1、STD*ITU-T RECMN E=ZL-ENGL 1999 48b2591 Obb1157 5T4 INTERNATIONAL TELECOMMUNICATION UNION ITURT TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU E.721 (05/99) SERIES E: OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS Quality of service, network management and traffic
2、engineering - Traffic engineering - ISDN traffic engineering Network grade of service parameters and target values for circuit-switched services in the evolving ISDN ITU-T Recommendation E.721 (Previously CCIlT Recommendation) ITU-T E-SERIES RECOMMENDATIONS OVERALL NETWORK OPERATION, TELEPHONE SERVI
3、CE, SERVICE OPERATION AND HUMAN FACTORS OPERATION, NUMBERING, ROUTING AND MOBILE SERVICES INTERNATIONAL OPERATION Definitions General provisions concerning Administrations General provisions concerning users Operation of international telephone services Numbering plan of the international telephone
4、service International routing plan Tones in national signalling systems Maritime mobile service and public land mobile service OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE Charging in the international telephone service Measuring and recording cal
5、l durations for accounting purposes UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON- TELEPHONY APPLICATIONS General Phototelegraphy ISDN PROVISIONS CONCERNING USERS QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING NETWORK MANAGEMENT International service statistics Internati
6、onal network management Checking the quality of the international telephone service TRAFFIC ENG1 N EERI NG Measurement and recording of traffic Forecasting of traffic Determination of the number of circuits in manual operation Determination of the number of circuits in automatic and semi-automatic o
7、peration Grade of service Definitions E. 1 OO-E. 103 E. 104-E. 1 19 E. 120-E. 139 E. 140-E. 159 E. 160-E. 169 E.? 70-E.179 E. 180-E. I99 E.200-E.229 E.230-E.249 E.260-E.269 E.300-E.319 E. 320-E. 329 E.330-E.399 E.400-E.409 E .4 1 0-E.4 1 9 E.420-E.489 E.490-E.505 E.506-E.509 E.510-E.519 E.520-E.539
8、E. 540-E. 599 E.600-E.699 Mobile network traffic engineering E.750-E.799 QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING Terms and definitions related to the quality of telecommunication services E.800-E.809 Models for telecommunication services E.810-E
9、.844 Objectives for quality of service and related concepts of telecommunication services Field data collection and evaluation on the performance of equipment, networks and services E.845-E.859 E.880-E.899 Use of quality of service objectives for planning of telecommunication networks E.860-E.879 Fo
10、r further details, please refer to ITU-T List of Recommendations. STD-ITU-T RECMN E.721-ENGL 1797 I 4862573 Ohhl359 377 m ITU-T RECOMMENDATION E.721 NETWORK GRADE OF SERVICE PARAMETERS AND TARGET VALUES FOR CIRCUIT-SWITCHED SERVICES IN THE EVOLVING ISDN Summary This Recommendation provides network G
11、rade of Service (GOS) parameters for circuit-switched services in ISDN, based on the ISDN Grade of Service concept and guidelines for selecting GOS parameters provided in Recommendation E.720. The parameter values assume that the network and the components are fully operational and take account of t
12、he evolving nature of the ISDN and Signalling System No. 7 capabilities. This version of this Recommendation includes revised parameters for GOS target values for circuit- switched services in the evolving ISDN. Source ITU-T Recommendation E.721 was revised by ITU-T Study Group 2 (1 997-2000) and wa
13、s approved under the WTSC Resolution No. 1 procedure on the 10th of May 1999. Recommendation E.721 (05/99) i FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a
14、 permanent organ of the ITU. 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
15、 years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recornmendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which
16、 fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation the term recognized operating agency (ROA) includes any individual, company, corporation or governmental organization that operates a public correspondence service
17、. The terms Administration, ROA and public correspondence are defined in the Constitution of the ITU (Geneva, 1992). INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Proper
18、ty Right. The IT 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 approval of this Recommendation, the ITU had not received noti
19、ce of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. O IT 1999 All rights reserved. No par
20、t 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 IT. 11 Recommendation E.721 (05/99) STDmITU-T RECMN E.721-ENGL 1999 W 48b2591 ObbL1bl T25 II CONTENTS Page 1 Introdu
21、ction 2 Circut-switched services 2.1 pre-selection delay (overlap sending) . 2.2 post-selection delay 2.3 answer signai delay . probability of end-to-end blocking . 2.4 call release delay . 2.5 3 Target values for GOS parameters . 4 Recommendation history 1 2 2 3 3 3 3 5 . Recommendation E.721 (05/9
22、9) 111 STD-ITU-T RECMN E.72L-ENGL 3999 = 48b259L ObbLLb2 9bL H Recommendation E.721 NETWORK GRADE OF SERVICE PARAMETERS AND TARGET VALUES (revised in 1999) FOR CIRCUIT-SWITCHED SERVICES IN THE EVOLVING ISDN 1 Introduction This Recommendation provides network Grade of Service (GOS) parameters for cir
23、cuit-switched services in ISDN, based on the ISDN Grade of Service concept and guidelines for selecting GOS parameters provided in Recommendation E.720. The parameter values assume that the network and the components are fully operational and take account of the evolving nature of the ISDN and Signa
24、lling System No. 7 capabilities. NOTE - GOS parameters and their target values for such services as point-to-multipoint, multislot services and reservation services require further study. Besides the E.700-series of Recommendations (ISDN traffic engineering) and Recommendations ES00 and E.502 (Measu
25、rement and recording of traffic), the following Recommendations also contain material that either provide background for or is relevant to this Recommendation: - - - - - CCITT Recommendation E. 172 (1 992), ISDN routing plan. ITU-T Recommendation G. 1 O1 (1 996), The transmission plan. CCITT Recomme
26、ndation 1.324 (1 99 1), ISDN network architecture. ITU-T Recommendation 1.325 (I 993), Reference configurations for ISDN connection types. ITU-T Recommendation 1.350 (1993), General aspects of quality of service and network performance in digital networks, including ISDN. ITU-T Recommendation 1.3 52
27、 (1 993), Network performance objectives for connection processing delays in an ISDN. ITU-T Recommendation 4.543 (1 993), Digital exchange performance design objectives. ITU-T Recommendation 4.706 (1 993), Message transfer part signalling performance. ITU-T Recommendation 4.709 (1 993), Hypothetical
28、 signalling reference connection. ITU-T Recommendation 4.766 (1 993), Performance objectives in the integrated services digital network application, ITU-T Recommendation 4.921 (1997), ISDN user-network interface - Data link layer specification. ITU-T Recommendation 4.93 1 (1 998), ISDN user-network
29、interface layer 3 specijication for basic call control. The relation with Recommendation 1.352 is particularly important. The major distinctions between this Recommendation and Recommendation 1.352 are: - The GOS values of this Recommendation are intended to be used for network dimensioning and thus
30、 consider the network to be in a state where all components are fully operational. Recommendation 1.3 52 identifies network performance objectives observable at specified network boundaries and includes the effects of both congestion and network failures. - - - - - - - Recommendation E.721 (05/99) 1
31、 STD-ITU-T RECMN E-72L-ENGL L999 I 48b2591i ObbLLb3 8T8 I - Since the parameters of this Recommendation are used for network dimensioning, trafic weighted averages of connection types are employed. On the other hand, 1.352 performance objectives characterize the performance any connection should ach
32、ieve and thus are upper bounds. The recommended values of this Recommendation allow for additional delays from connections that may include PSTN components which may be present during ISDN evolution. 1.352 values apply for an exclusively ISDN connection. - 2 Circuit-switched services In the current
33、ISDN specifications, call establishment and release for all circuit-switched services provided via B-channels (voice, data, image) will use the out-of-band call control procedures defined by Recommendation 4.93 1 and Signalling System No. 7 signalling protocols. The following traffic GOS parameters
34、are recommended for circuit-switched calls in ISDN: 1) pre-selection delay (overlap sending); 2) post-selection delay (overlap sending); 3) post-selection delay (en-bloc sending); 4) answer signal delay; 5) call release delay; and 6) probability of end-to-end blocking. The definitions of these traff
35、ic GOS parameters are given below. The delay GOS parameters are based on the message flows in Recommendation 4.931 and Signalling System No. 7 (ISUP) protocols as indicated, for example, in Figure A-1E.713. Further, delays or blocking within the customer premises equipment or subscriber terminal are
36、 not part of the following definitions for GOS parameters. 2.1 pre-selection delay (overlap sending) Pre-selection delay (overlap sending) is defined as the time interval from the instant the first bit of the SABME message is passed by the calling terminal to the access signalling system until the l
37、ast bit of the SETUP ACK message is received by the calling terminal. 2.2 post-selection delay a) post-selection delay (overlap sending) Post-selection delay (overlap sending) is defined as the time interval from the instant the first bit of the INFORMATION message containing the last selection digi
38、t is passed by the calling terminal to the access signalling system until the last bit of the first message indicating call disposition is received by the calling terminal (ALERTING message in case of successful call). post-selection delay (en bloc sending) Post-selection delay (en bloc sending) is
39、defined as the time interval from the instant the first bit of the initial SETUP message containing all the selection digits is passed by the calling terminal to the access signalling system until the last bit of the first message indicating call disposition is received by the calling terminal (ALER
40、TING message in case of successful b) call). 2 Recommendation E.721 (0999) STDmITU-T RECMN E-72l-ENGL 3999 E 4862592 Obbllb4 734 .I NOTE-In case of automatic answering terminals the ALERTING message is replaced by the CONNECT message. 2.3 answer signal delay Answer signal delay is defined as the tim
41、e interval from the instant that the called terminal passes the first bit of the CONNECT message to its access signalling system until the last bit of the CONNECT message is received by the calling terminal. 2.4 call release delay Call release delay is defined as the time interval from the instant t
42、he first bit of the DISCONNECT message is passed by the user terminal which terminated the call to the access signalling system, until the last bit of the RELEASE message is received by the same terminal (indicating that the terminals can initiatelreceive a new call). 2.5 probability of end-to-end b
43、locking The probability of end-to-end blocking is the probability that any call attempt will be unsuccessful due to a lack of network resources. NOTE 1 -Blocking because of lack of B-channels between the customer premises equipment and the network is not part of this definition. NOTE 2 - The lack of
44、 control plane resources during the call setup phase may also contribute to end-to-end blocking. This aspect is for further study. 3 The target values will be specified at the normal and high loads in the same sense as Recommendation E.500. However, additional study is required to ensure their suita
45、bility for ISDN. The delay target values will be specified by the mean and percentile levels for both normal and high loads. 3.1 PSTN users distinguish the following three types of service in their perfonnance expectations: - local service; - - international service. Local service is provided by net
46、works of one node in the simplest case, two nodes and one inter- office link in the most common case but up to six nodes in extreme and very rare cases. Typical local service can be represented by connections ranging from one to four nodes. Toll (or trunk) service is normally provided by a connectio
47、n involving at least four nodes (two local exchanges and two toll exchanges). Much longer connections are possible for the very small portion of traffic that would follow the all final route path in a multilevel hierarchical network. Both unusually short (e.g. combined local-toll exchanges) and unus
48、ually long connections should be ignored leading to toll service being represented by connections with five to seven nodes. Target values for GOS parameters toll (trunk) service within a country; and Recommendation E.721 (05/99) 3 Recommendation G. 1 O 1 gives connections for international service a
49、nd identifies the extreme cases as a 14-node connection. Recornmendation G. 1 O 1 also provides distributions of connection lengths based on measurements taken a number of years ago. In these measurements, 93% of calls used seven or less nodes and 99.98% used 11 or less nodes. Based on these distributions, connections for international service can be considered to include eight to ten nodes. The typical connections for ISDN circuit switched calls that have been used to establish the end-to- end GOS targets are summarized in Table 1. Number of nodes Local Toll International conne
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