1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU E.527 (03/2000) SERIES E: OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS Quality of service, network management and traffic engineering - Traffic engineering - Determination
2、 of the number of circuits in automatic and semi-automatic ope rat ion Dimensioning at a circuit group with multi-slot bearer services and overflow traffic ITU-T Recommendation E527 (Formerly CCITT Recommendation) ITU-T E-SERIES RECOMMENDATIONS OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE O
3、PERATION AND HUMAN FACTORS OPERA TION, 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 service Inte
4、rnational routing plan Tones in national signalling systems Numbering plan of the international telephone service Maritime mobile service and public land mobile service OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE Charging in the international tel
5、ephone service Measuring and recording call durations for accounting purposes UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON- TE LEP H ONY AP PLI CATI ONS General Phototelegraphy International routing plan QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING NETWORK MANAGEMENT
6、ISDN PROVISIONS CONCERNING USERS International service statistics International network management Checking the quality of the international telephone service TRAFFIC ENGINEERING Measurement and recording of traffic Forecasting of traffic Determination of the number of circuits in manual operation D
7、etermination of the number of circuits in automatic and semi-automatic operation Grade of service Definitions ISDN traffic engineering Mobile network traffic engineering QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING Terms and definitions related to th
8、e quality of telecommunication services Models for telecommunication services Objectives for quality of service and related concepts of telecommunication services Use of quality of service objectives for planning of telecommunication networks Field data collection and evaluation on the performance o
9、f equipment, networks and services E. 1 00-E. 103 E.104-E.119 E. 120-E. 139 E. 140-E. 159 E. 160-E. 169 E. 170-E. 179 E. 180-E. 189 E. 190-E. 199 E.200-E.229 E.230-E.249 E.260-E.269 E.300-E.319 E.320-E.329 E.350-E.399 E.400-E.409 E.41 0-E.419 E.420-E.489 E.490-E.505 E.506-E509 E.510-E519 E.540-E599
10、E.600-E.699 E.700-E.749 E.750-E.799 E.800-E.809 E.810-E.844 E.845-E.859 E.860-E.879 E.880-E.899 For further details, please rer to ITD-T List of Recommendations. ITU-T RECOMMENDATION E.527 DIMENSIONING AT A CIRCUIT GROUP WITH MULTI-SLOT BEARER SERVICES AND OVERFLOW TRAFFIC Summary This Recommendatio
11、n deals with dimensioning methods for a set of circuit groups handling multi- slot bearer services which consist of first-choice groups and an overflow group to which overflow traffic fiom the first-choice groups are offered. For this purpose, this Recommendation provides example methods for calcula
12、ting peakedness of the overflow traffic and example methods for calculating individual call blocking probabilities of the overflow group. Source ITU-T Recommendation ES27 was revised by ITU-T Study Group 2 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on 13 March 2000. Recom
13、mendation ES27 (03/2000) 1 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 permanent organ of the ITU. The ITU-T is responsible for studying technical, oper
14、ating 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 which, in their
15、 turn, produce Recommendations 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 fall within ITU-Ts purview, the necessary standards are prepared on a collaborativ
16、e basis with IS0 and 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 The ITU draws attention to the possibility that the practice or implement
17、ation of this Recommendation may involve the use of a claimed Intellectual Property Right. The 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
18、. As of the date of approval of this Recommendation, the ITU had not received notice 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 strong
19、ly urged to consult the TSB patent database. o ITU 2000 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 fi-om the ITU. 11 Recommendation ES27 (03/
20、2000) CONTENTS 1 2 3 4 5 5.1 5.2 5.3 6 6.1 6.2 7 7.1 7.2 8 9 Scope of this Recommendation References . Terms and definitions . Introduction . Modelling for dimensioning of circuit groups Modelling of offered traffic Categories of circuit groups GOS objectives . Characterization of overflow traffic r
21、om a first-choice group . Calculating traffic intensity of individual overflow Calculating peakedness of individual overflows Dimensioning methods for an overflow group . Principles Calculating individual call blocking probabilities History . Bibliography Annex A . Example methods for calculating ov
22、erflow variances rom a first-choice group A . 1 Assumptions and notations . A.2 Variance calculation methods . A.2.1 Exact solution method . A.2.2 Approximation method Annex B - Example method for calculating individual call blocking probabilities of an overflow group B.l Reduced network method . B.
23、2 Notations . B.3 Determination of equivalent capacity ni . B.4 Time congestion n B.5 Blocking probability Bi . B.6 The second overflow . B.7 Field of application . B.8 Processing time and programming effort Recommendation ES27 (03/2000) Page 1 1 1 2 2 2 3 3 3 3 3 3 4 4 . 111 Recommendation E.527 DI
24、MENSIONING AT A CIRCUIT GROUP WITH MULTI-SLOT BEARER SERVICES AND OVERFLOW TRAFFIC (revised in 2000) 1 Scope of this Recommendation This Recommendation deals with dimensioning methods for a set of circuit groups handling multi-slot bearer services which consist of first-choice groups and an overflow
25、 group to which overflow traffic rom the first-choice groups are offered. For this purpose, this Recommendation provides example methods for calculating peakedness of the overflow traffic and example methods for calculating individual call blocking probabilities of the overflow group. 2 References T
26、he following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users o
27、f this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. - - ITU-T Recommendation ES24 (1 999), Overflow appr
28、oximations for non-random inputs. ITU-T Recommendation ES26 (1 993), Dimensioning a circuit group with multi-slot bearer services and no overjlow inputs. CCITT Recommendation E.73 1 (1992), Methods for dimensioning resources operating in circuit switched mode. - - ITU-T Recommendation E.737 (1 997),
29、 Dimensioning methods for B-ISDN. 3 Terms and definitions Recommendation E.600 provides general terminology in traffic engineering used in this Recommendation. 4 Introduction This Recommendation presents methods for dimensioning a circuit group with multi-slot bearer services and overflow traffic. M
30、ethods for dimensioning a circuit group with multi-slot bearer services and no overflow traffic are presented in Recommendation E.526. Thus this Recommendation complements Recommendation E.526. This Recommendation treats an overflow group to which multiple overflow traffic streams rom the first-choi
31、ce groups. It is assumed that both overflow groups and first-choice groups are operated with full availability (see Recommendation E.73 1). Individual traffic streams will be expressed, on the one hand, in calls as in Recommendation E.524, and on the other in busy circuits as in Recommendation E.526
32、. Recommendation ES27 (03/2000) 1 This Recommendation is also related to Recommendations E.73 1 and E.737 in that the dimensioning methods presented in these Recommendations are based on the technique of multi-slot traffic modelling of a circuit-switched network which handles a mixed traffic with di
33、fferent bandwidth requirements. 5 Modelling for dimensioning of circuit groups 5.1 Modelling of offered traffic For traffic engineering purpose, multi-slot bearer traffic is often characterized by the following parameters : - - - - - - traffic stream identification, denoted by i; call arrival rate f
34、or traffic stream i, denoted by hi; mean holding time for traffic stream i, denoted by l/pi; number of circuits occupied by a call for traffic stream i, denoted by di; traffic intensity measured in number of calls for traffic stream i, denoted by Ai (Ai = A peakedness factor for traffic stream i, de
35、noted by Zi. 5.2 Categories of circuit groups In this Recommendation, the following two categories of circuit groups with multi-slot bearer services are considered. a) First-choice group A first-choice group is a circuit group to which fi-esh traffic is offered. The fi-esh traffic is modelled by a P
36、oisson arrival process and thus its peakedness factor is one. The first-choice group with multi-slot bearer services may handle various traffic streams of calls which hold different numbers of time slots when accepted. Following the definitions and notations in Recommendation E.526, the size of the
37、first- choice group is represented by the number of circuits in the group. b) Overflow group An overflow group is a circuit group to which overflow traffic fi-om the first-choice groups is offered. It may handle fi-esh traffic which is offered to it as well. The size of the overflow group is also re
38、presented by the number of circuits in the group. 5.3 GOS objectives For the purpose of dimensioning circuit groups with multi-slot bearer services, call blocking probabilities are considered as an important GOS parameter. Thus, the objectives of link call blocking probabilities and/or end-to-end ca
39、ll blocking probabilities are often used in a dimensioning process of a network which consists of circuit groups. Since end-to-end call blocking probabilities are often calculated fi-om the link call blocking probabilities and routing patterns as described in Recommendation E.737, it is important to
40、 evaluate individual call blocking probabilities at a circuit group. This Recommendation, therefore, focuses on methods for calculating individual call blocking probabilities at the circuit group level. 2 Recommendation ES27 (03/2000) 6 Characterization of overflow traffic from a first-choice group
41、6.1 Once individual call blocking probabilities are obtained at a first-choice group, the traffic intensities Oi of individual overflows can be evaluated as follows: Calculating traffic intensity of individual overflow Oi = Ai Bi (6-1) where Bi denotes the call blocking probability of the i-th traff
42、ic stream at the first-choice group. Example methods for calculating the call blocking probability Bi are given in Recommendations E.526, E.73 1 and E.737. 6.2 To characterize the overflow traffic for the purpose of dimensioning the overflow group, the peakednesses of the individual overflow traffic
43、 offered to the overflow group are often used. The peakedness Zi is defined as: Calculating peakedness of individual overflows where fi denotes the variance of the overflow traffic. Example methods for calculating the variances and thus peakednesses of individual overflow are given in Annex A. 7 Dim
44、ensioning methods for an overflow group 7.1 Principles The basic problem of dimensioning an overflow group is to determine the size of the group and the parameter values of service protection schemes such as a trunk reservation (see Recommendations E.731 and E.737), if applied, under the constraint
45、of call blocking objectives in an economical way for a given offered traffic condition. Note that the overflow traffic streams offered to the group may be characterized by its traffic intensity and peakedness. If the overflow traffic is directly offered fiom a first-choice group, its intensity and p
46、eakedness may be calculated by using the methods given in clause 6. To dimension the overflow group, in principle, the following iterative procedure is used: Step 1: Start with an initial set of values of the group size and, if applied, of parameters of service protection schemes. Step 2: Evaluate i
47、ndividual blocking probabilities of the calls at the group for the current set of group size and parameter values to check if the blocking objectives are satisfied. Step 3: If the objectives are all met and a certain optimization criterion is met as well, end the procedure. Otherwise, modify the gro
48、up size and/or the parameter values of service protection schemes and return to Step 2. As seen in Step 2 above, it is needed to calculate all the call blocking probabilities for the group. 7.2 Several methods are available for calculating approximate individual call blocking probabilities at the ov
49、erflow group. Table A. UE.737 gives a (not exhaustive) list of available methods. Annex B gives another example method which is not included in Table A. UE.737. Calculating individual call blocking probabilities Recommendation ES27 (03/2000) 3 8 History The first issue in 1995, revised in 2000. 9 Bibliography i 2 3 ODA (T.): Moment Analysis for Traffic Associated with Markovian queueing Systems, IEEE Transactions on Communications, Vol. 39, No. 5, pp. 737-746, May 1991. LE GALL (P.): Overflow traffic combination and cluster engineering, Proceedings of ITC-11, paper 2.2 B-1, Kyoto 1
