INTERNATIONAL TELECOMMUNICATION UNION
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`
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`TELECOMMUNICATION
`STANDARDIZATION SECTOR
`OF ITU
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`H.225.0
`
`(09/99)
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`SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS
`Infrastructure of audiovisual services – Transmission
`multiplexing and synchronization
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`
`Call signalling protocols and media stream
`packetization for packet-based multimedia
`communication systems
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`ITU-T Recommendation H.225.0
`(Previously CCITT Recommendation)
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`CISCO SYSTEMS, INC. Ex. 1019 Page 1
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`ITU-T H-SERIES RECOMMENDATIONS
`AUDIOVISUAL AND MULTIMEDIA SYSTEMS
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`
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`Characteristics of transmission channels used for other than telephone purposes
`Use of telephone-type circuits for voice-frequency telegraphy
`Telephone circuits or cables used for various types of telegraph transmission or
`simultaneous transmission
`Telephone-type circuits used for facsimile telegraphy
`Characteristics of data signals
`CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS
`INFRASTRUCTURE OF AUDIOVISUAL SERVICES
`General
`Transmission multiplexing and synchronization
`Systems aspects
`Communication procedures
`Coding of moving video
`Related systems aspects
`Systems and terminal equipment for audiovisual services
`Supplementary services for multimedia
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`
`
`For further details, please refer to ITU-T List of Recommendations.
`
`
`H.10–H.19
`H.20–H.29
`H.30–H.39
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`H.40–H.49
`H.50–H.99
`H.100–H.199
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`H.200–H.219
`H.220–H.229
`H.230–H.239
`H.240–H.259
`H.260–H.279
`H.280–H.299
`H.300–H.399
`H.450–H.499
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`ITU-T RECOMMENDATION H.225.0
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`
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`CALL SIGNALLING PROTOCOLS AND MEDIA STREAM PACKETIZATION
`FOR PACKET-BASED MULTIMEDIA COMMUNICATION SYSTEMS
`
`
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`
`
`Summary
`This Recommendation covers the technical requirements for narrow-band visual telephone services
`defined in H.200/AV.120-series Recommendations. In situations where the transmission path
`includes one or more packet-based networks, each of which is configured and managed to provide a
`non-guaranteed Quality of Service (QOS) which is not equivalent to that of N-ISDN, additional
`protection or recovery mechanisms, beyond those mandated by Recommendation H.320, need to be
`provided in the terminals. It is noted that Recommendation H.322 addresses the use of some other
`LANs which are able to provide the underlying performance not assumed by the H.323/H.225.0
`Recommendations.
`This Recommendation describes how audio, video, data, and control information on a packet-based
`network can be managed to provide conversational services in H.323 equipment.
`
`
`
`
`
`Source
`ITU-T Recommendation H.225.0 was revised by ITU-T Study Group 16 (1997-2000) and was
`approved under the WTSC Resolution No. 1 procedure on 30 September 1999.
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`Recommendation H.225.0 (09/99)
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`FOREWORD
`ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of
`telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of
`the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing
`Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
`The World Telecommunication Standardization Conference (WTSC), which meets every four years,
`establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on
`these topics.
`The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in
`WTSC Resolution No. 1.
`In some areas of information technology which fall within ITU-T’s purview, the necessary standards are
`prepared on a collaborative basis with ISO and IEC.
`
`
`
`
`NOTE
`In this Recommendation, the expression "Administration" is used for conciseness to indicate both a
`telecommunication administration and a recognized operating agency.
`
`
`
`INTELLECTUAL PROPERTY RIGHTS
`The ITU draws attention to the possibility that the practice or implementation of this Recommendation may
`involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence,
`validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others
`outside of the Recommendation development process.
`As of the date of approval of this Recommendation, the ITU had received notice of intellectual property,
`protected by patents, which may be required to implement this Recommendation. However, implementors are
`cautioned that this may not represent the latest information and are therefore strongly urged to consult the
`TSB patent database.
`
`
`
` ITU 2000
`All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means,
`electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU.
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`ii
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`Recommendation H.225.0 (09/99)
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`1
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`4
`4.1
`4.2
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`5
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`6
`6.1
`6.2
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`7
`7.1
`7.2
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`7.3
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`7.4
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`
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`CONTENTS
`
`Scope...........................................................................................................................
`
`References...................................................................................................................
`
`Definitions ..................................................................................................................
`
`Abbreviations..............................................................................................................
`General abbreviations .................................................................................................
`RAS message abbreviations........................................................................................
`
`Conventions ................................................................................................................
`
`Packetization and synchronization mechanism ..........................................................
`General approach ........................................................................................................
`Use of RTP/RTCP ......................................................................................................
`6.2.1 Audio .............................................................................................................
`6.2.2 Video messages .............................................................................................
`6.2.3 Data messages................................................................................................
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`H.225.0 message definitions.......................................................................................
`Use of Q.931 messages...............................................................................................
`Common Q.931 Information Elements.......................................................................
`7.2.1 Header Information Elements........................................................................
`7.2.2 Message-specific information elements ........................................................
`Q.931 message details.................................................................................................
`7.3.1 Alerting..........................................................................................................
`7.3.2 Call Proceeding..............................................................................................
`7.3.3 Connect..........................................................................................................
`7.3.4 Connect Acknowledge...................................................................................
`7.3.5 Disconnect .....................................................................................................
`7.3.6
`Information ....................................................................................................
`7.3.7 Progress .........................................................................................................
`7.3.8 Release...........................................................................................................
`7.3.9 Release Complete ..........................................................................................
`7.3.10 Setup ..............................................................................................................
`7.3.11 Setup Acknowledge.......................................................................................
`7.3.12 Status .............................................................................................................
`7.3.13 Status Inquiry.................................................................................................
`Q.932 message details.................................................................................................
`7.4.1 Facility...........................................................................................................
`7.4.2 Notify.............................................................................................................
`7.4.3 Other messages ..............................................................................................
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`7.5
`7.6
`7.7
`7.8
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`7.9
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`7.10
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`7.11
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`Q.931 timer values......................................................................................................
`H.225.0 common message elements...........................................................................
`Required Support of RAS messages...........................................................................
`Terminal and Gateway Discovery messages...............................................................
`7.8.1 GatekeeperRequest (GRQ) ............................................................................
`7.8.2 GatekeeperConfirm (GCF) ............................................................................
`7.8.3 GatekeeperReject (GRJ) ................................................................................
`Terminal and Gateway Registration messages ...........................................................
`7.9.1 RegistrationRequest (RRQ)...........................................................................
`7.9.2 RegistrationConfirm (RCF)...........................................................................
`7.9.3 RegistrationReject (RRJ)...............................................................................
`Terminal/Gatekeeper Unregistration messages ..........................................................
`7.10.1 UnregistrationRequest (URQ) .......................................................................
`7.10.2 UnregistrationConfirm (UCF) .......................................................................
`7.10.3 UnregistrationReject (URJ) ...........................................................................
`Terminal to Gatekeeper Admission messages ............................................................
`7.11.1 AdmissionRequest (ARQ).............................................................................
`7.11.2 AdmissionConfirm (ACF).............................................................................
`7.11.3 AdmissionReject (ARJ).................................................................................
`Terminal to gatekeeper requests for changes in bandwidth........................................
`7.12.1 BandwidthRequest (BRQ).............................................................................
`7.12.2 BandwidthConfirm (BCF).............................................................................
`7.12.3 BandwidthReject (BRJ).................................................................................
`Location Request messages ........................................................................................
`7.13.1 LocationRequest (LRQ).................................................................................
`7.13.2 LocationConfirm (LCF).................................................................................
`7.13.3 LocationReject (LRJ).....................................................................................
`7.14 Disengage messages....................................................................................................
`7.14.1 DisengageRequest (DRQ) .............................................................................
`7.14.2 DisengageConfirm (DCF) .............................................................................
`7.14.3 DisengageReject (DRJ) .................................................................................
`Status Request messages.............................................................................................
`7.15.1 InfoRequest (IRQ) .........................................................................................
`7.15.2 InfoRequestResponse (IRR) ..........................................................................
`7.15.3 InfoRequestAck (IACK)................................................................................
`7.15.4 InfoRequestNak (INAK)................................................................................
`7.16 Non-Standard message................................................................................................
`7.17 Message Not Understood............................................................................................
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`7.15
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`7.12
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`7.13
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`7.18 Gateway Resource Availability messages...................................................................
`7.18.1 ResourcesAvailableIndicate (RAI) ................................................................
`7.18.2 ResourcesAvailableConfirm (RAC)..............................................................
`7.19 RAS timers and Request in Progress (RIP) ................................................................
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`8
`8.1
`8.2
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`8.3
`8.4
`8.5
`8.6
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`Mechanisms for maintaining QOS..............................................................................
`General approach and assumptions.............................................................................
`Use of RTCP in measuring QOS ................................................................................
`8.2.1 Sender reports................................................................................................
`8.2.2 Receiver Reports............................................................................................
`Audio/Video jitter procedures.....................................................................................
`Audio/Video Skew Procedures...................................................................................
`Procedures for maintaining QOS................................................................................
`Echo Control...............................................................................................................
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`A.3
`A.4
`A.5
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`A.6
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`Annex A – RTP/RTCP.............................................................................................................
`A.1
`Introduction.................................................................................................................
`A.2
`RTP use scenarios.......................................................................................................
`A.2.1 Simple multicast audio conference................................................................
`A.2.2 Audio and video conference ..........................................................................
`A.2.3 Mixers and translators ...................................................................................
`Definitions ..................................................................................................................
`Byte order, alignment and time format .......................................................................
`RTP data transfer protocol..........................................................................................
`A.5.1 RTP fixed header fields .................................................................................
`A.5.2 Multiplexing RTP sessions............................................................................
`A.5.3 Profile-specific modifications to the RTP header..........................................
`RTP Control Protocol (RTCP)....................................................................................
`A.6.1 RTCP packet format ......................................................................................
`A.6.2 RTCP transmission interval...........................................................................
`A.6.3 Sender and receiver reports ...........................................................................
`A.6.4 SDES: Source Description RTCP packet ......................................................
`A.6.5 BYE: Goodbye RTCP packet ........................................................................
`A.6.6 APP: Application-defined RTCP packet .......................................................
`RTP translators and mixers.........................................................................................
`A.7.1 General description........................................................................................
`A.7.2 RTCP processing in translators .....................................................................
`A.7.3 RTCP Processing in mixers...........................................................................
`A.7.4 Cascaded mixers............................................................................................
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`A.7
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`A.8
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`SSRC identifier allocation and use .............................................................................
`A.8.1 Probability of Collision .................................................................................
`A.8.2 Collision resolution and loop detection.........................................................
`Security .......................................................................................................................
`A.9
`A.10 RTP over network and transport protocols .................................................................
`A.11 Summary of protocol constants ..................................................................................
`A.11.1 RTCP packet types ........................................................................................
`A.11.2 SDES types ....................................................................................................
`A.12 RTP profiles and payload format specifications.........................................................
`A.13 Algorithms ..................................................................................................................
`A.14 Bibliography................................................................................................................
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`Annex B – RTP Profile ............................................................................................................
`B.1
`Introduction.................................................................................................................
`B.2
`RTP and RTCP packet forms and protocol behaviour................................................
`B.3
`Payload types ..............................................................................................................
`B.4
`Audio ..........................................................................................................................
`B.4.1 Encoding-independent recommendations......................................................
`B.4.2 Guidelines for sample-based audio encodings ..............................................
`B.4.3 Guidelines for frame-based audio encodings.................................................
`B.4.4 Audio encodings............................................................................................
`Video...........................................................................................................................
`Payload type definitions..............................................................................................
`Port assignment...........................................................................................................
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`B.5
`B.6
`B.7
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`C.3
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`Annex C – RTP payload format for H.261 video streams .......................................................
`C.1
`Introduction.................................................................................................................
`C.2
`Structure of the packet stream.....................................................................................
`C.2.1 Overview of Recommendation H.261 ...........................................................
`C.2.2 Considerations for packetization ...................................................................
`Specification of the packetization scheme..................................................................
`C.3.1 Usage of RTP.................................................................................................
`C.3.2 Recommendations for operation with hardware codecs................................
`C.3.3 Packet loss issues...........................................................................................
`C.3.4 Use of optional H.261-specific control packets.............................................
`C.3.5 Control packets definition .............................................................................
`Bibliography................................................................................................................
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`C.4
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`Annex D – RTP payload format for H.261A video streams ....................................................
`D.1
`Introduction.................................................................................................................
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`D.2
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`H.261A RTP packetization.........................................................................................
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`Annex E – Video packetization ...............................................................................................
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`Annex F – Audio packetization ...............................................................................................
`F.1
`G.723.1........................................................................................................................
`F.2
`G.728...........................................................................................................................
`F.3
`G.729...........................................................................................................................
`F.4
`Silence suppression.....................................................................................................
`F.5
`GSM Codecs...............................................................................................................
`F.5.1 Frame Packetization ......................................................................................
`F.5.2
`Informative References..................................................................................
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`Annex G – Communication between administrative domains.................................................
`G.1
`Scope...........................................................................................................................
`G.2
`Definitions ..................................................................................................................
`G.3
`Abbreviations..............................................................................................................
`G.4
`References...................................................................................................................
`G.5
`System Models............................................................................................................
`G.5.1 Hierarchical....................................................................................................
`G.5.2 Distributed or Full Mesh................................................................................
`G.5.3 Clearing House ..............................................................................................
`G.5.4 Aggregation Point..........................................................................................
`G.5.5 Overlapping Administrative Domains...........................................................
`Addressing Conventions.............................................................................................
`Operation ....................................................................................................................
`G.7.1 Address Templates and Descriptors ..............................................................
`G.7.2 Discovery of a Border Element or Set of Border Elements...........................
`G.7.3 Resolution Procedures ...................................................................................
`G.7.4 Usage Information Exchange.........................................................................
`Protocol.......................................................................................................................
`G.8.1 Security Considerations.................................................................................
`G.8.2 Message Definitions ......................................................................................
`Signalling Examples ...................................................................................................
`G.9.1 Distributed or Full Mesh................................................................................
`G.9.2 Clearing House ..............................................................................................
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`G.8
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`G.9
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`G.6
`G.7
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`Annex H – H.225.0 Message Syntax (ASN.1).........................................................................
`Annex I – H.263+ Video Packetization ...................................................................................
`Appendix I – RTP/RTCP algorithms.......................................................................................
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`Appendix II – RTP profile .......................................................................................................
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`Appendix III – H.261 packetization.........................................................................................
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`Appendix IV – H.225.0 operation on different packet-based network protocol stacks ...........
`IV.1
`TCP/IP/UDP ...............................................................................................................
`IV.1.1 Discovering the gatekeeper............................................................................
`IV.1.2 Endpoint-to-endpoint communications .........................................................
`SPX/IPX......................................................................................................................
`IV.2.1 Discovering the gatekeeper............................................................................
`IV.2.2 Endpoint-to-endpoint communication...........................................................
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`IV.2
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`Recommendation H.225.0
`
`CALL SIGNALLING PROTOCOLS AND MEDIA STREAM PACKETIZATION
`FOR PACKET-BASED MULTIMEDIA COMMUNICATION SYSTEMS
`(revised in 1999)
`
`The ITU-T,
`considering
`the widespread adoption of and the increasing use of Recommendation H.320 for videophony and
`videoconferencing services over networks conforming to the N-ISDN characteristics specified in the
`I-series Recommendations,
`appreciating
`the desirability and benefits of enabling the above services to be carried, wholly or in part, over
`Local Area Networks while also maintaining the capability of interworking with H.320 terminals,
`and noting
`the characteristics and performances of the many types of Local Area Network which are of potential
`interest,
`recommends
`that systems and equipment meeting the requirements of Recommendations H.322 or H.323 are
`utilized to provide these facilities.
`
`Scope
`1
`This Recommendation describes the means by which audio, video, data, and control are associated,
`coded, and packetized for transport between H.323 equipment on a packet-based network. This
`includes the use of an H.323 gateway, which in turn may be connected to H.320, H.324, or
`H.310/H.321 terminals on N-ISDN, GSTN, or B-ISDN respectively. The equipment descriptions and
`procedures are described in Recommendation H.323 while this Recommendation covers protocols
`and message formats. Communication via an H.323 gateway to an H.322 gateway for guaranteed
`Quality of Service (QOS) LANs and thus to H.322 endpoints is also possible.
`This Recommendation is intended to operate over a variety of different packet-based networks,
`including IEEE 802.3, Token Ring, etc. Thus, this Recommendation is defined as being above the
`Transport layer such as TCP/IP/UDP, SPX/IPX, etc. Specific profiles for particular transport
`protocol suites are included in Appendix IV. Thus, the scope of H.225.0 communication is between
`H.323 entities on the same packet-based network, using the same transport protocol. This
`packet-based network may be a single segment or ring, or it logically could be an enterprise data
`network comprising multiple packet-based networks bridged or routed to create one interconnected
`network. It should be emphasized that operation of H.323 terminals over the entire Internet, or even
`several connected packet-based networks may result in poor performance. The possible means by
`which quality of service might be assured on this packet-based network, or on the Internet in general
`is beyond the scope of this Recommendation. However, this Recommendation provides a means for
`the user of H.323 equipment to determine that quality problems are the result of packet-based
`network congestion, as well as procedures for corrective actions. It is also noted that the use of
`multiple H.323 gateways connected over the public ISDN network is a straightforward method for
`increasing quality of service.
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`Recommendation H.323 and this Recommendation are intended to extend Recommendations H.320
`and H.221 connections onto the non-guaranteed QOS packet-based network environment
`conferences. As such the primary conference model1 is one with size in the range of a few
`participants to a few thousand, as opposed to large-scale broadcast operations, with strong admission
`control, and tight conference control.
`This Recommendation makes use of (RTP/RTCP) Real-time Transport Protocol/Real-Time
`Transport Control Protocol for media stream packetization and synchronization for all underlying
`packet-based networks (see Annexes A, B and C). Please note that the usage of RTP/RTCP as