1、 ETSI TS 102 606 V1.1.1 (2007-10)Technical Specification Digital Video Broadcasting (DVB);Generic Stream Encapsulation (GSE) ProtocolEuropean Broadcasting Union Union Europenne de Radio-Tlvision EBUUER ETSI ETSI TS 102 606 V1.1.1 (2007-10) 2 Reference DTS/JTC-DVB-213 Keywords DVB, broadcasting ETSI
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6、 The copyright and the foregoing restriction extend to reproduction in all media. European Telecommunications Standards Institute 2007. European Broadcasting Union 2007. All rights reserved. DECTTM, PLUGTESTSTM and UMTSTM are Trade Marks of ETSI registered for the benefit of its Members. TIPHONTMand
7、 the TIPHON logo are Trade Marks currently being registered by ETSI for the benefit of its Members. 3GPPTM is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners. ETSI ETSI TS 102 606 V1.1.1 (2007-10) 3 Contents Intellectual Property Rights4 Forewor
8、d.4 1 Scope 5 2 References 6 2.1 Normative references .6 2.2 Informative references6 3 Abbreviations .7 4 Generic Stream Encapsulation (GSE) Protocol7 4.1 GSE Principles .7 4.1.1 PDU Fragmentation and Reassembly .8 4.1.2 Network Protocol Identification .9 4.1.3 Addressing and Hardware Filtering 9 4.
9、1.4 Locating GSE Streams9 4.1.5 Transporting Signalling Information 9 4.2 GSE Packet Format 10 4.2.1 Specification .10 4.2.2 CRC-32 Trailer .12 4.3 PDU Fragmentation13 5 Labels: Addresses and Binding 15 6 GSE SI specifications.16 Annex A (normative): Receiver Processing .17 A.1 Filtering 17 A.2 Reas
10、sembly.17 A.3 Protocol Type and Next Header Processing.18 A.4 Label re-use18 A.5 Padding.18 Annex B (informative): Encapsulator Processing .19 B.1 Encapsulator/Scheduler Functions .19 B.2 Use of the Label Type Indicator.21 Annex C (informative): GSE Packet Format Examples .22 Annex D (informative):
11、Bibliography.24 History 25 ETSI ETSI TS 102 606 V1.1.1 (2007-10) 4 Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-m
12、embers, and can be found in ETSI SR 000 314: “Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect of ETSI standards“, which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web server (http:/webapp.etsi.org/IPR/ho
13、me.asp). Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to th
14、e present document. Foreword This Technical Specification (TS) has been produced by Joint Technical Committee (JTC) Broadcast of the European Broadcasting Union (EBU), Comit Europen de Normalisation ELECtrotechnique (CENELEC) and the European Telecommunications Standards Institute (ETSI). NOTE: The
15、EBU/ETSI JTC Broadcast was established in 1990 to co-ordinate the drafting of standards in the specific field of broadcasting and related fields. Since 1995 the JTC Broadcast became a tripartite body by including in the Memorandum of Understanding also CENELEC, which is responsible for the standardi
16、zation of radio and television receivers. The EBU is a professional association of broadcasting organizations whose work includes the co-ordination of its members activities in the technical, legal, programme-making and programme-exchange domains. The EBU has active members in about 60 countries in
17、the European broadcasting area; its headquarters is in Geneva. European Broadcasting Union CH-1218 GRAND SACONNEX (Geneva) Switzerland Tel: +41 22 717 21 11 Fax: +41 22 717 24 81 Founded in September 1993, the DVB Project is a market-led consortium of public and private sector organizations in the t
18、elevision industry. Its aim is to establish the framework for the introduction of MPEG-2 based digital television services. Now comprising over 200 organizations from more than 25 countries around the world, DVB fosters market-led systems, which meet the real needs, and economic circumstances, of th
19、e consumer electronics and the broadcast industry. ETSI ETSI TS 102 606 V1.1.1 (2007-10) 5 1 Scope The present document includes the definition of the Generic Stream Encapsulation (GSE) protocol, which allows for efficient encapsulation of IP and other network layer packets over a “generic“ physical
20、 layer. Such a “generic“ physical layer is intended as a transport mode that carries a sequence of data bits or data packets, possibly organized in frames, but with no specific timing constraints. The first generation of DVB standards only supported data transport using the MPEG format (see ISO/IEC
21、13818-1 2), with a Transport Stream packet multiplex (MPEG-TS). Multi Protocol Encapsulation (EN 301 192 3) is the DVB standard for encapsulation of audio/video and other content on MPEG-TS packets. The second generation of DVB standards features backwards compatibility modes for carrying MPEG-TS as
22、 well as generic modes for carrying arbitrary packets of variable length. These are referred to as Generic Streams (GS). The GSE protocol has been devised as an adaptation layer to provide network layer packet encapsulation and fragmentation functions over Generic Stream. GSE provides efficient enca
23、psulation of IP datagrams over variable length Layer 2 packets, which are then directly scheduled on the physical layer into Base Band frames. GSE maximizes efficiency of IP datagrams transport reducing overhead by a factor 2 to 3 with respect to MPE over MPEG-TS. This is achieved without any compro
24、mise of the functionalities provided by the protocol, due to the variable length Layer 2 packet size, suited to IP traffic characteristics. For example in an interactive DVB-S2 system, the overhead is reduced on average from about 10 % for MPE/MPEG-TS to 2 % to 3 % for GSE. Hence yielding an overall
25、 throughput gain of about 5 % to 15 %, the actual benefit is of course dependent on the concrete system and traffic characteristics. In addition to the overhead reduction, GSE provides a more efficient system operation for interactive systems that utilize advanced physical layer techniques such as f
26、or instance Adaptive Coding and Modulation (ACM). The inherent channel rate variability experienced in ACM systems makes the Generic Stream format more suited than the Transport Stream. GSE provides a flexible fragmentation and encapsulation method, which permits use of a smart scheduler to optimize
27、 system performance, either by increasing the total throughput and/or by improving the average packet end-to-end delay. In addition, GSE flexibility leads to a reduction in packet loss under fading variations, allowing the scheduler at the transmitter to dynamically change transmission parameters (f
28、or example modulation format, coding rate) for a particular network layer packet. GSE also provides additional features that increase the protocol flexibility and applicability. Some key GSE functions/characteristics are: 1) Support for multi-protocol encapsulation (IPv4, IPv6, MPEG, ATM, Ethernet,
29、802.1pQ VLANs, etc.). 2) Transparency to network layer functions, including IP encryption and IP header compression. 3) Support of several addressing modes: In addition to the 6-byte MAC address (including multicast and unicast), it supports a MAC addressless mode, and an optional 3-byte address mod
30、e. 4) A mechanism for fragmenting IP datagrams or other network layer packets over Base Band frames to support ACM/VCM. 5) Support for hardware filtering. 6) Extensibility: additional link protocols can be included through specific protocol type values (e.g. Layer 2 security, IP Header Compression,
31、etc.). 7) Low complexity. ETSI ETSI TS 102 606 V1.1.1 (2007-10) 6 2 References References are either specific (identified by date of publication and/or edition number or version number) or non-specific. For a specific reference, subsequent revisions do not apply. Non-specific reference may be made o
32、nly to a complete document or a part thereof and only in the following cases: - if it is accepted that it will be possible to use all future changes of the referenced document for the purposes of the referring document; - for informative references. Referenced documents which are not found to be pub
33、licly available in the expected location might be found at http:/docbox.etsi.org/Reference. For online referenced documents, information sufficient to identify and locate the source shall be provided. Preferably, the primary source of the referenced document should be cited, in order to ensure trace
34、ability. Furthermore, the reference should, as far as possible, remain valid for the expected life of the document. The reference shall include the method of access to the referenced document and the full network address, with the same punctuation and use of upper case and lower case letters. NOTE:
35、While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guarantee their long term validity. 2.1 Normative references The following referenced documents are indispensable for the application of the present document. For dated references, only the edition cited a
36、pplies. For non-specific references, the latest edition of the referenced document (including any amendments) applies. 1 ETSI EN 302 307: “Digital Video Broadcasting (DVB); Second generation framing structure, channel coding and modulation systems for Broadcasting, Interactive Services, News Gatheri
37、ng and other broadband satellite applications“. 2 ISO/IEC 13818 (parts 1 and 2): “Information technology - Generic coding of moving pictures and associated audio information“. 3 ETSI EN 301 192: “Digital Video Broadcasting (DVB); DVB specification for data broadcasting“. 4 IETF RFC 4326: “Unidirecti
38、onal Lightweight Encapsulation (ULE) for Transmission of IP Datagrams over an MPEG-2 Transport Stream (TS)“. 5 IETF RFC 3819: “Advice for Internet Subnetwork Designers“. 6 IETF RFC 3309: “Stream Control Transmission Protocol (SCTP) Checksum Change“. 7 IETF RFC 1112: “Host extensions for IP multicast
39、ing“. 8 IETF RFC 2464: “Transmission of IPv6 Packets over Ethernet Networks“. 9 draft-ietf-ipdvb-ule-ext-04.txt: “Extension Formats for Unidirectional Lightweight Encapsulation (ULE) and the Generic Stream Encapsulation (GSE)“. 2.2 Informative references 10 ETSI TR 101 162: “Digital Video Broadcasti
40、ng (DVB); Allocation of Service Information (SI) codes for DVB systems“. ETSI ETSI TS 102 606 V1.1.1 (2007-10) 7 3 Abbreviations For the purposes of the present document, the following abbreviations apply: ACM Adaptive Coding and Modulation ATM Asynchronous Transfer Mode BB Base Band CRC Cyclic Redu
41、ndancy Check DVB Digital Video Broadcast E End indicator EBU European Broadcasting Union FragID Fragmentation Identifier GS Generic StreamGSE Generic Stream Encapsulation IANA Internet Assigned Numbers Authority IEEE Institute of Electrical and Electronics Engineers IETF Internet Engineering Task Fo
42、rce IP Internet Protocol IPR Intellectual Property Rights ISO International Standard Organization JTC Joint Technical Committee LT Label Type indicator MAC Medium Access Control MODCOD MODulation and CODing MPE Multi Protocol Encapsulation MPEG Moving Pictures Experts Group MPLS Multiple Protocol La
43、bel Switching NPA Network Point of Attachment PDU Protocol Data Unit QoS Quality of Service RCS Return Channel System RFC Request For Comment (IETF standard) S Start indicator SI Service Information TS Transport Stream ULE Unidirectional Lightweight Encapsulation VCI Virtual Channel Identifier VLAN
44、Virtual LAN VPI Virtual Path Identifier VCM Variable Coding and Modulation 4 Generic Stream Encapsulation (GSE) Protocol 4.1 GSE Principles Figure 1 illustrates GSE operation. IP datagrams, Ethernet Frames, or other network layer packets, herein named Protocol Data Units (PDUs), that are scheduled f
45、or transmission, are encapsulated in one or more GSE Packets. The encapsulation process delineates the start and end of each network-layer PDU, adds control information such as the network protocol type and address label, and provides an overall integrity check when needed. The PDU may be encapsulat
46、ed in a single GSE Packet or sliced into PDU fragments and encapsulated in several GSE Packets. GSE Packets have in general variable length, in order to match the input IP traffic with minimum overhead. GSE Packets may be sent in different Base Band frames, not necessarily consecutive or with the sa
47、me transmission parameters (modulation format, coding rate). Moreover, no constraint on the GSE Packet position within the frame is assumed. However, GSE Packets shall not be reordered between encapsulator and de-encapsulator. In general, a Base Band frame may multiplex more than a single GSE Packet
48、. Base Band frames may have fixed or variable length. ETSI ETSI TS 102 606 V1.1.1 (2007-10) 8 GSE does not include a mechanism for integrity check of single GSE Packets. A CRC-32 is only appended to the last PDU fragment of a fragmented PDU to verify the correctness of the reassembly operation. GSE
49、relies on the physical layer being able to ensure the required error detection and/or correction probability (see 5 for best current practices in IP networks). The present approach is independent of the specific physical layer provided that this meets the required level for error detection capability. Figure 1: GSE encapsulation within DVB protocol stack In a system where ACM is utilized, transmission parameters typically change dynamically on a frame-by-frame basis. A receiver will generally successfully decode only a subset of the transm
