ITU-T T 62 BIS-1993 Control Procedures for Teletex and G4 Facsimile Services Based on Recommendations X 215 and X 225 - Telematic Services Terminal Equipments and Protocols for Tel.pdf

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1、STDSITU-T RECMN T-bZ BIS-ENGL 1773 m 4b2591 Ob20214 5TT INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMM U N CATION STANDARDIZATION SECTOR OF ITU T.62 bis TELEMATIC SERVICES TERMINAL EQUIPMENTS AND PROTOCOLS FOR TELEMATIC SERVICES (03/93) CONTROL PROCEDURES FOR TELETEX AND G4 FACSIMILE SERVICES

2、BASED ON RECOMMENDATIONS X.215 AND X.225 ITU-T Recommendation T.62 bis (Previously “CCIlT Recommendation”) STD-ITU-T RECMN T*b2 BIS-ENGL It773 W 4Bb257L Ob20215 43b FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union.

3、The 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 Telecommunication Standardization Conference (WTSC). which meets every four years, established the topic

4、s for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. ITU-T Recommendation T.62 bis was revised by the ITU-T Study Group VI11 (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform process within the

5、International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In its place, the IT Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication S

6、ector. In order not to delay publication of this Recommendation, no change has been made in the text to references containing the acronyms “CCIT, CCIR or IFRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper term

7、inology related to the new IT structure. 2 telecommunication administration and a recognized operating agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a O ITU 1994 All rights reserved. No part of this publication may be reproduced or utilized

8、in any form or by any means, electronic or mechanical, including photocopying and microfilm. without permission in writing from the ITU. STD*ITU-T RECMN T-b2 BIS-ENGL 1773 YBb2571 Ob2021b 372 W CONTENTS Scope and field of application References Actions for performing the control procedures for Telet

9、ex and Group 4 facsimile . 3.1 General 3.2 Session connection establishment phase . 3.3 Session termination phase . 3.4 Document management 3.5 Miscellaneous . Usage of the session service . 4.1 General 4.2 Session connection establishment . 4.3 Session termination phase . 4.4 Data transfer phase .

10、Recommendations for implementing the session layer 5.1 Additional parameters . 5.2 Implementation choices Annex A . Definitions A.1 General A.2 Session layer mode of communication . A.3 Terms specific to document Annex B - State diagrams . Annex C - Types of documents C.l General C.2 Normal document

11、 . C.3 Operator document (optional) . C.4 Control document . C.5 Monitor document (optional) Annex D - Protocols for interactive applications Recommendation T.62 bis (0393) Page 1 1 1 1 1 2 2 5 7 7 8 12 13 18 18 21 23 23 23 24 24 29 29 29 29 29 29 30 I STD*ITU-T RECMN T*b2 BIS-ENGL 1773 M 98b257L Ob

12、20217 209 M INTRODUCTION This Recommendation is related to other Recommendations. In particular it is related to certain Recommendations as defined by the Reference Model for Open Systems Intercon- nection (see Recommendation X.200). This Recommendation is based on the description of the session ser

13、vice (see Recommendation X.2 15) and the session protocol (see Recommendation X.225) as shown in Figure 1. X.215 - Equivalent to T.62 x225 (1) TO817530-94/a)l FIGURE 1f.62 bis For this Recommendation, Version i of the session protocol is used. This implies several types of restrictions, for example

14、on the length of the user data fields. These restrictions are fully described for the protocol in Annex Dm.225 and they must be applied in the same way at the service, NOTES 1 2 Only the services and protocol elements relevant to Recommendation T.62 procedures are used (see Table 1). The session pro

15、tocol described in Recornmendation X.225 is based on the services provided by the transport layer as described in Recommendations X.214 and X.224. For compatibility with Teletex and Group 4 facsimile, additional rules (in accordance with Recommendation T.70, clause 5, including Annexes A and B) must

16、 be applied when using the transport service and protocol (see Recommen- dations X.214 and X.224, class O). The control procedure for Teletex and Group 4 facsimile are currently described in Recommendation T.62. Recommendation T.62 may be superseded by this Recommendation and the appropriate session

17、 layer service and protocol described in the Recommendations X.215 and X.225. When using either Recommendation T.62 bis (based on the X-Series Recommendations) or Recommendation T.62 (based on Recommendation T.70) it is intended that the externally visible protocols are equal. It is the intention th

18、at Recommendations X.215 and X.225 together with this Recommendation do have the same level of detail and accuracy as Recommendation T.62 already has. However, for the time being Recommendation T.62 will be kept and in cases of discrepancy andor incompatibility, Recommendation T.62 will take precede

19、nce over Recommen- dations X.2 15 and X.225 together with the application rules described in this Recommendation. This Recommendation covers all of Recommendation T.62 including the annexes. II Recommendation T.62 bis (03/93) Recommendation T.62 bis CONTROL PROCEDURES FOR TELETEX AND 64 FACSIMILE SE

20、RVICES BASED ON RECOMMENDATIONS X.215 AND X.225 (Melbourne, 1988; amended at Helsinki, 1993) 1 This Recommendation defines: Scope and field of application I) 2) A set of rules for using the OS1 Session Service. The additional requirements for the implementation to conform to the control procedures f

21、or Teletex and Group 4 facsimile services. The set of rules consists of: - - - The actions to be taken by the session user for performing the control procedures. The description of the use of the session service primitives and their parameters. The encoding of parameters not covered by the session l

22、ayer (for these parameters see also 5.2). These parameters are described as additional parameters for each primitive and each SPDU where appropriate. The length and value of these parameters are provided by the SS-user and no checking is made by the session layer itself. 2 References Recommendations

23、 F.161, F.200, X.215, X.225, T.563, T.503, T.521. T.6, T.35. T.60, T.61, T.62, TAW-Series, T.390 and X.200. 3 Actions for performing the control procedures for Teletex and Group 4 facsimile This clause describes the Teletex application protocol in terms of actions involving the session service primi

24、tives. 3.1 General The control procedures for Teletex and Group 4 facsimile are designed to allow data to be transferred and managed between terminals in the form of documents. The present Recommendation only provides for the transfer of documents. As a consequence, no transfer of data can take plac

25、e outside a document. - - A document is composed of one or more pages. Pages are sent sequentially and each page has to be individually acknowledged. However, several pages may be sent without waiting for the acknowledgement and the number of pages which can be sent in this manner is called the wind

26、ow-size. The transfer of a document is executed from the source to the sink (see 3.2.3 and 3.4). For the purpose of the description, in the remainder of the text, the source is also called the sender and the sink is also called the receiver. - 3.2 Session connection establishment phase 3.2.1 The cal

27、led SS-user may accept or refuse the connection by issuing the S-CONNECT response primitive. It is the responsibility of the initiator of the connection to examine the parameters sent by the remote terminal at session initiation and to determine whether the session should continue, If it is not to b

28、e continued, the session shall be ended normally. The calling SS-user initiates the connection by issuing the S-CONNECT request primitive. Recommendation T.62 bis (OW931 1 - STD-ITU-T RECMN T.b2 BIS-ENGL 1993 W Li8b2571 Ob20217 081 3.2.2 A session connection is identified by means of a) the basic se

29、ssion reference (mandatory parameter) composed of: - terminal identifier of the called terminal; - - date and time; terminal identifier of the calling terminal; b) an optional additional session reference number, to uniquely identify the session connection. 3.2.3 At session connection establishment,

30、 the data. minor synchronize and majorlactivity tokens shall be available and assigned to the initiator side. Thus at session initiation the initiator is defined as being the current source of text information and is therefore the source terminal. 3.2.4 S-TOKEN-PLEASE request. When accepting the con

31、nection the called SS-user may request the session control by issuing the primitive In continuing the session, neither terminal is permitted to use any procedure or to send any information that does not comply with the receiving capabilities indicated by the session partner in the service identifier

32、 and non-basic session and terminal capabilities parameters of the S-CONNECT primitives at session initiation and/or by the parameters of S-CAPABILITY -DATA primitives. 3.2.5 The following rules shall apply to the private use and presently not defined parameters: a) The use of these parameters in ot

33、her primitives than S-CONNECT and S-CAPABILITY-DATA must be negotiated upon in advance by S-CONNECT or S-CAPABILITY-DATA. Presence of these parameters unexpectedly in other primitives may result in procedural errors. The absence of a parameter of this kind in a response to S-CONNECT or S-CAPABILITY-

34、DATA must be interpreted as an indication that the terminal is not capable of handling any of these functions. b) 3.3 Session termination phase The session connection is terminated by means of the S-RELEASE services for normal (or error-free) termination. The S-U-ABORT/S-P-ABORT services may be used

35、 at any time by either terminal to terminate a session. whenever a condition is detected indicating that the session cannot be continued successfully. S-U-ABORT/S-P-ABORT shall only used when there is no other suitable way of ending the session. In the two-way alternate or one way communication mode

36、, only the sender of the S-CONNECT request may send the S-RELEASE request when he is the current source. NOTE - The transport connection may be reused as a local implementation choice and this may depend on an application decision which may be passed across the session service interface. 3.4 Documen

37、t management The document concept, as defined in Recommendation T.62, is mapped onto the activity concept of the session protocol. Consequently, the document number corresponds to the activity identifier. The transfer of a document is delimited by a start and an end. A document is sent by the source

38、 (sender) to the sink (receiver) and this transfer may only take place when the source owns ali the available tokens. When the sink wants to send a document it may express this requirement by issuing an S-TOKEN-PLEASE primitive. When the transfer of a document is terminated, the sender may give the

39、control to the receiver by issuing an S-CONTROL-GIVE primitive. But there is no requirement for sending text information prior to issuing an S-CONTROL-GIVE primitive. When the protocol element exchange corresponding to this primitive is executed, all the tokens are assigned to the receiver; conseque

40、ntly it becomes *e source (or sender) and the former source becomes the sink (or receiver). A document transfer may then be started from the new source to the new sink. 2 Recommendation T.62 bis (03/93) STD-ITU-T RECMN T.b2 BIS-ENGL 1991 48b257L 0b20220 AT3 = 3.4.1 Start of document The S-ACTIVITY-S

41、TART service indicates the start of a document. It also indicates the start of the first page. 3.4.2 Page boundaries 3.4.2.1 The S-SYNC-MINOR service indicates the boundary between pages. It also indicates a checkpoint for error recovery purposes and invites the sink to accept responsibility for the

42、 previously received page. In the basic services a checkpoint must be inserted at each page boundary using S-MINOR-SYNC request. Each checkpoint must be explicitly acknowledged in the right sequence, by using S-SYNC-MINOR response. Consequently the checkpoint reference number corresponds to the mino

43、r synchronization point serial number. The S-SYNC-MINOR response shall be used to indicate that the receiver accepts responsibility for that page. If the receiver does not accept the responsibility for the page he shall use the S-U-EXCEPTION-REPORT service. In this case the transmission must be inte

44、rrupted by the sender using the S-ACTIVITY-INTERRUPT or DISCARD services. The receiver may reject reception for a detected error, but he is not obliged to check the document for errors. Once a page has been positively acknowledged, any error recovery for the subsequent detection of an error is beyon

45、d the scope of these control procedures. 3.4.2.2 When a source terminal receives an S-SYNC-MINOR confirmation with the receiving ability jeopardized (RAJ) parameter set to 1 (see 4.4.6) during a document transmission, it may continue to transmit one or more pages until the window is closed. In this

46、context the following rules apply: a) if the source subsequently receives an S-SYNC-MINOR confirmation with the RAJ parameter set to O (see 4.4.6), it will be able to continue transmission; b) if the source subsequently receives an S-U-EXCEPTION-REPORT with a parameter value “SS-user receiving abili

47、ty jeopardized” (indicating “memory overflow”), the document transmission should be terminated abnormally. The source shall issue either an S-ACTIVITY-DISCARD request or an S-ACTIVITY-INTERRUPT request. 3.4.2.3 When a sink terminal sends an S-SYNC-MINOR response with the receiving ability jeopardize

48、d parameter set to 1, and subsequent memory overflow results in sending S-U-EXCEPTION-REPORT. the value of the reason code will be “SS-user receiving ability jeopardized” (indicating “unable to continue the session”). 3.4.3 End of document 3.4.3.1 The S-ACTIVITY-END service shall be used to indicate

49、 the end of a document. It also indicates the end of the final page and as such represents the final checkpoint. The S-ACTIVITY-END response gives a positive acknowledgement to the last checkpoint. In the basic services this is the last page reference number. When confirming this service, the receiver shall indicate that: a) b) c) he has not detected an error; he accepts responsibility for the received document; he is ready to receive a new S-ACTIVITY-START or S-ACTIVITY-RESUME request. To refuse the checkpoint indicated in S-ACTIVITY-END indication, the SS-user shall us