ITU-T U 203-1993 Technical Requirements to be Met When Providing Real-Time Bothway Communications between Terminals of the International Telex Service and Data Terminal Equipments ing .pdf
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1、1TU-T RECMN*U*203 73 4862593 0590074 650 U INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU TELEGRAPH SWITCHING INTERNATIONAL TELEX SERVICE U.203 (03/93) TECHNICAL REQUIREMENTS TO BE MET COMMUNICATIONS BETWEEN TERMINALS OF THE INTERNATIONAL TELEX SERVICE AN
2、D DATA TERMINAL EQUIPMENTS ON A PSPDN OR VIA THE PSTN WHEN PROVIDING REAL-TIME BOTHWAY ITU-T Recommendation U.203 (Previously “CCITT Recommendation”) ITU-T RECMN*U-203 93 4862593 0590075 577 m FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International
3、 Telecom- munication Union. 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
4、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.203 was prepared by 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 re
5、form process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRE3 have been replaced b
6、y 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, CCIR or IFRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation w
7、ill contain the proper terminology 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 IT 1994 All rights reserved. No part of this publication may
8、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. CONTENTS Introduction 1.1 Scope 1.2 1.3 Functions of the TPIWF . 1.4 Methods of interworking and addressable terminals 2.1 Considering .
9、Access from the telex network to the PSPDN 3.1 One-stage selection . 3.2 Two-stage selection 3.3 Data transfer phase - Packet forwarding conditions . Access from the PSPDN to the telex network 4.1 Call establishment . 4.2 Text transfer phase 4.3 Reaction of TPIWF to data packets with M-bit set . 4.4
10、 Setting of PSPDN PAD parameters by TPIWF WRU and answerback processing 5.1 Call established from the telex network to the PSPDN 5.2 Call established from PSPDN to the telex network Clearing procedures . 6.1 Clearing initiated within the PSPDN 6.2 Clearing initiated within the telex network . Ineffe
11、ctive call attempts . 7.1 General 7.2 Ineffective calls within the telex network . 7.3 Ineffective calls within the PSPDN TPIWF PAD parameters Abnormal conditions 9.1 Telex-to-PSPDN direction 9.2 PSPDN-to-telex direction . 9.3 Flow control of the teleprinter i . 9.4 Detection of signals on the backw
12、ard path during forward transmission - Counterwriting . Outline of operational principles Special provisions for the use of PAD service signals within the international telex service Appendix I . Handling of clearing procedures by TPIWF . 1.1 General . 1.2 Clearing initiated by PSPDN 1.3 Clearing in
13、itiated from the telex network . Appendix II - Reaction by the TPIWF to ineffective call attempts within the telex network . 11.1 General II.2 Ineffective calls within the telex network . Recommendation U.203 (03/93) Page 2 2 2 3 4 4 4 5 5 7 10 10 10 12 12 12 12 12 13 14 14 14 14 14 15 15 15 15 15 1
14、8 18 18 19 19 19 19 22 22 22 1 Recommendation U.203 TECHNICAL REQUIREMENTS TO BE MET WHEN PROVIDING OF THE INTERNATIONAL TELEX SERVICE AND DATA TERMINAL EQUIPMENTS ON A PSPDN OR VIA THE PSTN REAL-TIME BOTHWAY COMMUNICATIONS BETWEEN TERMINALS (Helsinki, 1993) The CCITT, considering (a) the increasing
15、 number of data terminal equipments (DTEs) connected to public data networks; (b) the world-wide availability of the international telex service; (c) communicate with DTEs and vice-versa; the desirability of providing an appropriate mechanism whereby terminals of the international telex service can
16、(d) Recommendaiton F.69 gives the pian for telex destination codes; that Recommendation F.60 gives the operational provisions for the international telex service and (e) that Recommendation F.59 lists the essential characteristics of the international telex service; (f) international telex service a
17、nd other services; that Recommendation F.80 defines the basic requirements to be met for interworking relations between the (g) DTEs on a packet-switched public data network; that Recommendation F.83 defines the operational principies for communication between telex terminals and (h) that the U-Seri
18、es Recommendations define the technical aspects of the telex service; (i) that the classes of services, facilities and interfaces for data communication networks are defined in the relevant X-Series Recommendations, in particular, X.3, X.28, and X.29, defining the PAD function provided by a PSPDN, a
19、nd X.25 defining the interface between a packet-mode DTE and PSPDN; ti) that Recommedation X. 121 defines the international numbering pian for public data networks, unanimously deciares the view that the mechanisms to be provided to facilitate communication between telex terminals and data terminal
20、equipments (DTEs) connected to a packet-switched public data network should be in accordance with this Recommendation. Definitions The following terms used in this Recommendation have the undermentioned definitions: telex-packet interworking function (TPIWF): The Telex-Packet Interworking Function (
21、TPIWF) is a functional unit which implements the requirement to allow bothway communication between telex terminals and packet-mode and character-mode data terminal equipments directly connected to a packet-switched public data network (PSPDN) or any identified DTE accessing the PSPDN in accordance
22、with Recommendation X.28 or X.32. The method of implementation of any of the TPIW functions in any physical unit is a national matter. The functions of the TPIWF do not apply to interworking between telex and Telematic terminais, being the subject of other Recommendations. Recommendation U.203 (03/9
23、3) 1 ITU-T RECMN*U-203 93 m 4862573 0590078 2Tb W TPIWF answerback In the case of two-stage selection from the telex subscriber, the answerback which is returned in the first stage of selection and which uniquely identifies the destination TPIWF to the telex network. registered DTE: In the case of o
24、ne-stage selection, a DTE which has registered with the TPIWF for the initiation and reception of telex calls and which is assigned a telex number that is part of the telex national numbering plan for this purpose. DTE answerback: In the case of one-stage selection, the answerback that is always ret
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