1、 International Telecommunication Union ITU-T T.127TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (08/2007) SERIES T: TERMINALS FOR TELEMATIC SERVICES Data protocols for multimedia conferencing Multipoint binary file transfer protocol ITU-T Recommendation T.127 ITU-T T-SERIES RECOMMENDATIONS TERMINA
2、LS FOR TELEMATIC SERVICES Facsimile Framework T.0T.19 Still-image compression Test charts T.20T.29 Facsimile Group 3 protocols T.30T.39 Colour representation T.40T.49 Character coding T.50T.59 Facsimile Group 4 protocols T.60T.69 Telematic services Framework T.70T.79 Still-image compression JPEG-1,
3、Bi-level and JBIG T.80T.89 Telematic services ISDN Terminals and protocols T.90T.99 Videotext Framework T.100T.109 Data protocols for multimedia conferencing T.120T.149 Telewriting T.150T.159 Multimedia and hypermedia framework T.170T.189 Cooperative document handling T.190T.199 Telematic services I
4、nterworking T.300T.399 Open document architecture T.400T.429Document transfer and manipulation T.430T.449 Document application profile T.500T.509 Communication application profile T.510T.559 Telematic services Equipment characteristics T.560T.649 Still-image compression JPEG 2000 T.800T.849 Still-im
5、age compression JPEG-1 extensions T.850T.899 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. T.127 (08/2007) i ITU-T Recommendation T.127 Multipoint binary file transfer protocol Summary ITU-T Recommendation T.127 defines a protocol to support the interchange of bi
6、nary file data within an interactive conferencing or group working environment where the T.120 suite of standards is in use. It provides mechanisms to support simultaneous distribution of multiple files, selective distribution of files to a subset of participants and retrieval of files from remote s
7、ites. Provision is also made for remote directory access. This revised version of T.127 introduces a number of clarifications to the previous version. Source ITU-T Recommendation T.127 was approved on 29 August 2007 by ITU-T Study Group 16 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii
8、 ITU-T Rec. T.127 (08/2007) 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, operati
9、ng 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 groups which, in turn, prod
10、uce 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 ISO and IEC. NOTE In thi
11、s 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 provisions (to ensure e.g., int
12、eroperability 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
13、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 concerning the evidence
14、, 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 patents, which may b
15、e 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 2008 All rights reserved. No part of this publication may be re
16、produced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. T.127 (08/2007) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations 3 5 Introduction to multipoint file transfer . 3 6 Multipoint transfer of data An overview . 4 6.1 T.127 system model
17、 6 6.2 Compression. 7 6.3 Priority 7 6.4 File preshipping 7 7 Baseline MBFT application 7 8 Description of operation . 8 8.1 File transfer user application 8 8.2 File Transfer Application Resource Manager 9 8.3 File Transfer Application Service Element 9 8.4 MBFT resources . 10 8.5 MBFT capabilities
18、 20 8.6 Support of additional concurrent file transfers. 22 8.7 Selective file transfer 23 8.8 Leaving an MBFT session 24 8.9 File exchange 24 8.10 Remote directory listing . 31 8.11 Conducted mode behaviour 31 8.12 Aborting a file transfer . 34 8.13 Diagnostics . 34 8.14 Non-standard operations. 35
19、 9 MBFT PDU Definitions . 35 10 Use of the Multipoint Communication Service 43 10.1 Use of MCS data transmission services . 43 10.2 Channel allocation 43 10.3 Token allocation . 44 10.4 MCS services 45 11 Use of Generic Conference Control . 46 11.1 Resource IDs 47 iv ITU-T Rec. T.127 (08/2007) Page
20、Annex A Static channel and token assignment. 49 Annex B Object Identifier assignments 50 Appendix I File Transfer Examples 51 Appendix II MBFT attributes . 57 ITU-T Rec. T.127 (08/2007) 1 ITU-T Recommendation T.127 Multipoint binary file transfer protocol 1 Scope This Recommendation defines a protoc
21、ol to support the interchange of binary files within an interactive conferencing or group working environment where the T.120 suite of standards is in use. It provides mechanisms which facilitate distribution and retrieval of one or more files simultaneously using the primitives provided by ITU-T T.
22、122 (Multipoint Communications Service). This Recommendation is designed to offer a versatile, light weight protocol which provides the core functionality to allow interworking between applications requiring a basic file transfer capability and also has the flexibility to meet the demands of more so
23、phisticated applications. See Figure 1. 2 References The following ITU-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
24、 other references are subject to revision; users of this Recommendation 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. Th
25、e reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T H.221 ITU-T Recommendation H.221 (2004), Frame structure for a 64 to 1920 kbit/s channel in audiovisual teleservices. ITU-T T.35 ITU-T Recommendation T.35 (2000), P
26、rocedure for the allocation of ITU-T defined codes for non-standard facilities. ITU-T T.120 ITU-T Recommendation T.120 (2007), Data Protocols for multimedia conferencing. ITU-T T.122 ITU-T Recommendation T.122 (1998), Multipoint communication service Service definition. ITU-T T.123 ITU-T Recommendat
27、ion T.123 (2007), Network-specific data protocol stacks for multimedia conferencing. ITU-T T.124 ITU-T Recommendation T.124 (2007), Generic Conference Control. ITU-T T.125 ITU-T Recommendation T.125 (1998), Multipoint communication service protocol specification. ITU-T T.434 ITU-T Recommendation T.4
28、34 (1999), Binary file transfer format for the telematic services. ITU-T V.42 bis ITU-T Recommendation V.42 bis (1990), Data compression procedures for data circuit-terminating equipment (DCE) using error correction procedures. ITU-T X.680 ITU-T Recommendation X.680 (2002), Information technology Ab
29、stract Syntax Notation One (ASN.1) Specification of basic notation. ITU-T X.691 ITU-T Recommendation X.691 (2002), Information technology ASN.1 encoding rules: Specification of Packed Encoding Rules (PER). 2 ITU-T Rec. T.127 (08/2007) ISO/IEC 13239 ISO/IEC 13239:2002, Information technology Telecomm
30、unications and information exchange between systems High-Level Data Link Control (HDLC) procedures. ISO 8571-2 ISO 8571-2:1988, Information processing systems Open Systems Interconnection File Transfer, Access and Management (FTAM) Part 2: Virtual filestore definitions. Figure 1 Scope of T.127 3 Def
31、initions This Recommendation defines the following terms: 3.1 acknowledged data channel: An MCS channel on which files are distributed. Participants have the option of rejecting files offered on an acknowledged data channel. An acknowledged data channel may be exclusive (i.e., only the channel creat
32、or may send files on it), or shared (any participant may send files on it). 3.2 broadcast data channel: An MCS channel on which files are distributed. Participants must receive all files distributed on the channel, discarding the data locally if it is not required. 3.3 control channel: An MCS channe
33、l used for the management of file transactions. 3.4 file attributes: The name and other identifiable properties of a file. 3.5 FILE-REQUEST: The token used to ensure that there is at most one outstanding file request on the session control channel MBFT-CONTROL. ITU-T Rec. T.127 (08/2007) 3 3.6 FILE-
34、REQUEST(p): The token used to ensure that there is at most one outstanding file request on the sub-session control channel MBFT-CONTROL(p). 3.7 FILE-TRANSMIT: The token used to ensure that there is at most one file transfer in progress on the session broadcast data channel MBFT-DATA. 3.8 FILE-TRANSM
35、IT(p): The token used to ensure that there is at most one file transfer in progress on the sub-session broadcast data channel MBFT-DATA(p). 3.9 FILE-TRANSMIT(n): The token used to ensure that there is at most one file transfer in progress on acknowledged data channel MBFT-DATA(n). 3.10 MBFT-CONTROL:
36、 The session control channel. 3.11 MBFT-CONTROL(p): A sub-session control channel, whose MCS Channel ID is p. 3.12 MBFT-DATA: The session broadcast data channel. 3.13 MBFT-DATA(p): A sub-session broadcast data channel, whose MCS Channel ID is p. 3.14 MBFT-DATA(n): An acknowledged data channel, whose
37、 MCS Channel ID is n. 3.15 non-standard capability: A capability that is outside the scope of this Recommendation. Non-standard capabilities must be negotiated before use. 3.16 session: A set of peer Application Protocol Entities. 3.17 standard capability: A capability that is defined within the sco
38、pe of this Recommendation, but is not required for all MBFT implementations. Standard capabilities must be negotiated before use. 3.18 sub-session: A sub-group of peer Application Protocol Entities within a session. 4 Abbreviations This Recommendation uses the following abbreviations: ARM Applicatio
39、n Resource Manager APE Application Protocol Entity ASE Application Service Element GCC Generic Conference Control GCCSAP GCC Service Access Point MBFT Multipoint Binary File Transfer MCS Multipoint Communication Service MCSAP MCS Service Access Point PDU Protocol Data Unit 5 Introduction to multipoi
40、nt file transfer In order to support group activities such as meetings, conferences, etc. involving physically separated participants, there is a requirement to join together two or more locations. The term multipoint communication simply describes the interconnection of multiple terminals. Multipoi
41、nt Binary File Transfer (MBFT) enables files to be exchanged interactively between participants within a multipoint environment through use of the underlying network independent Multipoint Communication Service (MCS). 4 ITU-T Rec. T.127 (08/2007) Specifically, this Recommendation provides flexible a
42、nd efficient mechanisms to support: Simultaneous distribution of multiple files. Broadcasting of files to all participants within a conference. Selective distribution of files to a subset of participants. Retrieval of files from remote sites. Partial retransmission of files following an interruption
43、. Remote directory access. 6 Multipoint transfer of data An overview T.127 uses a control/data channel architecture to facilitate simultaneous transfer of one or more binary files. It enables files to be broadcast to all participants within a conference, or to be directed selectively to a subset of
44、sites as a private file transfer. No restrictions are placed on the type of data being transmitted. Two types of channels are used within T.127; control channels and data channels. Control channels are used for managing all aspects of the file transfer (offering files, requesting files), whereas dat
45、a channels are used exclusively for the transfer of file data. Only one file can be transmitted on each data channel at a time, but additional data channels can be used to allow distribution of multiple files simultaneously. The number of data channels in use at any given time depends on the number
46、of concurrent file transfers in progress. A group of file transfer applications communicating with each other are said to be participating in the same file transfer session. Each file transfer session requires a single control channel and one or more data channels for distribution of files to all pa
47、rticipating applications. T.127 supports two types of data channel: broadcast and acknowledged. If a transmitter wishes to mandate that all nodes receive a file it is offering, then it should use the broadcast data channel. All nodes must stay joined to the broadcast data channel for the duration of
48、 the file transfer session and are obliged to receive all files distributed on it; if a file is not required, receivers should discard it. If a transmitter wishes to give other nodes the option of rejecting a file, it should offer the file on an acknowledged data channel. In this case, each node mus
49、t inform the transmitter of whether it requires the data or not, and only those which want the file join the data channel. Multiple concurrent file transfers are supported by use of acknowledged data channels. Acknowledged data channels should be used if a transmitter considers that one or more of the parameters in the file header are essential to the operation of the application. For example, an application may require a pathname to be preserved by receivers for future ref
