1、 International Telecommunication Union ITU-T J.292 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2006) SERIES J: CABLE NETWORKS AND TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Cable modems Next generation set-top box media-independent architecture ITU-T Recommendat
2、ion J.292 ITU-T Rec. J.292 (11/2006) i ITU-T Recommendation J.292 Next generation set-top box media-independent architecture Summary This Recommendation describes a core architecture that is not dependent on transport media for a next generation set-top box that will allow service providers to offer
3、 existing and new advanced services regardless of the transport media in the future. It is assumed in this Recommendation that all contents are transported on IP packets with an adequate QoS controlled mechanism. This Recommendation reflects key functional aspects of the next generation set-top box,
4、 such as network resource adaptability, secure two-way authenticated communication and session resource management and a QoS-control mechanism. Source ITU-T Recommendation J.292 was approved on 29 November 2006 by ITU-T Study Group 9 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T
5、 Rec. J.292 (11/2006) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and
6、 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 groups which, in turn, produce Re
7、commendations 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 Reco
8、mmendation, 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. interopera
9、bility 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 words does not suggest that co
10、mpliance 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 concerning the evidence, valid
11、ity 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 patents, which may be requi
12、red 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 2007 All rights reserved. No part of this publication may be reproduce
13、d, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. J.292 (11/2006) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 4 Abbreviations and acronyms 2 5 Conventions 3 6 Next generation STB architecture on media-independent environment. 4 6.1 Reference architec
14、ture 4 6.2 Attributes of next generation STB for media-independent environment . 5 7 Customer premises 7 7.1 Functionality of CPE devices . 7 7.2 Protocol architecture of video transport and data applications 8 7.3 Signalling protocol between CPE and CDN segments. 9 7.4 Linkage between multicast flo
15、w and TS 9 7.5 Packet loss recovery . 9 7.6 TS-clock synchronization. 10 7.7 Zapping control 10 7.8 Location awareness 11 8 IP multicasting 11 8.1 IP multicasting 11 8.2 IGMP 11 8.3 IGMP snooping 12 8.4 Multicast routing protocol 12 9 QoS priority and policy mapping . 12 9.1 QoS priority 12 9.2 QoS
16、policy mapping. 15 10 IP broadcast and channel switching point 16 BIBLIOGRAPHY 17 ITU-T Rec. J.292 (11/2006) 1 ITU-T Recommendation J.292 Next generation set-top box media-independent architecture 1 Scope This Recommendation describes the core architecture of a next generation STB that is not depend
17、ent on the transport media. Operators and equipment vendors MAY elect to follow in making network and product investment decisions. This architecture specifically defines network resource adaptability, secure two-way authenticated communication and session resource management and QoS-control mechani
18、sm over full-IP environments. This architecture is applicable to support the growth of on-demand video, high-definition digital TV, managed in-home networks connecting a wide range of consumer-provided devices, and IP multimedia services including IP voice, video telephony, and multiplayer gaming. T
19、he goal of this Recommendation is to provide core functionalities for next generation STB regardless of the transport media. In actual implementation of NG-STB-A functionalities, the Recommendation MUST be used with ITU-T J.290. This Recommendation contains some technical solutions as examples to he
20、lp the readers understanding, not for the specification for the media-independent STB. It should be noted that the future Recommendations will define technical solutions relevant to the media- independent STB. 2 References None. 3 Definitions This Recommendation defines the following terms: 3.1 cont
21、ent distribution network (CDN): CDN contains a Core network and Access network where content delivery is controlled by identified packet routing and a QoS oriented mechanism. 3.2 customer premises equipment (CPE): CPE covers subscriber video devices (SVD), residential gateway (RGW), and optional in-
22、home networking devices. 3.3 IP multicast: It is used for IP broadcasting in terms of bandwidth use efficiency of headend, CDN (Content Distribution Network), and CPE segment. 3.4 2-way authenticated communication channels: These channels are used for renewable conditional access key management, rem
23、ote management of SVD, downloadable firmware updates, private interactive application data, and reconfiguration of encryption algorithms between the headend and an SVD. 3.5 transport stream (TS): The transport stream described in this Recommendation is delivered using a certain multicast flow, which
24、 is identified by multicast group address, UDP port number, etc. 3.6 portal services (PS): A functional element that provides management and translation functions between the HFC and Home network. 3.7 zapping control: The control mechanism for multicast group join and leave considering the IGMP/MLD
25、protocol sequence is required in NG-STB compliant CPE devices. 3.8 residential gateway: The device that provides interconnection functionalities between access network and home network as described in b-ITU-T J.190. NOTE How to apply J.190 residential gateway functionality to various networks SHOULD
26、 be considered in the near future. 2 ITU-T Rec. J.292 (11/2006) 4 Abbreviations and acronyms This Recommendation uses the following abbreviations: ARQ Automatic Repeat ReQuest BE Best Effort BGP Border Gateway Protocol CA Conditional Access CAS Conditional Access System CDN Content Distribution Netw
27、ork (in terms of the definition in b-ITU-T J.282) CoS Class of Service CPE Customer Premises Equipment DB Database DHCP Dynamic Host Configuration Protocol DiffServ Differentiated Services Architecture for Network Traffic DOCSIS Data over Cable Service Interface Specification DSCP DiffServ Code Poin
28、t DSLAM Digital Subscriber Line Access Multiplexer DTV Digital Television EMM Entitlement Management Message FEC Forward Error Correction GigE Gigabit Ethernet HDTV High-definition Television HE Headend HGW Home Gateway IGMP Internet Group Management Protocol IP Internet Protocol Layer 3 Network lay
29、er 3 in OSI stack LDPC Low-Density Parity Check MAC Media Access Control MLD Multicast Listener Discovery MPEG Motion Picture Experts Group NAT Network Address Translation NG-STB Next Generation Set-Top Box NG-STB-MI-A Next Generation Set-Top Box Media-Independent Architecture NIT Network Informatio
30、n Table OLT Optical Line Terminal OSPF Open Shortest Path First PCR Program Clock Reference ITU-T Rec. J.292 (11/2006) 3 PID Packet Identifier PIMSM Protocol Independent Multicast Sparse Mode QoS Quality of Service RGW Residential Gateway RTP Real Time Protocol RTSP Real-Time Streaming Protocol SI S
31、ervice Information STB Set-Top Box SVD Subscriber Video Device TCP Transmission Control Protocol TLS Transport Layer Security ToS Type of Service TS Transport Stream UPnP Universal Plug and Play VCO Voltage-Controlled Oscillator VoD Video on Demand VoIP Voice over Internet Protocol 5 Conventions Thr
32、oughout this Recommendation words that are used to define the significance of particular requirements 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
33、 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 full implications should be understood and the case carefully weighed before choosing a different course.
34、“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 implications should be understood and the case carefully weighed before implementing any behaviour described with this label. “MAY“ This
35、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 it enhances the product, for example; another vendor may omit the same item. 4 ITU-T Rec. J.292 (11/2006) 6 Next generation STB a
36、rchitecture on media-independent environment In addition to clause 6 of ITU-T J.290, the following items are mandatory key attributes of the next generation STB (NGSTB) architecture for a media-independent IP network environment: Network resource adaptability. Enables the network operator to utilize
37、 network bandwidth more efficiently through the use of: packet loss recovery schemes; residual traffic suppression caused by channel zapping; unified end-to-end QoS management from the headend to a subscriber video device (SVD) compliant with NGSTB media-independent architecture (NG-STB-MI-A); toget
38、her with the advanced audio/video codec described in ITU-T J.290. MPEG-2 TS transfer over IP. Enables the network operator to distribute transport streams in a media-independent environment through the use of a standard Internet Protocol suite with stream description information specified for IP mul
39、ticast. Resilient TS-clock synchronization with headend. Enables all NG-STB-MI-A compliant SVDs to avoid play-out buffer overrun and underrun over the IP network environment. Common presentation engine. Enables an NG-STB-MI-A compliant SVD to support presentation engines defined in b-ITU-T J.200 and
40、 b-ITU-T J.201. Location awareness. Enables the network operator to control the distribution area of the transport stream based on the location of SVDs. SVD location awareness is optionally required. Secure two-way authenticated channels via IP network. Transport Layer Security (TLS) 1.0 in an NG-ST
41、B-MI-A compliant SVD provides secure 2-way authenticated communication channels between the headend and an SVD. Such channels are used for renewable conditional access key management, remote management of SVD, downloadable firmware updates, private interactive application data, and reconfiguration o
42、f encryption algorithms. 6.1 Reference architecture The reference architecture of an IP content distribution service infrastructure is diagrammed in Figure 1. The relationship among major network segments is also summarized, e.g., CPE (customer premises equipment) including subscriber video device (
43、SVD) and in-home network devices such as residential gateway (RGW), content delivery network (CDN) that MAY be separately defined as core and metro networks, Internet, and headend (HE). In a media-independent environment, all content distribution services are provided by an IP unicast or multicast t
44、ransmission bearer. IP multicast SHOULD be used for IP broadcasting in terms of bandwidth efficiency of headend, CDN, and CPE segment. ITU-T Rec. J.292 (11/2006) 5 Figure 1 Reference architecture of IP content distribution service infrastructure 6.2 Attributes of next generation STB for media-indepe
45、ndent environment 6.2.1 Content distribution services architecture At a minimum, NG-STB-MI-A SHOULD have the following attributes in addition to clause 6.2.1 of ITU-T J.290. IP-based content distribution. IP is selected as the basic bearer layer for all content distribution services. All NG-STB-MI-A
46、-compliant devices are required to support IPv4 with future IPv6 upgradeability. IPv4/v6 dual stack is also possible to use. Auto configuration mechanisms such as DHCP are also required for providing IP connectivity without manual configuration effort. Linkage between multicast flow and TS. The tran
47、sport stream is delivered using a certain multicast flow, which is identified by multicast group address, UDP port number, etc. It is recommended to assign a different group address to each transport stream. All NG-STB-MI-A-compliant SVDs are required to obtain multicast flow information correspondi
48、ng to the transport stream that the SVD wants to play out. Zapping control. The control mechanism is required in NG-STB-MI-A-compliant CPE devices for content zapping scenarios, where SVD consecutively changes multicast groups (i.e., transport streams) at high speed. As a result, residual traffic fr
49、om groups having already left MAY cause congestion in the CPE segment. Packet loss recovery. In order to enforce transmission quality of the transport stream (TS), all NG-STB-MI-A-compliant SVDs are required to support packet loss recovery mechanism. TS-clock synchronization. In order to synchronize audio/video play-out timing with the encoder in the headend segment, a robust TS-clock regeneration mechanism is required even if there is some packet arrival jitter and/or losses of packet with Program Clock Reference (PCR) information in the IP trans
