1、CCITT RECMN*E.723 92 4862593 0573743 456 CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE TELEPHONE NETWORK AND ISDN QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING E.723 GRADE-OF-SERVICE PAREMETERS FOR SIGNALLING SYSTEM No. 7 NETWORKS Recommendation E.723 CCITT
2、RECMN*E.723 92 M 4862593 0573742 392 M INTERNATIONAL TELECOMMUNICATION UNION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE TELEPHONE NETWORK AND ISDN QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING E.723 GRADE-OF-SERVICE PAREMETERS FOR SIGNALLING SYSTEM No. 7
3、NETWORKS Recommendation E.723 Geneva, 1992 FOREWORD The CCIT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the International Telecommunication Union (). CCIT is responsible for studying technical, operating and tariff questions and issuing Recommendations
4、 on them with a view to standardizing telecommunications on a worldwide basis. The Plenary Assembly of CCITT which meets every four years, establishes the topics for study and approves Recommendations prepared by its Study Groups. The approval of Recommendations by the members of CCI” between Plenar
5、y Assemblies is covered by the procedure laid down in CCm Resolution No. 2 (Melbourne, 1988). I Recommendation E.723 was prepared by Study Group II and was approved under the Resolution No. 2 procedure on the 16 of June 1992. CCIT NOTES 1) telecommunication Administration and a recognized private op
6、erating agency. 2) In this Recommendation, the expression “Administration” is used for conciseness to indicate both a A list of abbreviations used in this Recommendation can be found in Annex A. O ITU 1992 Ail rights reserved. No part of this publication may be reproduced or utilized in any form or
7、by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the RU. CCITT RECMN*E-723 92 m 4862571 0573744 Lb5 m Recommendation E.723 GRADEOF-SERVICE PARAMETERS FOR SIGNALLING SYSTEM No. 7 NETWORKS 1 Scope and objectives Based on the reference con
8、nections for ISDN circuit switched services and the grade-of-service (GOS) parameter values contained in Recommendation E.721, this Recommendation provides appropriate reference connections for the S.S. No. 7 network and identifies the signalling network GOS parameters and their target values. Furth
9、er, the Recommendation also provides guidelines for partitioninghllocafhg the signalling network end-to-end GOS to the basic components of the S.S. No. 7 network, The reference connection and GOS parameters and values for source transaction type services requiring data base lookup are also included.
10、 2 Reference connections for S.S. No. 7 networks Reference connections for ISDN circuit switched service are contained in Table 1b3.721 in terms of the number of switching nodes in local, toll or international connections. In the control plane, several configurations of signalling links and signal t
11、ransfer points (STPs) between the signalling points (SPs) associated with two adjacent nodes in the E.721 connections are possible. For example, the relations shown in Figure 1b3.723 may commonly exist. The configurations, on the following page, are consistent with Recommendation Q.709 and represent
12、 the basic segments of the S.S. No. 7 network. In this Recommendation therefore, the S.S. No. 7 end-to-end delay objectives are allocated per user plane circuit group (basic S.S. No. 7 network segment). Individual Administrations may choose the signalhg network configuration and the resulting sub-di
13、vision of delay objectives to signalling link-sets and STPs within a national network. The reference connections for the S.S. No. 7 network (i.e. the number of STPs) corresponding to Recommendation E.721, are shown in Table 11E.723. The signalling network configuration used as the reference connecti
14、on for a transaction type service requiring a single data base lookup is shown in Figure uE.723. Reference connections for more complicated intelligent network (IN) calls is for further study. 3 GOS parameters for S.S. No. 7 network 3.1 Two delay GOS parameters for ISDN circuit switched services tha
15、t depend on the performance of the S.S. No, 7 network include the post-selection delay and the answer signal delay. The target values (mean) for these are specified in Recommendation E.721 for local, toll and international reference connections under normal load (Table 2lE.721). 1 Throughout this Re
16、commendation the STP designation is used to denote either Message Transfer Part (MTP) processing capability or MTP and Signalling Connection Control Part (SCCP) processing capability. The MTP and SCCP protocols are defined in the Q.70-Series Recommendations. Recommendation E.723 1 2 - - - _ CCITT RE
17、CMN*E.723 92 4862571 0573745 OTL 1 signalling link set O STP 1 circuit group Per user plane 2 signalling link sets 1 STP 1 circuit group Per user plane 3 signalling link sets 2 STPs 1 circuit group Per user plane 4 signalling link sets 3 STPs 1 circuit group Per user plane ix Exchange 1/1 Signai tra
18、nsfer point (STP) Signalling link set _- User plane circuit group FIGURE 1B.723 Recommendation E.723 CCITT RECMN*E.723 92 4862593 0573746 T38 Number (n) of switching nodes in user plane from Rec. E.721 Number of STPs in S.S. No. 7 reference connection corresponding to the switching nodes in the user
19、 plane TABLE 1E.723 Reference connections for the SS. No. 7 network corresponding to the user plane reference connection for ISDN circuit switched services in Recommendation E.721 Connection type Local Toll International n=4 n=7 n= 10 3 8*) 12b) c a) The number of STPs in the reference connection is
20、 obtained by assuming that one STP exists between each pair of signalkg points (exchanges), and that two additional STPs exist somewhere in the reference connection. A variety of arrangements of STPs within the reference connection having the same number of STPs are possible. b) In addition to a), o
21、ne additional STP exists somewhere in the international part of the reference connection, It is also assumed that one of the signalling links is via satellite. FIGURE 2m.723 Reference connection for transaction type service using S.S. No. 7 network For specifying the end-to-end GS in a S.S. No. 7 ne
22、twork, the delay incurred by the most processing intensive message (i.e. the initiai address message (IAh4) in traversing the network is considered the most important GOS parameter. This delay is defined as the time interval from the instant that the first bit of the IAM message leaves the signaliin
23、g terminal until the last bit enters the terminating signalling terminai plus an allowance to account for the ISDN User Part (ISUP) and h4TP processing times and queuing delays of the S.S. No. 7 sub-system of the originating and terminating signalling terminals. The originating and terminating signa
24、liing terminals may be integrated with the originating and terminating exchanges. The second end-to-end GS parameter of interest is the delay incurred by the answer message (ANM). This delay is almost identicai (slightiy shorter) than the answer signal delay of Recommendation E.721. Recommendation E
25、.723 3 This delay is defined as the time interval from the instant that the fust bit of the ANM message leaves the Originating signalling terminai until the last bit enters the terminating signalling terminal plus an allowance to account for the ISTJP and MTP processing times and queueing delays of
26、the S.S. No. 7 sub-system of the originating and terminating signalling terminals. 3.2 The objective value for the total delay for IAM can be derived from Table 2E.721 by subtracting the objective for answer signal delay from post-selection delay (since the address complete delay is comparable to an
27、swer signai delay) and subtracting additional time to reflect some processing time at the originating and terminating exchanges and access delays. The values for the mean end-to-end IAM delay are shown in Table 2dE.723. TABLE 2E.723 Mean values for IAM end-toad delay for reference connections Mean d
28、elay (normal load) Connection type I 0.9 seconds I 2.3 seconds International 4.0 seconds The ANM delay objective value is specified the same as answer signal delay from Recommendation E.721. The values for the mean ANM delay are shown in Table 3B.723. TABLE 3E.723 Mean values for the ANM delay for r
29、eference connections Mean delay (normal load) Connection type Local 0.75 seconds Toli 1.50 seconds International 2.50 seconds 3.3 the SCP or the SP, is 0.8 seconds. The objective value for the mean round trip delay for SCP access, not including the application processing at 4 Recommendation E.723 CC
30、ITT RECMN*E.723 72 W 4862571 0573748 800 = Total delay International delay IAM 4.0 1.5 ANM 2.5 1.0 4 Partitioning GOS for signalling message delays National delay4 2.5 1.5 The partitioning of the IAM and ANM delays into national and international portions is based on the network model specified in T
31、able 1E.723. The allocation to network portions is done by considering the ratio of signalling links and STPs and the associated delays in the international part of the reference connection of Table 1E.723 to the total connection. The total IAM delay of 4.0 seconds and ANM delay of 2.5 seconds shoul
32、d be partitioned between the national and international portions of the S.S. No. 7 network as shown in Table 4E.723. 5 ANM GOS IAM IN ISUP MTP SCCP SCP SP STP Recommendation history Recommendation E.723 -First issue 1992. ANNEX A (to Recommendation E.723) Alphabetical list of abbreviations used in this Recommendation Answer message Grade-of-service Initial address message Intelligent network ISDN user part Message transfer part Signalling connection control part Service control point Signailing point Signal transfer point Recommendation E.723 5
