1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU SPECIFICATIONS OF SIGNALLING SYSTEM No. 7 (2.709 (03/93) SIGNALLING SYSTEM NO. 7 - HYPOTHETICAL SIGNALING REFERENCE CONNECTION ITU-T Recommendation Q.709 (Previously “CCITT Recommendation”) ITU-T RECMN*Q.709
2、93 W 4862.593 0585004 995 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 standard
3、izing 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 4.709 was revised
4、 by the ITU-T Study Group XI (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 Standardi
5、zation 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 Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector.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 references containing the acronyms “CCI
6、TT, 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 exp
7、ression “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 permission in writing from the ITU. 4 5 I
8、TU-T RECMN*Q-709 93 48b259L 0585005 821 CONTENTS Introduction Requirements of networks served by the signalling connection HSRC components for link-by-link signalling . 3.1 General 3.2 International component of HSRC . 3.3 National components of HSRC . Overall signalling delay for link-by-link signa
9、lling . HSRCcomponents for end-to-end signalling . 5.1 General 5.2 International component of HSRC . 5.3 National components of HSRC . 6 Overall signalling delay for end-to-end signalling . 7 Influence of new SS No . 7 applications . 7.1 7.2 Effects of message length and other variables 8 Remarks An
10、nex A - Database query considerations A.l General A.2 Delay formulae . A.3 Application . A.4 Reduction in User-Part delay allowance . References Effects of database queries . Page 1 1 1 1 2 3 4 6 6 6 8 8 8 8 9 10 10 10 10 12 13 14 Recommendation Q.709 (03/93) 1 ITU-T RECMNJQ-709 93 9 48b259L 058500b
11、 7bB 9 Recommendation Q.709 SIGNALLING SYSTEM NO. 7 - HYPOTHETICAL SIGNALLING REFERENCE CONNECTION (Malaga-Torremolinos, 1984; modified at Helsinki, 1993) 1 Introduction This Recommendation specifies how the elements of a signalling connection from an originating node to a terminating node are combi
12、ned to meet the signalling requirements of the networks that it supports. Included are parameters for signalling transfer delay in both national and international networks, and overall signalling delay that such combinations will produce, together with the availability required, to enable the perfor
13、mance of the network served by the signalling network to be maintained. A probabilistic approach has been taken, i.e. limits are specified for 50% and 95% of connections. These figures will apply to the normal operation of a signalling network. No consideration is given to the “unusually long” signa
14、lling paths that are found in some signalling networks. Any unusual routing caused by some network structures andfor reconfigurations due to network failure are considered to be covered in the remaining 5% of connections. The hypothetical signalling reference connection (HSRC) for international work
15、ing is specified in this Recommendation by defining the constituent parts of i) one international section; and ii) two national sections. When combing the sections to produce an overall HSRC, it is necessary to consider what impact each of the three component parts have on each other and the full HS
16、RC. This means that certain national or international limits such as the maximum number of signalling transfer points allowed in a signalling relation (see 5.2/Q.705) may require modification and account of this has been taken in this Recommendation. The effect on the HSRC of larger message sizes (s
17、ee 7.2) and database queries due to new SS No. 7 applications are also considered (see Annex A). 2 Requirements of networks served by the signalling connection To meet the requirements of services carried on the network served by the signalling network, the signalling connection performance should b
18、e closely aligned with those requirements. Since these services are ultimately to be carried on an ISDN, the HSRC is based upon the hypothetical reference connection developed for ISDN network (see Recom- mendation G.801). Account must also be taken of the service requirements in Recommendations E.7
19、21, E.723 and 1.352. However, for a considerable time the majority of services in the network served by the signalling network will be telephony-based and account must therefore be taken of the reference connection for conventional telephony application (see Recommendation G.lO1). 3 HSRC components
20、for link-by-link signalling 3.1 General The components of a HSRC are signalling points and STPs which are connected in series by signalling data links to produce a signalling connection (see Note 1). The number of signalling points and STPs depend on the size and structure of the network. Two limits
21、 are prescribed to cover 50% and 95% of cases. Separate cases are allowed for large-size countries and average-size countries (see Note 2). This clause outlines the considerations involved in formulating a HSRC for link-by-link signalling and details the number of HSRC components and the delays they
22、 produce. Recommendation Q.709 (03/93) 1 NOTES 1 The term signalling point is used to designate use of a user function in a signalling point: whether or not STP function is present is irrelevant in this context. The term STP is used to designate use of the STP function in a signalling point: whether
23、 or not a user function is present is irrelevant in this context. When the maximum distance between an international switching centre and a subscriber who can be reached from it does not exceed loo0 km or, exceptionally, 1500 km, and when the country has less than n x lo7 subscribers, the country is
24、 considered to be of average-size. A country with a larger distance between an international switching centre and a subscriber, or with more than n x lo7 subscribers, is considered to be of large-size. (The value of n is for further study.) 2 3.1.1 Number of signalling points in the HSRC The number
25、of signalling points in the HSRC has been determined by considering the maximum number of links allowed by the Telephone Routing Plan (see Recommendation E. 171). These Recommendations define “last choice” backbone routes and only a small proportion of traffic take these routes. Traffic generated in
26、 metropolitan areas, generally the largest source of traffic, usually takes far fewer links to an international switching centre. Even for rural areas a connection to the international switching centre will not generally be required to follow the backbone route. Limiting the number of signalling poi
27、nts required will reduce the signalling delay, because signalling point delay forms the largest component of signalling delay. 3.1.2 Number of STPs in a HSRC The number of STPs in a HSRC is a function of the number of signalling points, and the signalling network topology used to connect these signa
28、lling points. The number of STPs should be kept to a minimum in order to limit the signalling delay. In some signalling relationship, associated signalling may be used for which no STPs are required. In others, one or more STPs may be used. For international signalling relationship, it is recommende
29、d that no more than 2 STPs be used in a signalling relations (see 5.2/Q.705). 3.1.3 Signalling network availability The availability of a signalling connection is an important network parameter. It is necessary for the availability of the signalling connection to be significantly better than the ava
30、ilability of the component being controlled (e.g. a circuit). The total unavailability figure for any particular signalling route set (see 1. VQ.706) should not exceed: - 10 minutes per year. This corresponds to an availability of 0.99998, which can be achieved by the use of suitable network redunda
31、ncies. 3.1.4 Signalling message transfer delay Signalling message transfer delay is another important network parameter. It affects call set up delay and also affects network response time to service requests made during a call. Note that in this Recommendation, the transmission propagation delays a
32、re not included (see 7.2). 3.2 International component of HSRC The international component of the HSRC includes all international signalling points in the connection and the STPs carrying signalling messages between the signalling points. The maximum number of signalling points and STPs allowed are
33、listed in Table 1. The total unavailability of the overall international component of the signalling network should not exceed the following for both the 50 percent and 95 percent cases: - - - 20 minutes per year for large-size country to large-size country; 30 minutes per year for large-size countr
34、y to average-size country; and 40 minutes per year for average-size country to average-size country. The maximum signalling transfer delay under normal conditions for the international component of a connection should not be worse than the values listed in Table 2. 2 Recommendation 9.709 (03/93) ITU
35、-T RECMN*Q.709 93 q8b259L 0585008 530 9 Country size (Note 1) Large-size Large-size Large-size Average-size Average-size Average-size to to to Percent of Number of STPs Number of connections signalling points 50% 3 95% 4 50% 4 95% 4 50% 5 95% 7 3 4 5 TABLE 2/Q.709 Maximum signalling delays for inter
36、national component Simple (e.g. answer) Country size Processing intensive (e.g. IAM) Percent of connections Delay (ms) (Note 1) Large-size to Large-size 50% 95% 390 410 600 620 Large-size to Average-size 50% 95% 520 540 800 820 Average-size Average-size to 50% 95% 650 690 lo00 1 o40 NOTES 1 Only the
37、 mean delay component from Table 51Q.706, Table 3/Q.725 and Table UQ.766 have been used in calculating the delay. Further study is required, eg. for the mean values as weil as the inclusion of overload and/or 95 percentile cases of each component value. 2 See clause 7. 3.3 National components of HSR
38、C The national components of the HSRC includes all national exchanges in the connection (but does not include the international switching centre in the country) and all STPs carrying signalling messages between the national exchanges and between the highest level national exchange and the internatio
39、nal switching centre. The maximum number of signalling points and STPs allowed are listed in Table 3. Recommendation Q.709 (03/93) 3 ITU-T RECMN*Q.709 73 48b257L 0585007 477 m Percent of connections I Country size (Note 1) TABLE 3/4.709 Maximum number of signalling points and STPs in national compon
40、ents Number of STFs Number of signalling points 50% 95% 50% 95% Large-size Average-size 3 3 4 4 2 2 3 3 NOTES 1 See Note 2 to 3.1. 2 The values in this table are provisional. (A higher number of signalling points and/or STPs might be included in a national network, e.g. in the case that a two-level
41、hierarchical signalling network is adopted. This matter is for further sutdy.) 3 It is for further study how the QOS parameters in Recommendation E.721 can be achieved in networks that use a greater number of SWs. The unavailability of each of the overall national components of the signalling networ
42、k should not exceed the following totals per year: - 20 minutes for the 50% case of average-size countries; - 30 minutes for the 95% case of average-size countries and the 50% case of large-size countries; and - NOTES 40 minutes for the 95% case of large-size countries. 1 Although the signalling com
43、ponent of the intemational switching centre in the country was not included in Table 3, it is included in the unavailability objectives. 2 The HSRC defines a unique path through the national and international networks, therefore when considering the overall unavailability of each national component,
44、 no account is taken of any standby path, if provided, in that national network. The values given are based on those for each component route-set as specified in l.llQ.706. The maximum signalling transfer delay under normal conditions for each of the national components of a connection should not be
45、 worse than the values listed in Table 4. 4 Overall signalling delay for link-by-link signalling From the HSRC and the values of message transfer times given for signalling point and STP, the overall signalling delay due to Signalling point, and STF delays can be determined from Tables 2 and 4, for
46、a given load in a given network. Delays for 50% and 95% of connections are given in Table 5 for various combinations of large-size and average-size countries. Average signalling point and STP delays at normal loading are assumed. These values must be increased by the transmission propagation delays
47、(see Table VQ.41). Annex A considers the impact of database queries on the allowable link-by-link signalling delays. 4 Recommendation Q.709 (0-3) ITU-T RECMN*Q.707 73 = 4862591 0585010 199 Simple (e.g. answer) TABLE 4/4.709 Maximum signalling delays for each national component Processing intensive (
48、e.g. IAM) Country size Simple (e.g. answer) Large-size Average-size Processing intensive (e.g. IAM) Delay (ms) (Notes 1 and 2) Message type I Percent of connections 50% 95% 50% 390 520 260 600 800 400 600 I 390 I 95% NOTES 1 2 included in the international component. 3 See clause 7. See Note to Tabl
49、e 2. The delay does not include any delay for the International Switching Centre in the country, which is TABLE 5lQ.709 Maximum overall signalling delays Country size Large-size to Large-size Large-size to Average-size Average-size Average-size NOTES 1 2 See clause 7. to See Note to Table 2. Percent of connections 50% 95 % 50% 95% 50% 95 % Delay (ms) (Note i) 1170 1450 1800 2220 1170 1450 1800 2220 1170 i 470 1800 2240 Recommendation Q.709 (03/93) 5 5 HSRC components for end-to-end signalling 5.1 General The components of a HSRC are signalling end points (SEP), signalling
