control)
F.7.3 Multimedia system control signalling (H.245)
F.7.4 Media Exchange
F.7.5 Supplementary services (H.450.x)
F.7.6 Third-party initiated pause and re-routing
F.7.7 Conference-mode Operation
F.7.8 Support for loosely-coupled conferences (ITU‑T Rec. H.332)
F.7.9 Management Information Bases (MIBs)
F.8 Security extensions
F.9 Interoperability considerations
F.10 Implementation notes (Informative)
F.10.1 Open Logical Channel
Annex G - Text conversation
and Text SET
G.1 Introduction
G.2 Scope
G.3 References
G.4 Definitions
G.5 Procedures for opening channels for T.140
text conversation
G.6 Framing and buffering of T.140
data
G.6.1 Common considerations
G.6.2 Usage of reliable channels
G.6.3 Usage of unreliable channels
G.7 Interaction with text conversation
facilities in other devices
G.8 Multipoint considerations
G.8.1 Situations for multipoint text conversation
G.9 Text SET: Text Conversation Simple
Endpoint Type
G.9.1 Introduction to Text SET
G.9.2 Text SET System Functionality Overview (F.6/H.323)
G.9.3 Procedures for Text SET devices (F.7/H.323)
G.9.4 RAS Signalling (H.225.0 RAS - F.7.1/H.323)
G.9.5 Call Signalling (H.225.0 Call Control - F.7.2/H.323)
G.9.6 Data Capability (F.7.3.3.3/H.323)
G.9.7 Additional rules for usage of capabilities (F.7.3.3.9/H.323)
G.9.8 Logical Channel Signalling Messages (F.7.3.4/H.323)
G.9.9 Media Exchange (F.7.4/H.323)
G.9.10 Initiating side (F.7.6.1/H.323)
G.9.11 Conference-unaware Text SET
terminals (F.7.7.1/H.323)
G.9.12 Support for loosely-coupled conferences (ITU‑T Rec. H.332)
(F.7.8/H.323)
Annex J - Security for H.323 Annex F
J.1 Introduction
J.2 Specification conventions
J.3 Scope
J.4 Abbreviations
J.5 Normative references
J.6 Secure Audio Simple Endpoint Type
(SASET)
J.6.1 Assumptions
J.6.2 Overview
Annex K - HTTP‑based
service control transport channel
K.1 Introduction
K.1.1 Notation
K.2 Service control in H.323
K.2.1 Service control session
K.2.2 Non‑call‑related
service control
K.2.3 Call-related service control
K.3 Usage of HTTP
K.3.1 Non-call-related services control channel
K.3.2 Call-related services control channel
K.4 Example scenarios
K.5 References
K.5.1 Normative references
K.5.2 Informative references
Annex L -
Stimulus control protocol
L.1 Scope
L.1.1 Terminology
L.1.2 Relationship of H.323 stimulus to H.248
L.1.3 Relationship of H.323 stimulus to HTTP
L.1.4 Relationship to H.450 supplementary services
L.2 Introduction
L.3 Stimulus framework
L.3.1 Overview
L.3.2 Protocol signalling
L.3.3 Use of H.248
L.3.4 H.225.0 encapsulation
L.4 References
Annex M1 - Tunnelling of
signalling protocols (QSig) in H.323
M1.1 Scope
M1.2 Normative references
M1.3 Endpoint procedures
M1.4 Tunnelling of QSIG connection
oriented call independent signalling
M1.5 Gatekeeper procedures
Annex M2 - Tunnelling of
signaling protocols (ISUP) in H.323
M2.1 Scope
M2.2 Normative references
M2.3 Endpoint procedures
M2.4 Gatekeeper procedures
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
II.8 Synchronized RSVP
II.8.1 Synchronizing RSVP when not using Fast Connect
II.8.2 Synchronizing RSVP with fast connect
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
Appendix V - Use
of E.164 and ISO/IEC 11571 numbering plans
V.1 E.164 numbering plan
V.2 Private network number
V.3 H.323 versions 1, 2 and 3 usage