1、ITU-T RECMN*U=LOL 93 m 4862593 0588793 43b m INTERNATIONAL TELECOMMUNICATION UN ION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU TELEGRAPH SWITCHING INTEX SERVICE u.1 o1 (03/93) SIGNALLING SYSTEMS FOR THE INTEX SERVICE (TYPES E AND F SIGNALLING) ITU-T Recommendation U.l O1 (Previously “CCIl
2、T Recommendation”) ITU-T RECMN*U.LOL 93 4862573 0588792 372 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 Recommendatio
3、ns 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 topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. ITU-
4、T Recommendation U.101 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 reform process within the International Telecommunication Union (ITU), the CCIT ceased to exist as of 28 February 1993. In its place, t
5、he ITU 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 Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendation, no change has been made in the text to refer
6、ences containing the acronyms ?CCITT, 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 agen
7、cy. 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 in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permis
8、sion in writing from the ITU. ITU-T RECMN*U-LL 93 W 4862593 0588793 209 D CONTENTS Page 1 Type E signalling 1 . 2 Type F signalling 25 3 Interworking between Types E and F signalling 27 Recommendation U.101 (03/93) i I ITU-T RECMN*U.LOL 73 4862591 0588794 145 Recommendation U.101 SIGNALLING SYSTEMS
9、FOR THE INTEX SERVICE TYPES E AND F SIGNALLING) (Helsinki, 1993) The CCITT, considering (a) that new networks are being introduced based upon stored program control techniques; (b) that these networks as well as being able to carry the International Telex Service, can also carry the Intex service us
10、ing alphabets other than the International Telegraph Alphabet No. 2 and that interworking between these services is essential; (c that the equipment provided for these networks supports an enhanced range of facilities but that for speed and ease of introduction of the Intex service some Administrati
11、ons may wish not to offer these enhanced facilities at the outset; (4 that the Intex service requires the establishment of new types of signalling, and these signalling types shall permit intenvorking between Intex terminals, between telex terminals and Intex terminals, and between telex terminals a
12、nd terminals capable of operating both telex and Intex dual service terminals; (e) that Recommendation S.33 defines the alphabet and presentation characteristics for Intex; (f Service and the Intex service; that Recommendation U.2 1 O defines the network interworking requirements between the Intemat
13、ional Telex (g) Telex Service; that Recommendation S.34 describes Intex terminal requirements to effect interworking with the Intemational (h) that Recommendation S.35 defines the composition of answerbacks for the Intex service; (i) (i) Intex service and the International Telex Service; provisions
14、of this Recommendation should be applied to such services. that Recommendation F.150 defines the operational and service requirements of the Intex service; that Recommendation F.82 defines the operational and service requirements for intenvorking between the NOTE - The development in the future of s
15、ervices similar to Intex may occur. It may be possible that some of the unanimously declares the view (1) adopted on trunks between switching centres, that to support a full range of enhanced customer facilities, Type E signalling as described in clause 1, shall be (2) signalling as described in cla
16、use 2 may be adopted on trunks between switching centres, (3) that where an Administration does not wish to offer a full range of enhanced customer facilities Type F interworking between Types E and F signalling is for further study (see clause 3). 1 Type E signalling 1.1 General switching and signa
17、lling principles 1.1.1 Type E signalling is independent of the speed and code conversion method and may be used over synchronous or asynchronous channels. Decentralized signalling shall apply with the same channel being used for control signalling and information transfer. Recommendation U.101 (03/9
18、3) 1 ITU-T RECNN*U=303 93 = 4862593 0588795 081 1.1.2 signalling control of calls shall be adopted. Both terminal and transit operation shall be supported. Due to the inclusion of transit operation, link-by-link 1.1.3 Onward selection from transit and incoming terminal centres shall be arranged to .
19、overlap the reception of selection signals in order to minimize call Set-up times. Selection signals shall be transmitted by the originating centre at automatic speed in a single block that includes an end of selection signal. 1.1.4 codes shall be used for network identification purposes. The schedu
20、le of telex destination codes detailed in Recommendation F.69 shall apply. The same numerical 1.1.5 Alternative routing shall be permitted but shall be restricted in order to prevent repeated altemative routing causing traffic to circulate. Alternative routing shall therefore be allowed only once in
21、 the originating network, once during intemational routing between the originating and terminal networks, and once in the terminal network. 1.1.6 Both-way operation shall be assumed. In order to minimize head-on collisions inverse order testing of circuits shall be used. Also allowed is a close appr
22、oximation to inverse order testing whereby the route is tested in small groups in fixed order always starting the search from the same position. 1.1.7 accounting information by other than the originating network is for further study. Normally the originating network shall be responsible for recordin
23、g accounting information. The recording of 1.1.8 The Grade of Service for the provision of circuits shall not be worse than one lost call in 500. 1.1.9 calls in the busy hour, and only when congestion has been positively identified. Operation of switching equipment shall be such that congestion shal
24、l not be signalled on more than 0.2% of 1.2 Specific signalling characteristics Notes applicable to 1.2 NOTES 1 X denotes the international centre that originates the call under consideration on the international link concerned. Y denotes the international centre that receives the call under conside
25、ration on the intemational link. Centre X and centre Y shall provide any necessay signalling conversion (including speedcode conversion) to the type of signalling employed on the preceding and succeeding links if these do not use Type E signalling. 2 3 Timings shown are within the centre concerned w
26、ith no allowance being made for propagation and other delays. The times for permanent start polarity (A) and stop polarity (Z) are generally indicated in the following signal descriptions as integral multiples of the duration of a character. 4 The control signalling code (CSC) used in this signallin
27、g system is described in Table 8. 1.2.1 signalling is detailed in Table 1. The signalling system for higher baud rate services between two anisochronous networks using Type E 1.2.2 On incoming calls, if the duration of the calling signal exceeds two character periods (or four character periods in ex
28、ceptional cases where extension of call signais has been requested by centre Y) start polarity shall be maintained on the backward signalling path from centre Y to centre X. This will cause the connection to be released by centre X. 1.2.3 The first forward path signal following the calling signal (c
29、lass-of-traffic signal) is distinctive from the first backward path signal to provide positive detection of head-on collisions on bothway circuits. A head-on collision is indicated by the reception of a first class-of-raffic character instead of the reception confirmation or reception congestion sig
30、nal. When a head-on collision is detected, the switching centres at each end of the circuit shall make another attempt to select a free circuit, either on the same group of circuits or on an alternative route if one exists and alternative routing is permitted. If no free circuit is found, or if a fu
31、rther head-on collision is detected, the call shall be cleared. At transit centres call progress signal 20 sha be transmitted immediately before the clearing signal but after the reception confirmation signal and the network identification signal (if any). 2 Recommendation U.101 (03/93) ITU-T RECMN*
32、U*LOL 93 - 4862593 0588796 TLB 1.2.4 If no reception confirmation or reception congestion signal is received within four seconds from the start of the calling signal, and no head-on collision has been detected, the call shall be cleared, the circuit shall be marked unavailable for outgoing traffic a
33、nd the automatic retest procedure shall be applied to the circuit concerned. 1.2.5 Selection signals are divided into two parts. The first part, designated as network selection signals, contains information regarding network and customer requirements and may comprise one or more characters (see Tabl
34、es 2, 3, 3a, 4, 4a and 5). The second part comprises address signals (the called customer number, preceded by the telex destination code on transit calls). The network selection signals are subdivided and assembled as described in 1.2.5.1 to 1.2.5.4 below for signalling purposes. 1.2.5.1 First class
35、-of-traffic character (see Table 2) The calling signal shall always be followed by at least one class-of-traffic character. The bit functions of this character are chosen so that no further network selection characters are required on the majority of calls. Whether a second class- of-traffic charact
36、er or a user-class character follows is indicated by bits b3 and b4 of the first class-of-traffic character. Bit bl of the first class-of-traffic indicates whether or not the address selection signals include a telex destination code. Bit b2 of the first class-of-traffic is used to indicate whether
37、or not the call may be subjected to alternative routing, see 1.1.5. 1.2.5.2 User-class characters (see Tables 3 and 3a) These characters, if used, shall follow the first class-of-traffic character and will be required when, for example, the information needed to be signalled cannot be derived from t
38、he incoming circuit. Bit b4 of the first user-class character is used to indicate whether or not a second class-of-traffic signal follows. 1.2.5.3 Second and third class-of-traffic characters (see Tables 4 and 4a) These characters, when used, shall follow either any user-class characters required, o
39、r when no user-class character is transmitted, the first class-of-traffic character. The number of class-of-traffic characters depends on the number of facilities available. Bit b4 of the second and subsequent class-of-traffic characters shall indicate whether a further class-of-traffic character fo
40、llows. Bit bl of the second class-of-traffic character shall indicate whether a call originates on a Type 1 or Type 2 network as defined in Recommendation U.201. 1.2.5.4 User group sequence A user group sequence, if required, shall follow after all class-of-traffic and user-class characters. Bit b3
41、of the second class-of-traffic character shall indicate whether or not a user group sequence is included in the network selection. The user group sequence shall comprise a start of user group character (see Table 5) followed by 1 to 8 hexadecimally coded user group characters. NOTE - The significanc
42、e of the user group sequence is for further study. 1.2.5.5 Address selection characters The numerical characters used for the address selection signals are detailed in Table 6. The first class-of-traffic character shall indicate whether or not this address selection includes a telex destination code
43、. 1.2.5.6 End of selection character The address selection signals shall be terminated by an end of selection character comprising IA5 character 2/11. Recommendation U.101 (03/93) 3 ITU-T RECMN*U-LOL 93 = 48b259L 0588797 954 1.2.6 Invalid selection signals received If the first character received af
44、ter detection of a calling signal is not a valid first class-of-traffic character, or has parity error, the incoming switching centre shall maintain start polarity on the backward signalling path. If any network selection signal after the first class-of-traffic character is not valid or has incorrec
45、t parity, or if any address selection character is received with incorrect parity, the incoming switching centre shall transmit call progress signal 20 followed immediately by a clearing signal. If the end of selection signal is not received within 15 seconds from reception of the first class-of-tra
46、ffic character, or if more than ten seconds elapses between consecutive selection characters, the incoming switching centre shall transmit call progress signal 20 followed immediately by a clearing signal. The call progress signai shall be transmitted after the reception confirmation signal and netw
47、ork identification signal (if 1 any). 1.2.7 The maximum number of address selection characters to be expected is 18. 1.2.8 signal 61 followed immediately by a clearing signal to the preceding centre. If the reception congestion signal is received at a transit centre, that transit centre shall transm
48、it call progress The call progress signal shall be transmitted after the reception confirmation signal and network identification signal (if any. 1.2.9 Network identification signais On calls incoming from international circuits the network identification signal shall be transmitted after the recept
49、ion confirmation signal. Network identification signals may be omitted by switching centres within a single network. NOTE - The nature of network identification signals to be transmitted from switching centres within a network is for further study. If several international centres are involved in the establishment of a call, the originating network will receive network identification signals one after another. If, at an international transit centre, the first character of a network identification signal is not received within two seconds of the reception confirmation signal, the incoming
