1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T Q.251-Q.300TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/1988) SERIES Q: SWITCHING AND SIGNALLING Specifications of Signalling System No. 6 ITU-T Recommendations Q.251-Q.300 (Formerly CCITT Recommendations) ITU-T Q-SERIES RECOMMENDATIONS SWITCHING A
2、ND SIGNALLING SIGNALLING IN THE INTERNATIONAL MANUAL SERVICE Q.1Q.3 INTERNATIONAL AUTOMATIC AND SEMI-AUTOMATIC WORKING Q.4Q.59 Basic Recommendations Q.4Q.9 Numbering plan and dialling procedures in the international service Q.10Q.11 Routing plan for international service Q.12Q.19 General Recommendat
3、ions relative to signalling and switching systems (national or international) Q.20Q.34 Tones for use in national signalling systems Q.35Q.39 General characteristics for international telephone connections and circuits Q.40Q.47 Signalling for satellite systems Q.48Q.49 Signalling for circuit multipli
4、cation equipment Q.50Q.59 FUNCTIONS AND INFORMATION FLOWS FOR SERVICES IN THE ISDN Q.60Q.99 Methodology Q.60Q.67 Basic services Q.68Q.79 Supplementary services Q.80Q.99 CLAUSES APPLICABLE TO ITU-T STANDARD SYSTEMS Q.100Q.119 General clauses Q.100Q.109 Transmission clauses for signalling Q.110Q.114 C
5、ontrol of echo suppressors Q.115 Abnormal conditions Q.116Q.119 SPECIFICATIONS OF SIGNALLING SYSTEMS No. 4 AND No. 5 Q.120Q.249 Specifications of Signalling System No. 4 Q.120Q.139 Specifications of Signalling System No. 5 Q.140Q.179 SPECIFICATIONS OF SIGNALLING SYSTEM No. 6 Q.250Q.309 SPECIFICATION
6、S OF SIGNALLING SYSTEM R1 Q.310Q.399 SPECIFICATIONS OF SIGNALLING SYSTEM R2 Q.400Q.499 DIGITAL EXCHANGES Q.500Q.599 INTERWORKING OF SIGNALLING SYSTEMS Q.600Q.699 SPECIFICATIONS OF SIGNALLING SYSTEM No. 7 Q.700Q.799 Q3 INTERFACE Q.800Q.849 DIGITAL SUBSCRIBER SIGNALLING SYSTEM No. 1 Q.850Q.999 PUBLIC
7、LAND MOBILE NETWORK Q.1000Q.1099 INTERWORKING WITH SATELLITE MOBILE SYSTEMS Q.1100Q.1199 INTELLIGENT NETWORK Q.1200Q.1699 SIGNALLING REQUIREMENTS AND PROTOCOLS FOR IMT-2000 Q.1700Q.1799 SPECIFICATIONS OF SIGNALLING RELATED TO BEARER INDEPENDENT CALL CONTROL (BICC) Q.1900Q.1999 BROADBAND ISDN Q.2000Q
8、.2999 For further details, please refer to the list of ITU-T Recommendations. Signalling System No. 6 (1988) i ITU-T Recommendations Q.251-Q.300 Specifications of Signalling System No 6 Summary Signalling System No. 6 could be used to control the switching of all types of international circuits, inc
9、luding TASI-derived circuits and satellite circuits. It is designed for both-way operation of the speech circuits. The system can also be used for regional and national applications, and a large part of the signal code capacity is reserved for this purpose. The system features are obtained by entire
10、ly removing the signalling from the speech paths and introducing the concept of a separate common signalling link over which all signals for a number of speech circuits are transferred. A number of these common signalling links interconnected by a number of transit centres and signal transfer points
11、 will form a coherent signalling network which can transfer all signals for all speech circuit groups within that network area. The separate common signalling link is capable of operation over both analogue and digital circuits. Signalling information is transmitted in the serial data mode on a link
12、-by-link basis i.e. the signals are transferred from one link to the next only after processing. Source ITU-T Recommendations Q.251-Q.300 were prepared by CCITT Study Group XI (1985-1988) and approved by WTSC in Melbourne on 25 November 1988. Those texts were originally published in Blue Book, Fasci
13、cle VI.3. ii Signalling System No. 6 (1988) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying te
14、chnical, 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, establishes the topics for study by the ITU-T study groups wh
15、ich, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSC Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO an
16、d IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommend
17、ations may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approv
18、al of this Recommendations, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendations. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB
19、patent database. ITU 2002 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Signalling System No. 6 (1988) iii CONTENTS Part I Specifications of Signalling System No. 6 Rec. No. Page INTRODUCTION. 1 SECTION 1 Fun
20、ctional description of the signalling system Q.251 1.1 General 3 Q.252 1.2 Signal transfer time definitions. 6 Q.253 1.3 Association between signalling and speech networks 7 SECTION 2 Definition and function of signals Q.254 2.1 Telephone signals . 10 Q.255 2.2 Signalling-system-control signals. 14
21、Q.256 2.3 Management signals . 15 SECTION 3 Signal unit formats and codes Q.257 3.1 General 16 Q.258 3.2 Telephone signals . 20 Q.259 3.3 Signalling-system-control signals. 28 Q.260 3.4 Management signals . 31 SECTION 4 Signalling procedures Q.261 4.1 Normal call set-up. 36 Q.262 4.2 Analysis of dig
22、ital information for routing . 42 Q.263 4.3 Double seizing with both-way operation 42 Q.264 4.4 Potential for automatic repeat attempt and re-routing. 43 Q.265 4.5 Speed of switching and signal transfer in international exchanges. 44 Q.266 4.6 Blocking and unblocking sequences and control of quasi-a
23、ssociated signalling 44 Q.267 4.7 Unreasonable and superfluous messages 46 Q.268 4.8 Release of international connections and associated equipment. 49 SECTION 5 Continuity check of the speech path Q.271 5.1 General 54 5.2 Reliability of the speech path across the exchange. 54 5.3 Continuity check of
24、 the speech circuit between exchanges 54 5.4 Loop checking method 54 5.5 Transmission requirements for the continuity check 54 5.6 Continuity signal. 55 5.7 Timing considerations for the continuity check 55 iv Signalling System No. 6 (1988) Rec. No. Page SECTION 6 Signalling link Q.272 6.1 Requireme
25、nts for the signalling data link . 57 Q.273 6.2 Data transmission rate. 62 Q.274 6.3 Transmission methods 63 6.4 Modem and interface requirements. 64 Q.275 6.5 Data channel failure detection 71 Q.276 6.6 Service dependability 71 Q.277 6.7 Error control 72 Q.278 6.8 Synchronization 75 Q.279 6.9 Drift
26、 compensation . 78 SECTION 7 Signal traffic characteristics Q.285 7.1 Signal priority categories 79 Q.286 7.2 Signalling channel loading and queueing delays 80 Q.287 7.3 Signal transfer time requirements . 84 SECTION 8 Security arrangements Q.291 8.1 General 87 8.2 Basic security arrangements . 87 8
27、.3 Types of failure, recognition of failure and abnormal error rates . 88 Q.292 8.4 Reserve facilities provided 90 Q.293 8.5 Intervals at which security measures are to be invoked 92 8.6 Changeover and changeback procedures 93 8.7 Emergency restart procedure 96 8.8 Full-time synchronized reserve lin
28、ks 98 8.9 Load sharing method 99 SECTION 9 Testing and maintenance Q.295 9.1 Overall tests of Signalling System No. 6 100 9.2 Signalling data link . 101 9.3 (Reserved). 102 9.4 (Reserved). 102 9.5 Network maintenance . 102 Q.296 9.6 Monitoring and maintenance of the common signalling channel . 105 S
29、ignalling System No. 6 (1988) v Rec. No. Page SECTION 10 Network management Q.297 10. Network management. 112 10.1 General 112 10.2 Information categories 112 Annex The application of network management signals transported by System No. 6 113 Annex A to Signalling System No. 6 specifications 115 Ann
30、ex B to Signalling System No. 6 specifications 121 Part II Interworking between CCITT Signalling System No. 6 and national common channel signalling systems Q.300 Interworking between CCITT Signalling System No. 6 and national common channel signalling systems 127 Glossary of terms specific to Signa
31、lling System CCITT No. 6 . 132 Abbreviations specific to Signalling System No. 6 . 136 Signalling System No. 6 (1988) 1 PART I SPECIFICATIONS OF SIGNALLING SYSTEM No. 6 Preamble This specification of Signalling System No. 6 represents an evolution originating with the Green Book text and proceeding
32、through the Yellow Book revision to the present text. It is intended that new or modernized application of System No. 6 should be based on this text. Updating of earlier versions is encouraged with the caution that careful coordination is called for. INTRODUCTION General Signalling System No. 6 can
33、be used to control the switching of all types of international circuits to be used in a worldwide connection, including TASI-derived circuits and satellite circuits. The system meets all requirements defined by the CCITT concerning the service features for world-wide international semi-automatic and
34、 automatic telephone traffic. It is designed for both-way operation of the speech circuits. The system can also be used for regional and national applications, and a large part of the signal code capacity is reserved for this purpose. Moreover, a large unused signal code capacity will allow the addi
35、tion of new signals to cater for some unknown future requirements. This spare capacity may be used for increasing the number of telephone signals as well as for introducing other signals, e.g. network-management signals and network-maintenance signals. The system features are obtained by entirely re
36、moving the signalling from the speech paths and introducing the concept of a separate common signalling link over which all signals for a number of speech circuits are transferred. A number of these common signalling links interconnected by a number of transit centres and signal transfer points will
37、 form a coherent signalling network which can transfer all signals for all speech circuit groups within that network area. Modes of operation The signalling system may be operated both in an associated mode and in a non-associated mode. In the associated mode of operation, the signals are transferre
38、d between the two exchanges which are the end points of a group of speech circuits over a common signalling link terminating at the same exchanges. In the non-associated mode of operation, the signals are transferred via two or more common signalling links in tandem associated with other groups of c
39、ircuits, the signals being processed and forwarded through one or more intermediate exchanges acting only as signal transfer point. The associated mode of operation is suited for use with large circuit groups, while a non-associated mode makes the signalling system economically suitable for use with
40、 small circuit groups by sharing the capacity of a signalling link among several groups. A signalling link may be operated in the associated mode for one circuit group and in a non-associated mode for other circuit groups, either under normal or under breakdown conditions. 2 Signalling System No. 6
41、(1988) Common signalling link The separate common signalling link is capable of operation over both analogue and digital circuits. Signalling information is transmitted in the serial data mode on a link-by-link basis i.e. the signals are transferred from one link to the next only after processing. A
42、nalogue signalling links are capable of operations over standard international voice bandwidth channels including the 3-kHz spaced telephone channels used for some intercontinental circuits. Over voice-frequency channels the stream of pulses is normally transmitted at a rate of 2400 bit/s using the
43、four-phase modulation method. With respect to digital signalling links, the 1544 kbit/s and 2048 kbit/s internationally standardized PCM primary multiplexes (Recommendation Q.47 and Recommendation Q.46) are treated differently. In the case of 1544 kbit/s a channel is derived over which the stream of
44、 pulses is transmitted at 4 kbit/s. Signalling information is also transmitted at 4 kbit/s. In the case of 2048 kbit/s, a channel is derived over which the stream of pulses is transmitted at 64 kbit/s. Signalling information may be sent over such a channel at specified rates of either 4 kbit/s or 56
45、 kbit/s. Other bit rates may have application in the future and other provisions for channel derivation may also prove useful, but neither are included in the present specification. In both analogue and digital channels the pulse stream is divided into signal units of 28 bits each and into blocks of
46、 12 signal units each. The error control necessary for a common signalling link is based on error detection by coding and on error correction by retransmission. Error detection is based on decoding of checking bits included in each signal unit and on data carrier failure detection. This provides the
47、 desired system reliability. Error-free signal messages are used without delay. Provision is made for automatic transfer to an alternative link in the event of failure caused by breakdown or excessive error rate. Signal messages Signal messages carry information to identify the telephone circuit con
48、cerned. Since the circuit identity, i.e. the label, requires a large proportion of the bits (11 out of the 20 available information bits), provision is made for sending multi-unit messages consisting of several signal units under one label. A single digit or a random telephone signal will normally b
49、e transferred in a one-unit message while several or even all digits may be transferred in a multi-unit message. Signal processing All signals are processed at each transit centre or signal transfer point which has to be passed. The processing of messages at a signal transfer point is minimal and includes label translation, if necessary, and the sending of signal messages within the proper priority category. In addition to the processing required at a signal point, a transit centre examines suffic
