1、 International Telecommunication Union ITU-T J.122TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2007) SERIES J: CABLE NETWORKS AND TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Interactive systems for digital television distribution Second-generation transmission sys
2、tems for interactive cable television services IP cable modems Recommendation ITU-T J.122 Rec. ITU-T J.122 (12/2007) i Recommendation ITU-T J.122 Second-generation transmission systems for interactive cable television services IP cable modems Summary This Recommendation describes transmission system
3、s that are consistent with those described in ITU-T Recommendation J.112. Its purpose is to provide a technology through which the demand for symmetrical services on cable networks can be met. This second-generation technology, while using the same RF channel, is backward compatible with that of ITU
4、-T Recommendation J.112. It provides a significant increase in upstream channel capacity with wider channels, higher symbol rate and increased spectral efficiency. It provides for both Synchronous-CDMA and Advanced-TDMA coding and also adds higher order modulation capabilities. It is more robust wit
5、h regard to noise immunity and provides greater multipath protection than the technology used in ITU-T Recommendation J.112. Source Recommendation ITU-T J.122 was approved on 14 December 2007 by ITU-T Study Group 9 (2005-2008) under Recommendation ITU-T A.8 procedure. ii Rec. ITU-T J.122 (12/2007) F
6、OREWORD The International Telecommunication 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 study
7、ing technical, operating and tariff questions 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 group
8、s which, in turn, produce Recommendations 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 IS
9、O and IEC. NOTE In this Recommendation, 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 provision
10、s (to ensure e.g. interoperability or applicability) 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 wo
11、rds does not suggest that compliance with 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 co
12、ncerning 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, ITU had not received notice of intellectual property, protected by
13、 patents, which may be required to implement 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 2009 All rights reserved. No part of this
14、publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T J.122 (12/2007) iii CONTENTS Page 1 Scope and purpose 1 1.1 Scope 1 1.2 Requirements 1 1.3 Background. 2 1.4 Conventions for this Recommendation 4 2 References. 4 2.1 Normative references
15、4 2.2 Informative references 6 3 Glossary 7 3.1 Abbreviations and acronyms 7 3.2 Terms and definitions. 9 4 Functional assumptions 17 4.1 Broadband access network . 17 4.2 Equipment assumptions 18 4.3 RF channel assumptions. 18 4.4 Transmission levels 20 4.5 Frequency inversion . 21 5 Communication
16、protocols. 21 5.1 Protocol stack . 21 5.2 The MAC forwarder. 25 5.3 Network layer . 27 5.4 Above the network layer 29 5.5 Data link layer 30 5.6 Physical layer 30 6 Physical media dependent sublayer specification. 31 6.1 Scope 31 6.2 Upstream. 31 6.3 Downstream 88 7 Downstream transmission convergen
17、ce sublayer. 94 7.1 Introduction 94 7.2 MPEG packet format 95 7.3 MPEG header for DOCS data-over-cable 95 7.4 MPEG payload for DOCS data-over-cable 96 7.5 Interaction with the MAC sublayer 96 7.6 Interaction with the Physical Layer 98 7.7 MPEG header synchronization and recovery. 98 8 Media access c
18、ontrol specification . 98 8.1 Introduction 98 iv Rec. ITU-T J.122 (12/2007) Page 8.2 MAC frame formats . 101 8.3 MAC management messages . 121 9 Media access control protocol operation 172 9.1 Upstream bandwidth allocation 172 9.2 Support for multiple channels 181 9.3 Timing and synchronization. 181
19、 9.4 Upstream transmission and contention resolution 185 9.5 Data link encryption support 187 10 Quality of service and fragmentation . 188 10.1 Theory of operation 188 10.2 Upstream service flow scheduling services 203 10.3 Fragmentation. 207 10.4 Payload header suppression 214 11 Cable modem CMTS
20、interaction. 221 11.1 CMTS initialization 221 11.2 Cable modem initialization. 221 11.3 Standard operation 243 11.4 Dynamic service . 250 11.5 Fault detection and recovery 309 12 Supporting future new cable modem capabilities. 310 12.1 Downloading cable modem operating software. 310 Annex A Well-kno
21、wn addresses. 312 A.1 MAC addresses. 312 A.2 MAC service IDs 312 A.3 MPEG PID 313 Annex B Parameters and constants. 314 Annex C Common radio frequency interface encodings 317 C.1 Encodings for configuration and MAC-layer messaging. 317 C.2 Quality-of-service-related encodings . 342 C.3 Encodings for
22、 other interfaces 366 C.4 Confirmation code 367 Annex D CM configuration interface specification 371 D.1 CM IP addressing . 371 D.2 CM configuration . 372 D.3 Configuration verification 376 Annex E The data-over-cable spanning tree protocol. 378 E.1 Background. 378 E.2 Public spanning tree . 378 E.3
23、 Public spanning tree protocol details 379 Rec. ITU-T J.122 (12/2007) v Page E.4 Spanning tree parameters and defaults. 380 Annex F European specification additions . 382 F.1 Scope and purpose 382 F.2 References 382 F.3 Glossary 382 F.4 Functional assumptions 382 F.5 Communication protocols 385 F.6
24、Physical media dependent sublayer specification 386 F.7 Downstream transmission convergence sublayer. 407 F.8 Media access control specification. 408 Annex G DOCS 2.0 and 1.0/1.1 interoperability 410 G.1 General interoperability issues . 410 G.2 Hybrid devices 413 G.3 DOCS 2.0 TDMA interoperability.
25、 414 G.4 DOCS 2.0 S-CDMA interoperability . 415 Annex H The DOCS MAC/PHY interface (DMPI) . 416 H.1 Scope 416 H.2 Conventions 416 H.3 Overview 417 H.4 Signals 420 H.5 Protocol. 423 H.6 Electrical specifications 428 H.7 Timing specifications . 428 H.8 Data format and usage 430 Annex I (Set aside) 438
26、 Annex J Japan specification additions 438 J.1 Scope and purpose 438 J.2 References 438 J.3 Glossary 438 J.4 Functional assumptions 438 J.5 Communication protocols 442 J.6 Physical media dependent sublayer specification 442 J.7 Downstream transmission convergence sublayer. 465 J.8 Media access contr
27、ol specification. 465 J.9 Media access control protocol operation 466 J.10 Quality of service and fragmentation . 467 J.11 Cable modem CMTS interaction. 467 J.C Common radio frequency interface encodings. 467 J.E The data-over-cable spanning tree protocol . 468 vi Rec. ITU-T J.122 (12/2007) Page App
28、endix I MAC service definition 469 I.1 MAC service overview. 469 I.2 MAC data service interface 471 I.3 MAC control service interface . 473 I.4 MAC service usage scenarios. 476 Appendix II Example preamble sequence 477 II.1 Introduction 477 II.2 Example preamble sequence 477 Appendix III Multiple up
29、stream channels 479 III.1 Single downstream and single upstream per cable segment 479 III.2 Multiple downstreams and multiple upstreams per cable segment 481 Appendix IV DOCS transmission and contention resolution . 485 IV.1 Introduction 485 IV.2 Variable definitions 486 IV.3 State examples 487 IV.4
30、 Function examples 488 Appendix V IGMP example . 490 V.1 Events . 490 V.2 Actions 491 Appendix VI Unsolicited grant services . 492 VI.1 Unsolicited grant service (UGS) 492 VI.2 Unsolicited grant service with activity detection (UGS-AD). 494 Appendix VII S-CDMA framing 498 VII.1 Coded subsymbol numbe
31、ring. 498 VII.2 Uncoded subsymbol numbering. 498 VII.3 Framer output numbering. 499 VII.4 Comments. 499 Appendix VIII Ambient temperature and wind loading effects . 500 VIII.1 Synchronization tolerances to plant delay variations . 500 VIII.2 Change in propagation delay due to temperature changes . 5
32、01 Bibliography. 503 Rec. ITU-T J.122 (12/2007) 1 Recommendation ITU-T J.122 Second-generation transmission systems for interactive cable television services IP cable modems 1 Scope and purpose 1.1 Scope This Recommendation defines the second generation of radio-frequency interface specifications fo
33、r high-speed data-over-cable systems. There are differences in the cable spectrum planning practices adopted for different networks in the world. Therefore, three options for physical layer technology are included, which have equal priority and are not required to be interoperable. One technology op
34、tion is based on the downstream multi-programme television distribution that is deployed using 6 MHz channelling, and supports upstream transmission in the 5-42 MHz region. The second technology option is based on a multi-programme television distribution using 8 MHz channel spacing and supports ups
35、tream in the 5-65 MHz region. The third technology option is based on 6 MHz channel spacing and supports upstream in the 10-55 MHz region. All options have equal status. The first of these options is defined in clauses 4, 6 and 7, whereas the second and third are defined by replacing the content of
36、those clauses with the content of Annex F or Annex J. Compliance with this Recommendation requires compliance with only one of these implementations. It is not required that equipment built to one option shall interoperate with equipment built to another. These optional physical-layer technologies a
37、llow operators some flexibility within any frequency planning, EMC and safety requirements that are mandated for their area of operation. For example, the 6 MHz downstream-based option defined by clauses 4, 6 and 7 might be deployable within an 8 MHz channel plan. Frequency planning, safety and EMC
38、requirements are a national matter and are not covered by this Recommendation. Compliance remains the operators responsibility. All optional physical-layer technologies are required to be backwards compatible with the earlier versions of those options defined in DOCS9, DOCS11 and DOCS12. NOTE The st
39、ructure 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. 1.2 Requirements If this Recommendation is implemented, the key words “MUST“ and “SHALL“ as well
40、 as “REQUIRED“ are to be interpreted as indicating a mandatory aspect of this Recommendation. The keywords indicating a certain level of significance of a particular requirement that are used throughout this Recommendation are summarized below. MUST This word or the adjective “REQUIRED“ means that t
41、he 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“ means that there may exist valid reasons in particular circumstances to ignore this item, but the ful
42、l implications 2 Rec. ITU-T J.122 (12/2007) 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 when the listed behaviour is acceptable or even useful, but the full implica
43、tions 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 to include the item because a particular marketplace requires it or because i
44、t enhances the product, for example; another vendor may omit the same item. This Recommendation defines many features and parameters, and a valid range for each parameter is usually specified. Equipment (CM and CMTS) requirements are always explicitly stated. Equipment must comply with all mandatory
45、 (MUST and MUST NOT) requirements to be considered compliant with this Recommendation. Support of non-mandatory features and parameter values is optional. 1.3 Background 1.3.1 Service goals As cable operators have widely deployed high-speed data services on cable television systems, the demand for u
46、pstream bandwidth has increased, particularly with the popularity of more symmetric data applications. The current Recommendation has been created for the purpose of increasing channel capacity and improving noise immunity. The intended service will allow transparent bidirectional transfer of Intern
47、et protocol (IP) traffic, between the cable system headend and customer locations, over an all-coaxial or hybrid-fibre/coax (HFC) cable network. This is shown in simplified form in Figure 1-1. Figure 1-1 Transparent IP traffic through the data-over-cable system The transmission path over the cable s
48、ystem is realized at the headend by a cable modem termination system (CMTS), and at each customer location by a cable modem (CM). At the headend (or hub), the interface to the data-over-cable system is called the cable modem termination system-network side interface (CMTS-NSI). At the customer locat
49、ions, the interface is called the cable-modem-to-customer-premises-equipment interface (CMCI). The intent is for operators to transparently transfer IP traffic between these interfaces, including but not limited to datagrams, DHCP, ICMP and IP group addressing (broadcast and multicast). 1.3.2 Reference architecture The reference architecture for the data-over-cable services and interfaces is shown in Figure 1-2. 3 Rec. ITU-T J.122 (12/2007) J.122_F1-2Distribution hub or headendOperations support systemCustomerpremisesequipmentCable m
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