1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Q.921 Amendment 1 (06/2000) SERIES Q: SWITCHING AND SIGNALLING Digital subscriber Signalling System No. 1 - Data link layer ISDN user-network interface - Data link layer specification Amendment 1 ITU-T Recomm
2、endation Q.921 - Amendment 1 (Formerly CCITT Recommendation) ITU-T Q-SERIES RECOMMENDATIONS SWITCHING AND SIGNALLING SIGNALLING IN THE INTERNATIONAL MANUAL SERVICE FUNCTIONS AND INFORMATION FLOWS FOR SERVICES IN THE ISDN SPECIFICATIONS OF SIGNALLING SYSTEMS No. 4 AND No. 5 SPECIFICATIONS OF SIGNALLI
3、NG SYSTEM No. 6 SPECIFICATIONS OF SIGNALLING SYSTEM R1 SPECIFICATIONS OF SIGNALLING SYSTEM R2 DIGITAL EXCHANGES INTERWORIUNG OF SIGNALLING SYSTEMS SPECIFICATIONS OF SIGNALLING SYSTEM No. 7 Q3 INTERFACE DIGITAL SUBSCRIBER SIGNALLING SYSTEM No. 1 INTERNATIONAL AUTOMATIC AND SEMI-AUTOMATIC WORKING CLAU
4、SES APPLICABLE TO ITU-T STANDARD SYSTEMS General Q.lLQ.3 Q.4-Q.59 Q.60.99 Q. 100.119 Q. 120.249 Q.250.309 Q.310.399 Q.400.499 Q.500.599 Q.600.699 Q.700.799 Q.800.849 Q.850.999 0.850.919 Data link layer Q.92-Q.929 Network layer User-network management Stage 3 description for supplementary services us
5、ing DSS1 PUBLIC LAND MOBILE NETWORK INTERWORIUNG WITH SATELLITE MOBILE SYSTEMS INTELLIGENT NETWORK BROADBAND ISDN SIGNALLING REQUIREMENTS AND PROTOCOLS FOR IMT-2000 Q.930.939 Q.940.949 Q.950.999 Q. 1000. 1099 Q. 1 100.1199 Q. 1200.1699 Q.1700.1799 Q.2000.2999 For further details, please re$er to the
6、 list of ITD-T Recommendations. ITU-T Recommendation 4.921 ISDN USER-NETWORL INTERFACE - DATA LINK LAYER SPECIFICATION AMENDMENT 1 Summary This Recommendation specifies the Link Access Procedures on the D-channel (LAPD) of an ISDN customer access. Implementations of this Recommendation are in use in
7、 existing networks. This Recommendation has been amended in order to add a new Annex J and a new Appendix V to describe in general terms the link access procedure for use in a symmetrical application between two Private Integrated Network Exchanges (PINXs) at the Q reference point. Source Amendment
8、1 to ITU-T Recommendation 4.921 was prepared by ITU-T Study Group 11 (1 997-2000) and approved under the WTSC Resolution 1 procedure on 15 June 2000. ITU-T Q.92UAmd.l (06/2000) 1 FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecom
9、munications. The ITU Telecommunication Standardization Sector (U-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 worldwide basis. The World Telecommuni
10、cation Standardization Conference (WTSC), 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 U-T Recommendations is covered by the procedure laid down in WTSC Resolution 1. In some areas of
11、 information technology which fall within U-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating
12、agency. 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. U takes no position concerning the evidence, validity or applicability of claimed Intellectual Property
13、 Rights, whether asserted by U members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, U had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors a
14、re cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. o mu 2001 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying
15、and microfilm, without permission in writing fiom ITU. 11 ITU-T Q.92UAmd.l (06/2000) CONTENTS Page J Annex J . Inter-exchange signalling data link layer protocol in Private Integrated Services Networks (PISNs) . Applicability and additions to frame structure, elements of procedures. formats of field
16、s. elements for layer-to-layer communication. peer-to-peer procedures to accommodate PISN inter-exchange requirements . Frame structure for peer-to-peer communication . . 1 J.2 J . 3 J.4 J.l.l J.1.2 J.1.3 J . 1.4 J.1.5 J.1.6 J.1.7 J.1.8 J.1.9 J.1.10 General . Flag sequence . Address field Control fi
17、eld . Information field Transparency Frame Check Sequence (FCS) field Format convention . Invalid frames Frame ab0 rt Elements of procedures and formats of fields for data link layer peer-to-peer communication J.2.1 General . J.2.2 Address field format J.2.3 Address field variables J.2.4 Control fie
18、ld format . J.2.5 Control field parameters and associated state variables J.2.6 Frame types Elements for layer-to-layer communication J.3.1 General . J.3.2 Primitive procedures Definition of the peer-to-peer procedures of the data link layer . J.4.1 J.4.2 J.4.3 J.4.4 J.4.5 J.4.6 J.4.7 J.4.8 J.4.9 J.
19、4.1 O Procedures for the use of the P/F bit Procedures for unacknowledged information transfer . Terminal Endpoint Identifier (TEI) management procedures Initialization of data link layer parameters Procedures for establishment and release of multiple frame operation . Procedures for information tra
20、nsfer in multiple frame operation Re-establishment of multiple frame operation Exception conditions reporting and recovery List of system parameters Data link layer monitor function ITU-T Q.92UAmd.l (06/2000) 1 2 2 2 2 2 2 2 2 3 3 3 3 4 4 5 5 5 5 5 6 6 6 7 7 8 8 . 111 Page Appendix V - Inter-exchang
21、e signalling data link layer protocol in PISNs - Occurrence of the MDL-ERROR.indication primitive in the data link layer protocol for the support of Inter-exchange signalling in PISNs . 9 V. 1 Introduction . 9 V.2 Layout of Table V.l 9 V.3 Preferred management actions 10 iv ITU-T Q.92UAmd.l (06/2000
22、) ITU-T Recommendation 4.921 ISDN USER-NETWORK INTERFACE - DATA LINK LAYER SPECIFICATION AMENDMENT 1 1) Clause 1 Add a new paragraph to the scope as follows: Annex J of this Recommendation describes in general terms the link access procedure for use in a symmetrical application between two Private I
23、ntegrated Network Exchanges (PINXs) at the Q reference point (see ISO/IEC 11579-1 8). 2) Clause 1.2 - References Add a new reference 8 as follows: 81 ISO/IEC 1 1579- 1 : 1994, Information technology - Telecommunications and information exchange between systems - Private integrated services network -
24、 Part 1: Reference configuration for PISN Exchanges (Pnvx). 3) New Annex J Add the following new Annex J: ANNEX J Inter-exchange signalling data link layer protocol in Private Integrated Services Networks (PISNs) - Applicability and additions to frame structure, elements of procedures, formats of fi
25、elds, elements for layer-to-layer communication, peer-to-peer procedures to accommodate PISN inter-exchange requirements This annex applies to the procedures for LAPD defined in clauses 1 through 5. This annex also applies to the SET MODE (SM) command, the Selective Reject (SREJ) response, and the p
26、rocedures used to support multi-selective reject option in LAPD, defined in E.l through ES - “Provision of Multi-Selective Reject Option“. The optional procedures in E. 1 through ES are referred to hereafter as the SM/SREJ option. The criteria pertaining to the use of the SM/SREJ option is specified
27、 in E.l. Clause E.l applies to this annex with the following modifications: 1) 2) Clause E. 1, as modified above, is reproduced below: Annex E defines the SET MODE (SM) command, the Selective Reject (SREJ) response, and the procedures used to support multi-selective reject option in LAPD. The multi-
28、selective reject option of LAPD reduces the sensitivity of the throughput of the Data-link layer to degradations in the Bit Error Ratio of the underlying transmission media. The procedures defined in Annex E are recommended for use on applications where there is a significant probability of having m
29、ore than one outstanding unacknowledged I-fi-ame. In the absence of such probability, the procedures of the main body of ITU-T 4.921 shall apply as amended by this annex. The use of Annex E requires bilateral agreement between peer PINX users. This bilateral agreement is applicable on a link-by-link
30、 basis. ITU-T Q.92UAmd.l (06/2000) 1 The procedures defined in Annex E are optional, and their use requires bilateral agreement between peer PINX users. These bilateral agreements are on a link-by-link basis. In the context of this annex, in the absence of provision of the procedures defined in Anne
31、x E, the procedures of the remainder of this Annex J to 4.921 shall apply. 5.1 Frame structure for peer-to-peer communication 5.1.1 General Clause 2.1 shall apply. 5.1.2 Flag sequence Clause 2.2 shall apply. 5.1.3 Address field The address field shall consist of two octets as illustrated in Figure U
32、Q.921. The format of the address field is defined in J.2.2. Networks conforming to this specification do not support the LAPB data link connection within the D-channel. 5.1.4 Control field Clause 2.4 shall apply. 5.1.5 Information field Clause 2.5 shall apply. 5.1.6 Transparency Clause 2.6 shall app
33、ly. 5.1.7 Frame Check Sequence (FCS) field Clause 2.7 shall apply with the changes as given above. 5.1.8 Format convention Clause 2.8 and its clauses shall apply. 5.1.9 Invalid frames Clause 2.9 shall apply. 5.1.10 Frame abort Clause 2.1 O shall apply. 5.2 Elements of procedures and formats of field
34、s for data link layer peer-to-peer communication 5.2.1 General Clause 3.1 shall apply. 5.2.2 Address field format Clause 3.2 shall apply. 2 ITU-T Q.92UAmd.l (06/2000) 5.2.3 Address field variables 5.2.3.1 Clause 3.3.1 shall apply. Address field Extension Bit (EA) master side to slave side 5.2.3.2 Co
35、mmand Response field bit (CR) 1 The C/R bit identifies a frame as either a comman, or response. In the case of the interconnection of two PINXs, the setting of the C/R bit for a particular data link depends on the assignment of “master“ and “slave“ sides of the inter-PINX signalling channel. The cod
36、ing of the C/R bit is shown in Table J.l below. Response Table J.UQ.921- C/R field bit usage master side to slave side slave side to master side O 1 I Command/Response I Direction I value I I Command I I slave side to master side I O I 5.2.3.3 Clause 3.3.3 shall apply with the exception that the use
37、 of any SAPI value other than O (e.g. 16 for X.25 packet mode) is beyond the scope of this annex. 5.2.3.4 Terminal Endpoint Identifier FEI) A TE1 is associated with a specific point-to-point data link between two PINXs. The TE1 value used by equipment conforming to this annex shall be the value ZERO
38、. The use of TE1 values other than O are beyond the scope of this annex. PINXs conforming to this annex shall assign the value TEI=O independently at each end of a particular inter-PINX signalling channel. 5.2.4 Control field format Clause 3.4 and its clauses shall apply. 5.2.5 Clause 3.5 and its cl
39、auses shall apply if the SM/SREJ option is not implemented, and E.3.5 and its clauses shall apply if the SM/SREJ option is implemented. 5.2.6 Frame types 5.2.6.1 Commands and responses Clause 3.6.1 shall apply with the changes as given above if the SM/SREJ option is not implemented, and E.3.6.1 shal
40、l apply with the changes given above if the SM/SREJ option is implemented. 5.2.6.2 Information (I) command Clause 3.6.2 shall apply. 5.2.6.3 Clause 3.6.3 shall apply if the SM/SREJ option is not implemented, and E.3.6.3 shall apply if the SM/SREJ option is implemented. Service Access Point Identifie
41、r (SAPI) Control field parameters and associated state variables Set Asynchronous Balanced Mode Extended (SABME) command ITU-T Q.92UAmd.l (06/2000) 3 5.2.6.4 Disconnect (DISC) command Clause 3.6.4 shall apply. 5.2.6.5 Unnumbered Information (UI) command Clause 3.6.5 shall apply. 5.2.6.6 Receive Read
42、y (RR) command/response Clause 3.6.6 shall apply. 5.2.6.7 Reject (REJ) command/response Clause 3.6.7 shall apply with the changes as given above if the SWSREJ option is not implemented, and E.3.6.7 shall apply with the changes as given above if the SM/SREJ option is implemented. 5.2.6.8 Clause 3.6.8
43、 shall apply. Receive Not Ready (RNR) command/response 5.2.6.9 Unnumbered Acknowledgement (UA) response Clause 3.6.9 shall apply if the SWSREJ option is not implemented, and E.3.6.9 shall apply if the SM/SREJ option is implemented. 5.2.6.10 Disconnected Mode (DM) response Clause 3.6.10 shall apply.
44、5.2.6.11 Frame Reject (FRMR) response Clause 3.6.1 1 shall apply if the SWSREJ option is not implemented, and E.3.6.11 shall apply if the SM/SREJ option is implemented. 5.2.6.12 Exchange Identification WID) command/response Clause 3.6.12 shall apply. 5.3 Elements for layer-to-layer communication 5.3
45、.1 General Clause 4.1 shall apply with the changes as given above and the following exceptions: a) the following generic primitive types are not part of this annex: MPH-ACTIVATE MPH-DEACTIVATE MPH-INFORMATION the following primitives are not part of this annex due to the fact that the layer 2 user d
46、oes not implement the functionality which is making use of the layer 2 services associated with these primitives: DL-UNIT DATA.request unacknowledged information transfer invoked by layer 3; MDL-UNIT DATA.request unacknowledged information transfer invoked by layer management. NOTE - Layer 3 and lay
47、er management, if receiving a DL-UNIT DATAhdication or a MDL-UNIT DATAhdication primitive, will discard its contents and not take any further action. not applicable to the Data Link Layer; not applicable to the Data Link Layer; not applicable to the Data Link Layer; b) 4 ITU-T Q.92UAmd.l (06/2000) 5
48、.3.2 Primitive procedures 5.3.2.1 General Clause 4.2.1 shall apply. 5.3.2.2 Clause 4.2.2 shall apply with the exception that the Data Link Connection Identifier (DLCI) state “information transfer“ defined in support of broadcast data link procedures is not part of this annex. Figure WQ.921 shall app
49、ly, with the exception of the state transitions as a result of the receipt of the DL-UNIT DATA.request primitive. Layer 3 - Data link layer interactions 5.3.2.3 Subclause 4.2.3 items d) and e) shall apply. The mechanism to detect loss of layer 1 capability is implementation dependent. Data link layer - physical layer interactions 5.4 Clause 5 shall apply with the changes as given above if the SM/SREJ option is not implemented, and ES shall apply with the changes as given above if the SM/SREJ option is implemented. Definition of the peer-to-peer procedures of the data link
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