1、 STDmITU-T RECMN X.2q-ENGL 3997 = 4862593 ObY5517 304 = INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU X.29 (1 2/97) SERIES X: DATA NETWORKS AND OPEN SYSTEM COMMUNICATION Public data networks - Interfaces Procedures for the exchange of control information
2、 and user data between a Packet AssemblylDisassembly (PAD) facility and a packet mode DTE or another PAD ITU-T Recommendation X.29 (Previously CCITT Recommendation) ITU-T X-SERIES RECOMMENDATIONS DATA NETWORKS AND OPEN SYSTEM COMMUNICATION Transmission, signalling and switching Network aspects Maint
3、enance Administrative arrangements OPEN SYSTEM INTERCONNECTION Model and notation Service definitions Connection-mode protocol specifications Connectionless-mode protocol specifications PICS proformas Protocol Identification Security Protocols Layer Managed Objects Conformance testing General Satell
4、ite data transmission systems MESSAGE HANDLING SYSTEMS DIRECTORY OS1 NETWORKING AND SYSTEM ASPECTS INTERWORKING BETWEEN NETWORKS Networking Efficiency Naming, Addressing and Registration Abstract Syntax Notation One (ASN. 1) Systems Management framework and architecture Management Communication Serv
5、ice and Protocol Structure of Management Information Management functions OS1 MANAGEMENT SECURITY , OS1 APPLICATIONS Commitment, Concurrency and Recovery Transaction processing Remote operations OPEN DISTRIBUTED PROCESSING 11 PUBLIC DATA NETWORKS X.1-X.199 Services and facilities X. 1 -X. 1 9 - -. .
6、 - - - . . . - -. . . terfaces X.20-X.49 X.50-X.89 X.90-X. 149 X.150-X.179 X.180-X.199 X.200-X.299 X.200-X.209 X.210-X.219 X.220-X.229 X.230-X.239 X.240-X.259 X.260-X.269 X.270-X.279 X.280-X.289 X.290-X.299 X.300-X.399 X.300-X.349 X.350-X.399 X.400-X.499 X.500-X.599 X.600-X.699 X.600-X.629 X.630-X.6
7、49 X.650-X.679 X.680-X.699 X.700-X.799 X.700-X.709 X.7 10-X.719 X.720-X.729 X.730-X.799 X.800-X. 849 X.850-X.899 X. 850-X.859 X.860-X.879 X.880-X.899 X.900-X.999 1 For further details, please refer to ITU-T List of Recommendations. STD-ITU-T RECMN X.29-ENGL 3997 = 4862591 Ob45539 187 ITU-T RECOMMEND
8、ATION X.29 PROCEDURES FOR THE EXCHANGE OF CONTROL INFORMATION AND USER DATA BETWEEN A PACKET ASSEMBLYOIISASSEMBLY (PAD) FACILITY AND A PACKET MODE DTE OR ANOTHER PAD Summary This Recommendation provides procedures to facilitate international interworking between PADS or between a PAD and a packet mo
9、de DTE. Source ITU-T Recommendation X.29 was revised by ITU-T Study Group 7 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 12th of December 1997. Recommendation X.29 (12197) 1 FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency
10、 in the field of telecommuni- cations. The IT Telecommunication Standardization Sector (IW-T) is a permanent organ of the ITU. The IT-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a world
11、wide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by
12、 the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within ITU-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 indicat
13、e both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position conc
14、erning the evidence, validity or applicability of claimed Intellectuai Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected
15、by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. O ITU 1998 All rights reserved. No part of this publication may be reproduce
16、d or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. ii Recommendation X.29 (12/97) _ STDmITU-T RECMN X-27-ENGL 1997 4862573 Ob45523 835 CONTENTS 1 Procedures for the exchange of PAD control information
17、 and user data . 1.3 Call user data 1.4 User sequences . 1.5 PAD messages 2 User data transfer . 3 Procedures for the use of PAD messages . 3.1 Procedures for reading, setting, and reading and setting of PAD parameters 3.2 3.3 Interrupt and discard procedures 3.4 Procedure for resets 3.5 Error handl
18、ing procedures by the PAD 3.6 Procedures for inviting the PAD to reselect the called DTE 3.7 Procedures for support of MAP 4 Formats . 4.1 Introduction 4.2 Call user data format (see Figure 1) 4.3 User sequence format . 4.4 Control message format Annex A - Characteristics of virtual calls and Recomm
19、endation X.25 as related to the PAD representation of a start-stop mode DTE to a packet mode DTE . A.l General interface characteristics . A.2 Interface procedures for virtual call control . A.3 Interface procedures for data transfer . A.4 Virtual call Characteristics Procedures for inviting the PAD
20、 to clear Page 2 2 2 3 3 3 3 3 4 5 5 5 6 7 7 7 7 8 14 14 14 14 15 . Recommendation X.29 (12197) 111 STD.ITU-T RECMN X.27-ENGL 1997 w 9862571 Obi15522 771 m Recommendation X.29 PROCEDURES FOR THE EXCHANGE OF CONTROL INFORMATION AND USER DATA BETWEEN A PACKET ASSEMBLY/DISASSEMBLY (PAD) FACILITY AND A
21、PACKET MODE DTE OR ANOTHER PAD (Provisional, Geneva, 1977; amended, Geneva, 1980, Malaga-Torremolinos, 1984, Melbourne, 1988, Helsinki, 1993; revised in 1997) Preface The establishment in various countries of public data networks providing packet-switched data transmission services creates a need to
22、 produce standards to facilitate international interworking. The IT-T, considering that Recommendations X.l and X.2 define the user classes of service and facilities in a public data network, a) and Recommendation X.96 defines call progress signals; b) that Recommendation X.3 defines the PAD in a pu
23、blic data network; c) that Recommendation X.8 defines the Multi-Aspect PAD (MAP) framework and service definition; 4 public data network; e packet mode in public data networks; that Recommendation X.28 defines the DTEDCE interface for a start-stop mode DTE accessing the PAD in a that Recommendation
24、X.25 defines the interface between the DTE and the DCE for DTEs operating in the f) switched transmission service; the need to allow interworking between a packet mode DTE and a non-packet mode DTE in the packet- g) the urgent need to allow interworking between a start-stop mode DTE in a public swit
25、ched telephone network, public switched data network or a leased line and a packet mode DTE using the virtual cai1 facility of the packet- switched transmission service; h) the need to allow interworking between PADs; i packet mode DTEs may wish to control specific functions of the PAD, that the pac
26、ket mode DTE shall not be obliged to use the control procedures for PAD functions, but that some unanimously recommends that 1 and the packet mode DTE; the Recommendation X.29 procedures shall apply to the Recommendation X.25 interface between the DCE 2 3 data; the Recommendation X.29 procedures may
27、 be applied for interworking between PADs; the procedures be as specified in clause 1 Procedures for the exchange of PAD control information and user 4 the manner in which user data is transferred be as specified in clause 2 User data transfer; Recommendation X.29 (12/97) 1 5 of PAD messages; the pr
28、ocedures for the control of the PAD via PAD messages be as specified in clause 3 Procedures for the use 6 NOTE 1 - For ease of understanding, this Recommendation refers to specific packet types and procedures of Recommendation X.25. When PAD-to-PAD interworking is considered within a national networ
29、k, these packet types or procedures may have a different form from those used in Recommendation X.25 but will have the same operational meaning. NOTE 2 - The following items are for further study: the formats of the data fields which are transferable on a virtual call be as specified in clause 4 For
30、mats. - the use of the permanent virtual circuit service; - interworking between DEs having interfaces to different data transmission services; - operation of non-packet mode DTEs in other than start-stop mode. 1 Procedures for the exchange of PAD control information and user data 1.1 is performed b
31、y using user data fields defined in Recommendation X.25. The exchange of control information and user data between a PAD and a packet mode DTE or between PADs 1.2 Annex A describes some of the characteristics of virtual calls as defined in Recommendation X.25, as related to the PAD representation of
32、 a start-stop mode DTE to a packet mode DTE. The characteristics described in Annex A also apply for interworking between PADs. 1.3 Call user data The call user data field of incoming call or call request packets to or from the packet mode DTE or the PAD is comprised of two fields: a) the protocol i
33、dentifier field; and b) the call data field. The protocol identifier field is used for protocol identification purposes and the call data field contains user data. An incoming call packet received by the PAD, containing no call user data field, will be accepted by the PAD. If a call data field is pr
34、esent, the PAD will send it, unchanged, to the start-stop mode DTE, using the call data block of the incoming call PAD service signal (see 3.5.22iX.28). 1.4 User sequences 1.4.1 User sequences are used to exchange user data between the PAD and the packet mode DTE or a PAD. 1.4.2 directions on a virt
35、ual call. (See Recommendation X.25.) User sequences are conveyed in the user data fields of complete packet sequences with Q = O, and in both 1.4.3 There will be only one user sequence in a complete packet sequence. 1.4.4 The PAD will transmit all data packets with the D bit set to O. On reception o
36、f a data packet with the D bit set to 1, the PAD will transmit the corresponding acknowledgement as soon as possible. If the PAD does not support the D bit procedure, the PAD may reset the virtual call. As no error correction procedure is in place from the PAD to the start-stop mode DTE, no guarante
37、e of delivery can be implied from the acknowledgement. 2 Recommendation X.29 (12/97) STDeITU-T RECMN X-29-ENGL 1997 = YB62591 0645524 544 1.5 PAD messages 1.5.1 PAD messages are used to exchange control information between the PAD and the packet mode DE (or remote PAD). A PAD message consists of a c
38、ontrol identifier field and a message code field possibly followed by a parameter field (see 4.4). 1.5.2 directions on a virtual call. (See Recommendation X.25.) PAD messages are conveyed in the user data fields of complete packet sequences with Q= 1 and in both 1.5.3 1.5.4 1.5.5 appearance is taken
39、 into account. 1.5.6 On reception of a datu packet with both the Q bit and the D bit set to 1, the PAD will transmit the corresponding acknowledgement as soon as possible. There will be only one PAD message in a complete packet sequence. The PAD will take into consideration a PAD message only when i
40、t has been completely received. In the case where a parameter reference (see clause 3) appears more than once in a PAD message, only the last The PAD will transmit all data packets with the D bit set to O. If the PAD does not support the D bit procedure, the PAD may reset the virtual call. 2 User da
41、ta transfer 2.1 under any of the other data forwarding conditions provided by the PAD (see 4.4K.28). 2.2 Data packets will be forwarded by the PAD when a set, read, or set and read PAD message is received, or The occurrence of a data forwarding condition will not cause the PAD to transmit empty data
42、 packets. 3 Procedures for the use of PAD messages 3.1 3.1.1 und read PAD message. Procedures for reading, setting, and reading and setting of PAD parameters The current values of PAD parameters may be changed and read by transmitting to the PAD a set, read, or set 3.1.2 When the PAD receives a set,
43、 read or set und read PAD message, any data previously received will be delivered to the start-stop mode DTE before taking action on the PAD message. The PAD will also consider the arrival of such a PAD message as a data forwarding condition. 3.1.3 The PAD will respond to a valid read or set and rea
44、d PAD message by transmitting a parameter indication PAD message. This PAD message will have a parameter field containing a list of parameter references and current values (after any necessary modification) of the PAD parameters to which the received PAD message referred. 3.1.4 received. The PAD wil
45、l not return a parameter indication PAD message in response to a valid set PAD message 3.1.5 Table 1 specifies the PADS response of the PAD to set, set and read, and read PAD messages. 3.1.6 If the function of a character is duplicated by the selection of parameter values by use of the set or set un
46、d read PAD message, the PAD will consider these parameter changes as valid, and will respond as described in this Recommendation. After these changes are invoked, the PAD will follow the procedure described in Recommendation 3.3.2K.28. 3.2 Procedures for inviting the PAD to clear 3.2.1 The invitatio
47、n to clear PAD message is used to request that the PAD clears the virtual call, after transmission of all data previously transmitted to the start-stop mode DE. NOTE - The clear request packet, which is transmitted by the PAD after delivery of the last character to the start-stop mode DE, will have
48、a clearing cause field set to DTE clearing. Recommendation X.29 (12/97) 3 STDmITU-T RECMN X.29-ENGL 3997 m 4862593 0645525 480 m PAD message received by the PAD Action upon PAD parameters Parameter field Table 1K.29 -PAD messages transmitted by the PAD in response to set, set and read, and read PAD
49、messages Corresponding parameter indication PAD message transmitted to the packet mode DTE List of selected parameters with the desired values Set Set the selected parameters to the given values: a) if no error is encountered a) None b) if the PAD fails to modify the b) List of these invalid values of some parameters parameters (Note) Set and read Reset all implemented Recommendation X.3 parameters to their initial values corresponding to the initial profile Read List all implemented Recommendation X.3 parameters, and their initial value
