1、 International Telecommunication Union ITU-T J.163TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2007) SERIES J: CABLE NETWORKS AND TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS IPCablecom Dynamic quality of service for the provision of real-time services over cable t
2、elevision networks using cable modems ITU-T Recommendation J.163 ITU-T Rec. J.163 (12/2007) i ITU-T Recommendation J.163 Dynamic quality of service for the provision of real-time services over cable television networks using cable modems Summary ITU-T Recommendation J.163 addresses requirements for
3、a client device to obtain access to network resources. In particular, it specifies a comprehensive mechanism for a client device to request a specific quality of service from the DOCSIS network. Extensive examples illustrate the use of this Recommendation. The scope of this Recommendation is to defi
4、ne the QoS architecture for the “Access“ portion of the IPCablecom network, provided to requesting applications on a per-flow basis. The access portion of the network is defined to be between the multimedia terminal adapter (MTA) and the cable modem termination system (CMTS), including the DOCSIS ne
5、twork. The method of QoS allocation over the backbone is unspecified in this Recommendation. Interface to the managed IP backbone and issues related to IP multicast are not within the scope of this Recommendation. This Recommendation also recognizes that per-flow reservations may be required within
6、the customer premises, and the protocol developed addresses this potential need. Source ITU-T Recommendation J.163 was approved on 14 December 2007 by ITU-T Study Group 9 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. J.163 (12/2007) FOREWORD The International Telecommunicat
7、ion Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff ques
8、tions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendation
9、s on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation,
10、the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or ap
11、plicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance wit
12、h the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or appli
13、cability 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, ITU had not received notice of intellectual property, protected by patents, which may be required to imple
14、ment this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2008 All rights reserved. No part of this publication may be reproduced, by any me
15、ans whatsoever, without the prior written permission of ITU. ITU-T Rec. J.163 (12/2007) iii CONTENTS Page 1 Scope 1 2 References. 1 2.1 Normative references 1 2.2 Informative references 2 3 Terms and definitions . 2 4 Abbreviations and conventions. 2 4.1 Abbreviations . 2 4.2 Conventions 3 5 Technic
16、al overview. 3 5.1 IPCablecom QoS architecture requirements 5 5.2 IP QoS access network elements 7 5.3 IPCablecom dynamic QoS architecture 8 5.4 QoS interfaces 9 5.5 Framework for IPCablecom QoS . 10 5.6 Requirements of access network resource management 12 5.7 Theory of operation 17 6 Embedded MTA
17、to CM QoS Protocol (pkt-q1) . 22 6.1 RSVP flowspecs . 23 6.2 DOCSIS support for resource reservation 34 6.3 Use of DOCSIS MAC control service interface. 40 7 Authorization interface description (pkt-q6) 44 7.1 Gates: The framework for QoS control 45 7.2 COPS profile for IPCablecom 50 7.3 Gate contro
18、l protocol message formats 52 7.4 Gate control protocol operation 62 7.5 CMS use of gate protocol. 68 7.6 Gate-coordination. 68 Annex A Timer definitions and values 71 Appendix I Theft of service scenarios 73 I.1 Scenario No. 1: Customers establishing high QoS connections themselves 73 I.2 Scenario
19、No. 2: Customers using provisioned QoS for non-voice applications. 74 I.3 Scenario No. 3: MTA altering the destination address in voice packets 74 I.4 Scenario No. 4: Use of half-connections 74 I.5 Scenario No. 6: Early termination leaving a half-connection 74 I.6 Scenario No. 6: Forged gate coordin
20、ation messages 74 I.7 Scenario No. 7: Fraud directed against unwanted callers. 75 iv ITU-T Rec. J.163 (12/2007) Page Appendix II COPS (common open policy service) 76 II.1 COPS procedures and principles 76 II.2 Comparison of COPS and LDAP for policy 77 Appendix III TCP considerations . 78 III.1 Requi
21、rements 78 III.2 Recommended changes 78 III.3 TCP connection establishment impacting post-dial delay 79 III.4 Need for low latency for packets between the GC and CMTS, even under loss 79 III.5 Head-of-line blocking. 80 III.6 TCP slow start 80 III.7 Delaying of packets: Nagles algorithm 81 III.8 Non-
22、blocking interface. 81 ITU-T Rec. J.163 (12/2007) 1 ITU-T Recommendation J.163 Dynamic quality of service for the provision of real-time services over cable television networks using cable modems 1 Scope This Recommendation addresses requirements for a client device to obtain access to network resou
23、rces. In particular, it specifies a comprehensive mechanism for a client device to request a specific quality of service from the DOCSIS network. Extensive examples illustrate the use of this Recommendation. The scope of this Recommendation is to define the QoS architecture for the “Access“ portion
24、of the IPCablecom network, provided to requesting applications on a per-flow basis. The access portion of the network is defined to be between the multimedia terminal adapter (MTA) and the cable modem termination system (CMTS), including the DOCSIS network. The method of QoS allocation over the back
25、bone is unspecified in this Recommendation. Interface to the managed IP backbone and issues related to IP multicast are not within the scope of this Recommendation. This Recommendation also recognizes that per-flow reservations may be required within the customer premises, and the protocol developed
26、 addresses this potential need. NOTE The structure and content of this Recommendation have been organized for ease of use by those familiar with the original source material; as such, the usual style of ITU-T recommendations has not been applied. 2 References 2.1 Normative references The following I
27、TU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendat
28、ion are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give i
29、t, as a stand-alone document, the status of a Recommendation. ITU-T J.83 ITU-T Recommendation J.83 (2007), Digital multi-programme systems for television, sound and data services for cable distribution. ITU-T J.112 ITU-T Recommendation J.112 (1998), Transmission systems for interactive cable televis
30、ion services. ITU-T J.112-A ITU-T Recommendation J.112 Annex A (2001), Digital Video Broadcasting: DVB interaction channel for Cable TV (CATV) distribution systems. ITU-T J.112-B ITU-T Recommendation J.112 Annex B (2004), Data-over-cable service interface specifications: Radio-frequency interface sp
31、ecification. ITU-T J.160 ITU-T Recommendation J.160 (2005), Architectural framework for the delivery of time-critical services over cable television networks using cable modems. ITU-T J.161 ITU-T Recommendation J.161 (2007), Audio and video codec requirements and usage for the provision of bidirecti
32、onal audio services over cable television networks using cable modems. IETF RFC 2748 IETF RFC 2748 (2000), The COPS (Common Open Policy Service) Protocol. 2 ITU-T Rec. J.163 (12/2007) 2.2 Informative references ITU-T G.114 ITU-T Recommendation G.114 (2003), One-way transmission time. ITU-T G.711 ITU
33、-T Recommendation G.711 (1988), Pulse code modulation (PCM) of voice frequencies. ITU-T G.726 ITU-T Recommendation G.726 (1990), 40, 32, 24, 16 kbit/s adaptive differential pulse code modulation (ADPCM). ITU-T G.728 ITU-T Recommendation G.728 (1992), Coding of speech at 16 kbit/s using low-delay cod
34、e excited linear prediction. ITU-T G.729 ITU-T Recommendation G.729 Annex E (1998), 11.8 kbit/s CS-ACELP speech coding algorithm. ITU-T J.162 ITU-T Recommendation J.162 (2007), Network call signalling protocol for the delivery of time-critical services over cable television networks using cable mode
35、ms. ITU-T J.164 ITU-T Recommendation J.164 (2007), Event message requirements for the support of real-time services over cable television networks using cable modems. ITU-T J.170 ITU-T Recommendation J.170 (2005), IPCablecom security specification. IETF RFC 791 IETF RFC 791 (1981), Internet Protocol
36、 DARPA Internet Program Protocol specification. IETF RFC 2327 IETF RFC 2327 (1998), SDP: Session Description Protocol. IETF RFC 2474 IETF RFC 2474 (1998), Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers. IETF RFC 2753 IETF RFC 2753 (2000), A Framework for Poli
37、cy-based Admission Control. IETF RFC 3551 IETF RFC 3551 (2003), RTP Profile for Audio and Video Conferences with Minimal control. 3 Terms and definitions This Recommendation defines the following terms: 3.1 cable modem: A cable modem is a layer two termination device that terminates the customer end
38、 of the J.112 (or J.122) connection. 3.2 DOCSIS flow: A unidirectional or bidirectional flow of data packets that is subject to MAC-layer signalling and QoS assignment compliant to ITU-T J.112 (or ITU-T Rec. J.122). 3.3 IPCablecom: An ITU-T project that includes an architecture and a series of Recom
39、mendations that enable the delivery of real-time services over the cable television networks using cable modems. 4 Abbreviations and conventions 4.1 Abbreviations This Recommendation uses the following abbreviations: CM Cable Modem CMTS Cable Modem Termination System COPS Common Open Policy Service
40、ITU-T Rec. J.163 (12/2007) 3 CPE Customer Premises Equipment DCS Distributed Call Signalling DSA Dynamic Service Addition DSC Dynamic Service Change INA Interactive Network Adapter IP Internet Protocol MTA Multimedia Terminal Adapter NCS Network-based Call Signalling PHS Payload Header Suppression P
41、STN Public Switched Telephone Network QoS Quality of Service RAP Resource Allocation Protocol RSVP Resource ReSerVation Protocol TLV Type-Length-Value VAD Voice Activity Detection 4.2 Conventions Throughout this Recommendation, the words that are used to define the significance of particular require
42、ments are capitalized. These words are: “MUST“ This word or the adjective “REQUIRED“ means that the item is an absolute requirement of this Recommendation. “MUST NOT“ This phrase means that the item is an absolute prohibition of this Recommendation. “SHOULD“ This word or the adjective “RECOMMENDED“
43、means that there may exist valid reasons in particular circumstances to ignore this item, but the full implications should be understood and the case carefully weighed before choosing a different course. “SHOULD NOT“ This phrase means that there may exist valid reasons in particular circumstances wh
44、en the listed behaviour is acceptable or even useful, but the full implications should be understood and the case carefully weighed before implementing any behaviour described with this label. “MAY“ This word or the adjective “OPTIONAL“ means that this item is truly optional. One vendor may choose t
45、o include the item because a particular marketplace requires it or because it enhances the product, for example; another vendor may omit the same item. 5 Technical overview Enhanced quality of service is required for supporting interactive multimedia applications. Resources may be constrained in seg
46、ments of the network, requiring allocation of resources in the network. The scope of this Recommendation is to define the Quality of Service architecture for the “Access“ portion of the IPCablecom network. The access portion of the network is defined to be between the multimedia terminal adapter (MT
47、A) and the cable modem termination system (CMTS), including the DOCSIS network. This Recommendation also recognizes that per-flow reservations 4 ITU-T Rec. J.163 (12/2007) may be required within the customer premises, and the protocols developed herein address this potential need. Although some segm
48、ents of the backbone network may require resource reservation to provide adequate quality of service, we consider the protocols for backbone resource management to be outside the scope of this Recommendation. Resources are allocated on the DOCSIS network for individual flows associated with each ses
49、sion of an application, per subscriber, on an authorized and authenticated basis. A DQoS session, or simply a session, is defined by this Recommendation to be a single bidirectional data flow between two clients. When a multimedia application needs multiple bidirectional data flows (e.g., one for voice and a separate for video), separate DQoS sessions are established for each. Applications may use only half of the sessions bidirectional data flow, thereby providing send-only or receive-only services. For example, in a typical voic
