1、 International Telecommunication Union ITU-T V.76TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Corrigendum 1(01/2005) SERIES V: DATA COMMUNICATION OVER THE TELEPHONE NETWORK Simultaneous transmission of data and other signals Generic multiplexer using V.42 LAPM-based procedures Corrigendum 1 ITU-T
2、 Recommendation V.76 (1996) Corrigendum 1 ITU-T V-SERIES RECOMMENDATIONS DATA COMMUNICATION OVER THE TELEPHONE NETWORK General V.1V.9 Interfaces and voiceband modems V.10V.34 Wideband modems V.35V.39 Error control V.40V.49 Transmission quality and maintenance V.50V.59 Simultaneous transmission of da
3、ta and other signals V.60V.99 Interworking with other networks V.100V.199 Interface layer specifications for data communication V.200V.249 Control procedures V.250V.299 Modems on digital circuits V.300V.399 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. V.76 (1996
4、)/Cor.1 (01/2005) i ITU-T Recommendation V.76 Generic multiplexer using V.42 LAPM-based procedures Corrigendum 1 Summary This corrigendum addresses corrections and clarifications in ITU-T Rec. V.76 (1996) concerning CRC calculation when using suspend/resume, N401 timer value and reuse of DLCI values
5、. Source Corrigendum 1 to ITU-T Recommendation V.76 (1996) was approved on 8 January 2005 by ITU-T Study Group 16 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. V.76 (1996)/Cor.1 (01/2005) FOREWORD The International Telecommunication Union (ITU) is the United Nations special
6、ized 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 tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a w
7、orldwide 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 Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down i
8、n 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, the expression “Administration“ is used for conciseness to indicate both a telecommunication adm
9、inistration 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 applicability) and compliance with the Recommendation is achieved when all of these mandatory prov
10、isions 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 with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention
11、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 applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outs
12、ide of the Recommendation development process. As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest
13、 information and are therefore strongly urged to consult the TSB patent database. ITU 2005 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. V.76 (1996)/Cor.1 (01/2005) iii CONTENTS Page 1) Clarificati
14、on of CRC calculation when using suspend/resume 1 2) Clarification of the N401 timer value. 1 3) Clarification on the reuse of DLCI values 2 ITU-T Rec. V.76 (1996)/Cor.1 (01/2005) 1 ITU-T Recommendation V.76 Generic multiplexer using V.42 LAPM-based procedures Corrigendum 1 1) Clarification of CRC c
15、alculation when using suspend/resume Amend clause 5.1.6.1 item b) to read: b) the remainder of the division (modulo 2) by the generator polynomial x8+ x2+ x + 1, of the product of x8by the content of the frame existing between, but not including, the final bit of the opening flag and the first bit o
16、f the FCS, excluding bits inserted for transparency and real-time frames as defined in Annex A (including the bits of the suspend and resume flags). Amend clause 5.1.6.2 item b) to read: b) the remainder of the division (modulo 2) by the generator polynomial x16+ x12+ x5+ 1, of the product of x16by
17、the content of the frame existing between, but not including, the final bit of the opening flag and the first bit of the FCS, excluding bits inserted for transparency and real-time frames as defined in Annex A (including the bits of the suspend and resume flags). Amend clause 5.1.6.3 item b) to read
18、: b) the remainder of the division (modulo 2) by the generator polynomial x32+ x26+ x23+ x22+ x16+ x12+ x11+ x10+ x8+ x7+ x5+ x4+ x2+ x + 1, of the product of x32by the content of the frame existing between, but not including, the final bit of the opening flag and the first bit of the FCS, excluding
19、 bits inserted for transparency and real-time frames as defined in Annex A (including the bits of the suspend and resume flags). 2) Clarification of the N401 timer value New text is added to the end of clause 9.3 (maximum number of octets in an information field (N401) as follows: N401 governs the m
20、aximum number of octets that can be carried in the information field of an I frame, an SREJ frame (m-SREJ procedure only), an XID frame, a UI frame, a UIH frame (see Appendix II), an SABME frame, a UA frame, a DISC frame, a DM frame, or a TEST frame transmitted by a data link connection entity. A de
21、fault value for a DLC may be expressed as a specific value (e.g., 128) or implied by certain characteristics pertaining to the operation of the DLC (e.g., the maximum size block associated with the coder selected for an audio channel). There may also be frame-specific maxima for a DLC that may apply
22、 for certain procedures (e.g., a maximum information-field size for UI frames different than the maximum for the SABME frame). This parameter consists of two subparameters one for each direction of transmission (i.e., a maximum information-field size in the direction from the DLC-opener to the remot
23、e station and a maximum from the remote station to the DLC-opener). Identical values need not be used for each direction. The value of N401 shall be in octets when signalled using H.245. 2 ITU-T Rec. V.76 (1996)/Cor.1 (01/2005) 3) Clarification on the reuse of DLCI values Amend clause 6.1.1 as follo
24、ws: The DLCI is used to identify an individual user information stream as well as to identify SU-to-SU connections. Multiple DLCIs shall be supported but the number is implementationapplication-specific. Selection of a new DLCI value shall be as follows.: a) The the initiator shall select DLCI value
25、s for new DLCs with increasing values starting from 0 DLCI values, originally chosen by the Initiator, that have been freed by either end should be reused in ascending order by Initiator rather than leaving unnecessary gaps in the numbering range.; b) Thethe responder shall select DLCI values for ne
26、w DLCs with decreasing values starting from from 63 when using one-octet address fields or 8191 when using two-octet address fields. DLCI values, originally chosen by the responder, that have been freed by either end should be reused in descending order by the responder rather than leaving unnecessa
27、ry gaps in the numbering range. The role of initiator and or responder shall be made known to the MF by the SU. The means of doing so is beyond the scope of this Recommendation. Use of the second address- field octet is optional. All DLC entities shall be able to receive frames with a two-octet addr
28、ess field. If a frame is received with an address field of a different type from the one negotiated, the receiving DLC entity shall ignore the frame. Regardless of role, DLCI values freed as a result of releasing a DLC shall be reused prior to new values being allocated. In case of collision (i.e.,
29、the same DLCI value being selected), the responder shall back off its attempt to establish a new DLC (i.e., it shall inform its SU of failure to establish the DLC it attempted and continue with the DLC establishment attempt by the initiator). Note that the procedures described above are intended to
30、reduce the probability of collisions occurring. The DLCI used on a given DLC is mapped to/from an internal “connection endpoint identifier”“ for communication between the MF and the SU. Printed in Switzerland Geneva, 2005 SERIES OF ITU-T RECOMMENDATIONS Series A Organization of the work of ITU-T Ser
31、ies D General tariff principles Series E Overall network operation, telephone service, service operation and human factors Series F Non-telephone telecommunication services Series G Transmission systems and media, digital systems and networks Series H Audiovisual and multimedia systems Series I Inte
32、grated services digital network Series J Cable networks and transmission of television, sound programme and other multimedia signals Series K Protection against interference Series L Construction, installation and protection of cables and other elements of outside plant Series M Telecommunication ma
33、nagement, including TMN and network maintenance Series N Maintenance: international sound programme and television transmission circuits Series O Specifications of measuring equipment Series P Telephone transmission quality, telephone installations, local line networks Series Q Switching and signall
34、ing Series R Telegraph transmission Series S Telegraph services terminal equipment Series T Terminals for telematic services Series U Telegraph switching Series V Data communication over the telephone network Series X Data networks, open system communications and security Series Y Global information infrastructure, Internet protocol aspects and next-generation networks Series Z Languages and general software aspects for telecommunication systems
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