1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU TELEGRAPH SWITCHING TELEX STORE AND FORWARD U .80 (03/93) INTERNATIONAL TELEX STORE AND FORWARD ACCESS FROM A TELEX SUBSCRIBER ITU-T Recommendation U.80 (Previously “CCITT Recommendation”) ITU-T RECMN*U*BO 93
2、 = 48b259L 0594Lb9 833 R FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardi
3、zing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. ITU-T Recommendation U.80 was revised b
4、y the ITU-T Study Group IX (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In its place, the ITU Telecommunication Standardiza
5、tion Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IERB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendation, no change has been made in the text to references containing the acronyms “CCITT
6、, CCIR or IFRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure. 2 telecommunication administration and a recognized operating agency. In this Recommendation, the expr
7、ession “Administration” is used for conciseness to indicate both a O ITU 1994 Ali rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. ITU-T
8、RECNN*U=BO 93 48b2571 0594170 555 CONTENTS 1 Scope 2 Outline of service features 2.2 Service principies 3 Outline of facilities . 3.2 Message input access 3.3 Status enquiry access 4 Access procedures 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.1 1 4.12 General Telex access Service request Calling te
9、lex address . Commence input signal Address input Called address validation Message input . End of message (EOM) signal End of transaction (EOT) Message reference information . Input transaction accepted for delivery signal (ITD) 5 Status enquiry . 5.1 Status enquiry request . 5.2 The status report
10、. Abnormal conditions during message input . 6 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 Telex subscriber clearing during text input without EOT Telex subscriber stopping transmission for a certain time without transmitting the EOT signal, or transmitting a partial or invalid EOT signal . Telex subsc
11、riber sending WRU to the SFU during text input Telex subscriber sending text after the EOT signal Telex subscriber clearing after EOT, but before ITD . Telex subscriber sending national variants of ITA No . 2 Alphabet (?F, ?G, bI) . Telex subscriber sending J . Bell combination (h) . SFU storage cap
12、acity overflow during telex message input . Maximum input duration exceeded Repeated characters during message input . Page 1 1 1 2 2 3 3 3 6 7 7 7 8 8 11 11 12 12 12 13 13 13 13 13 14 14 14 15 15 15 15 15 15 Recommendation U.80 (03/93) 1 ITU-T RECflN*U-BO 73 M 4862573 0594373 q7L I Recommendation U
13、.80 INTERNATIONAL TELEX STORE AND FORWARD ACCESS FROM A TELEX) SUBSCRIBER (Malaga-Torremolinos, 1984; amended at Melbourne, 1988 and ar Helsinki, 1993) The CCITT, considering (a) (b) (c) desirable, that telex store-and-forward units exist, and are being introduced increasingly into national networks
14、; that access procedures and protocols differ significantly between different units; that to facilitate international access to store-and-forward units, a standard access procedure would be unanimously declares the view that the telex access procedure described in this Recommendation should be adopt
15、ed for all future store-and-forward units providing incoming international telex access. 1 Scope 1.1 This Recommendation describes a procedure for a telex subscriber to gain access to a store-and-forward unit in a foreign country by using an international telex switched connection. The procedure use
16、s two stage selection. 1.2 This Recommendation is one of a series which defines telex store-and-forward services. The other Recommendations are: Recommendation F.72 The international telex service - General principles and operational aspects of a store-and-forward faciliq. Recommendation U.8 1 Inter
17、national telex store-and-fomard - Delivery to a telex subscriber. - - 2 Outline of service features 2.1 The full range of service features is described in more detail in Recommendation F.72. 2.2 Service principles 2.2.1 The procedure defined in this Recommendation is a two stage selection procedure
18、whereby a calling telex subscriber gains access to a foreign store-and-forward unit (SFU) in the first stage of selection and inputs the called address(es) and message in the second stage of selection, after the return of a call connected signal. The option of a store and retrieval facility is for f
19、urther study. Throughout this Recommendation, the term “telex” should be interpreted as referring exclusively to “the international telex service”, as described in Recommendations F.59 and F.60. Recommendation U.80 (03/93) 1 ITU-T RECMN*U.BO 93 W 48b259L 0594372 328 2.2.2 International access to the
20、 SFU should be offered on the basis of bilateral agreement between Administrations, and barring facilities should be provided to prevent unauthorized use. The method of barring shall be the responsibility of the Administration of the SF service and is beyond the scope of this Recommendation. It may
21、also be necessary for Administrations to make provision to selectively bar access to international telex SFU facilities in other countries. 2.2.3 Message input from both manual and automatic emitting devices should be accommodated. It is also possible that messages may be received from another SFU,
22、and this type of input should also be accommodated by bilateral agreement. 2.2.4 be able to handle direct input of the address from the subscriber, with or without prompt. For calling subscribers with answerbacks that cannot be processed to obtain the calling address, the SFU shall 2.2.5 A status en
23、quiry facility should be provided internationally to provide information on message delivery in response to a request from the originator. This message status enquiry point will be accessed by a separate access code to that used for message input. When the SFU provides automatic advice of delivery a
24、nd non-delivery, or a request for positive delivery can be indicated, then the provision of status enquiry facilities is optional. 2.2.6 given address cannot be fully guaranteed. Address validation of the called telex subscriber(s) may be provided, however, delivery of the message to a 3 Outline of
25、facilities 3.1 The full range of facilities is describa in more detail in Recommendation F.72. 3.2 Message input access 3.2.1 Provision should be made for both single and multi-addressed calls. 3.2.2 Delivery Notification with service code NA for the reason of non-delivery. Messages received by the
26、SFU for delivery to destinations not served by that SFU should be given a Non- 3.2.3 The maximum acceptable number of addresses in a multi-address call shall be agreed between Administrations, but should be at least 20. If the maximum number of addresses is exceeded, the SFU shall return the service
27、 code TMA and clear the connection. 3.2.4 address message to have a relevant attention prefix preceding the message. An attention information field facility should be provided by the SFU which enables each addressee of a multi- 3.2.5 Three classes of delivery service should be provided by the SFU: a
28、) b) Normal delivery - The SF delivers the message as soon as operationally feasible after receipt. Delayed delivery - The delay can be either: i) ii) set by the Administration offering the SFU service, if the calling customer selects this option; set by the calling subscriber, such that delivery of
29、 the message is not attempted until after the expiration of the indicated delay. c) Time limited delivery set by the calling subscriber - such that delivery of the message is attempted within a specified time limit. The desired class of delivery should be selectable on a destination address basis. 3
30、.2.6 message or on a per address basis. Positive delivery notification (PDN) when provided may be requested by the calling subscriber on a per 3.2.7 Message reference number(s) should be returned to the calling subscriber. 2 Recommendation U.80 (03193) ITU-T RECMN*U.O 93 4862593 0594373 264 U 3.2.8
31、Address correction procedures are considered desirable and may be provided. 3.2.9 Provision should be made to accept follow-on message(s) with their associated address(es) which may be sent as separate block(s) immediately after the first message. Provision should also be made to acknowledge accepta
32、nce of messages, if requested by the calling terminal, at any point during a transaction. 3.2.10 The SFU shall not accept the input of a message or follow-on messages (in the message input mode) unless adequate storage is available. The minimum storage available per message text input should be agre
33、ed bilaterally between Administrations. However, it is recommended that the minimum storage available on a per message basis should be 24 O00 characters. For an interim period 12 O00 characters is acceptable. Longer messages may be accepted if storage continues to be available. 3.2.11 to indicate th
34、at the SFU has accepted the message. An Input Transaction Accepted for Delivery (ITD) service signal should be returned to the calling subscriber 3.2.12 and are for further study: The following facilities are not accommodated in the procedures, do not form part of this Recommendation a) b) message e
35、diting facilities; c) address collation facilities; d) e) f) called address format checks. use of pre-recorded address lists; requests for positive delivery advices; transparent mode in message input phase; 3.3 3.3.1 3.3.2 4 4.1 4.1.1 Status enquiry access Status information on messages should only
36、be available for return to the originator of the message. Status information may be requested on a) b) c) a specific address. ail addresses associated with a message reference number; addresses which have not yet received the message; Access procedures General Two basic access procedures should be p
37、rovided: a) Interactive operation Input from manual calling terminals, where the SFU may return prompt signals. b) Non-interactive operation - Either, input from automatic emitting devices or from subscribers terminals, where prompt signals from the SFU are not required; or - input from another SFU.
38、 the format of this answerback is for further study. NOTE - Detection of this type of access will rely on the identification of the calling SF answerback, Recommendation U.80 (03/93) 3 ITU-T RECMN*U=BO 93 m 48b2593 0594374 LTO m 4.1.2 Figure 1 shows the recommended access procedures. Message (Notes
39、1 O, 11) 4 reference info FIGURE 1AJ.80 SFU access prdocd NOTES to Figure 1 1 2 The WRU signal is transmitted 800 ms after transmission of the SFU answerback if the forward path remains idle. One additional WRU signal shall be transmitted by the SFU if: a) there was no response to the first WRU sign
40、al. b) signais were received after the first WRU which could not be identified as an answerback. This second WRU signal should be transmitted when a 300 ms idle condition has been detected from the calling terminal at least 2 seconds after the transmission of the first WRU signal. 3 Case A: Procedur
41、e when calling address can be determined from the calling terminal answerback. 4 Case B: Procedure when calling address cannot be determined from the calling terminal answerback. 5 The prompt GA and the preceding optional message reference information shall be transmitted three seconds after receipt
42、 of the calling terminal answerback. If the caller initiates input within the three seconds timeout. the message reference information and prompt will be withheld. 6 The prompt “ADD and the precedent optional message reference information shall be transmitted three seconds after receipt of the calli
43、ng terminai answerback. If the caller initiates input within the three seconds timeout, the reference information and prompt will be withheld. 4 Recommendation U.80 (03/93) ITU-T RECMN*U.BO 93 = 4862571 0594375 037 U 7 The service request CI is transmitted when the terminal is operating in a non-int
44、eractive mode (e.g. an automatic terminal or a manual terminal using a tape transmitter). 8 If the calling address is expected and is not received within 15 seconds of the original “ADD” prompt, a further prompt shall be transmitted. The procedure is shown in Figure 2. The calling address should be
45、input in the format F.69 destination code followed by the national telex number followed by at least 2 camage returns, line feed sequences when received in the non-interactive mode. 9 The prompt GA is inhibited if the service request CI has been received or if the caller has initiated input. 10 Seve
46、ral messages can be contained within the same transaction and are separated by EOM sequences, as in Figure 3. 11 The EOM signal may optionally be followed directly by an ACK request signal. The sequence will then be as shown in Figure 4. Immediately following transmission of an IMA, the SFU shall re
47、turn reference information for previous unacknowledged messages, the signal t = 1 GA t = and then be prepared to accept further follow-on messages. i2 Following receipt of the EOT signal the SFU shall operate as shown in Figure 5. a) If the EOT signal originated from a non-interactive telex terminal
48、, the SFU should wait for up to 2 seconds for a WRU signal. If a WRU signai is received, the SFU should return its answerback followed immediately by the ITD sequence. If a WRU signal is not received in the 2 second period, the SFU should return the ITD sequence. b) If the EOT signal originated from
49、 an interactive telex terminal, the SFU should return the ITD sequence as soon as possible. c) The ITD signal and associated reference information must be returned within 5 seconds of the EOT signal. If a WRU signal is received at any time during the procedure, the SFU shall return its own answerback. 13 FIGURE WU.80 Messace Y (see Note 11 Address(es) of Figure 1) Messace Y Recommendation U.80 (03/93) 5 ITU-T RECMN*U.BO 93 M 4862591 059417b T73 SFU -s-.- Address( es) -I To90 1220-461404 FIGURE 4AJ.80 I ITD FIGURE 5N.80 4.2 Telex access 4.2.1 The calling telex subscriber shoul
