1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T E.490.1TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (01/2003) SERIES E: OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS Traffic engineering Measurement and recording of traffic Overview of Recommendations on traffic en
2、gineering ITU-T Recommendation E.490.1 ITU-T E-SERIES RECOMMENDATIONS OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS INTERNATIONAL OPERATION Definitions E.100E.103 General provisions concerning Administrations E.104E.119 General provisions concerning users E.120E.1
3、39 Operation of international telephone services E.140E.159 Numbering plan of the international telephone service E.160E.169 International routing plan E.170E.179 Tones in national signalling systems E.180E.189 Numbering plan of the international telephone service E.190E.199 Maritime mobile service
4、and public land mobile service E.200E.229 OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE Charging in the international telephone service E.230E.249 Measuring and recording call durations for accounting purposes E.260E.269 UTILIZATION OF THE INTERNAT
5、IONAL TELEPHONE NETWORK FOR NON-TELEPHONY APPLICATIONS General E.300E.319 Phototelegraphy E.320E.329 ISDN PROVISIONS CONCERNING USERS E.330E.349 INTERNATIONAL ROUTING PLAN E.350E.399 NETWORK MANAGEMENT International service statistics E.400E.409 International network management E.410E.419 Checking t
6、he quality of the international telephone service E.420E.489 TRAFFIC ENGINEERING Measurement and recording of traffic E.490E.505 Forecasting of traffic E.506E.509 Determination of the number of circuits in manual operation E.510E.519 Determination of the number of circuits in automatic and semi-auto
7、matic operation E.520E.539 Grade of service E.540E.599 Definitions E.600E.649 Traffic engineering for IP-networks E.650E.699 ISDN traffic engineering E.700E.749 Mobile network traffic engineering E.750E.799 QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNIN
8、G Terms and definitions related to the quality of telecommunication services E.800E.809 Models for telecommunication services E.810E.844 Objectives for quality of service and related concepts of telecommunication services E.845E.859 Use of quality of service objectives for planning of telecommunicat
9、ion networks E.860E.879 Field data collection and evaluation on the performance of equipment, networks and services E.880E.899 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. E.490.1 (01/2003) i ITU-T Recommendation E.490.1 Overview of Recommendations on traffic en
10、gineering Summary This Recommendation provides an overview of the Recommendations on Traffic Engineering, specifically those numbered between E.490 and E.799, which constitute the main body of ITU-T Recommendations on traffic engineering. This Recommendation presents the four major traffic engineeri
11、ng tasks, classifies the traffic engineering Recommendations according to the task to which they are related, provides a brief overview of each Recommendation and describes the interrelation between Recommendations. It is intended as an introduction for those practitioners who wish to apply ITU-T Re
12、commendations on traffic engineering. Source ITU-T Recommendation E.490.1 was prepared by ITU-T Study Group 2 (2001-2004) and approved under the WTSA Resolution 1 procedure on 13 January 2003. History This is the first issue of ITU-T Rec. E.490.1 ii ITU-T Rec. E.490.1 (01/2003) FOREWORD The Internat
13、ional 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 technical, operating and tariff questions and issuing Recommendatio
14、ns on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval
15、 of ITU-T Recommendations is covered by the procedure laid down in WTSA 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 and IEC. NOTE In this Recommendation, the expression “Administration“
16、 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 Recommendation may involve the use of a claimed Intellectual Property Right.
17、 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 approval of this Recommendation, ITU had not received notice of intellectu
18、al 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. ITU 2003 All rights reserved. No part of this publica
19、tion may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. E.490.1 (01/2003) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 4 Abbreviations 1 5 Major traffic engineering tasks. 2 6 Traffic demand characterization. 3 6.1 Traffic modelling 3 6
20、.2 Traffic measurements . 4 6.3 Traffic forecasting 6 7 Grade of service objectives. 7 8 Traffic control and dimensioning . 11 8.1 Circuit-switched networks 12 8.2 Packet-switched networks 14 8.3 Signalling and IN-structured networks. 15 9 Performance monitoring . 16 10 Other Recommendations 17 ITU-
21、T Rec. E.490.1 (01/2003) 1 ITU-T Recommendation E.490.1 Overview of Recommendations on traffic engineering 1 Scope This Recommendation provides an overview of the Recommendations on Traffic Engineering, specifically those numbered between E.490 and E.799, which constitute the main body of ITU-T Reco
22、mmendations on traffic engineering. It is intended as an introduction for those practitioners who wish to apply ITU-T Recommendations on traffic engineering. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute pro
23、visions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendat
24、ions and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. All the Recommendations between E.490 and E.799 are
25、referred to in this Recommendation. They are listed in Tables 1 to 7 and 9 to 12. 3 Definitions The terms used in these Recommendations are consistent with the definitions made in the referred Recommendations on traffic engineering, especially with those made in ITU-T Rec. E.600 Terms and definition
26、s of traffic engineering. 4 Abbreviations This Recommendation uses the following abbreviations: ANM Answer Message ARIMA Autoregressive Integrated Moving Average ATM Asynchronous Transfer Mode B-ISDN Broadband ISDN CAC Connection Admission Control CPN Customer Premises Network DCME Digital Circuit M
27、ultiplication Equipment GoS Grade of Service HFC Hybrid Fiber-Coaxial IAM Initial Address Message IN Intelligent Network IP Internet Protocol ISDN Integrated Services Digital Network N-ISDN Narrowband ISDN 2 ITU-T Rec. E.490.1 (01/2003) NP Network Performance PSTN Public Switched Telephone Network Q
28、oS Quality of Service SS No.7 Signalling System No.7 STP Signal Transfer Point UPT Universal Personal Telecommunication YRV Yearly Representative Value 5 Major traffic engineering tasks This Recommendation on traffic engineering can be classified according to the four major traffic engineer tasks: t
29、raffic demand characterization; Grade of Service (GoS) objectives; traffic controls and dimensioning; performance monitoring. The interrelation between these four tasks is illustrated in Figure 1. The initial tasks in traffic engineering are to characterize the traffic demand and to specify the GoS
30、(or performance) objectives. The results of these two tasks are input for dimensioning network resources and for establishing appropriate traffic controls. Finally, performance monitoring is required to check if the GoS objectives have been achieved and is used as a feedback for the overall process.
31、 E.490.1_F01Traffic controls DimensioningPerformance monitoringTraffic controls and dimensioningTraffic demand characterization Grade of service objectivesTrafficmodellingTrafficmeasurementQoSrequirementsTrafficforecastingEnd-to-endGoS objectivesAllocationto network componentsPerformancemeasurements
32、Figure 1/E.490.1 Traffic engineering tasks ITU-T Rec. E.490.1 (01/2003) 3 Clauses 6, 7, 8 and 9 describe each of the above four tasks. Each clause provides an overall view of the respective task and summarises the related Recommendations. Clause 10 summarizes a few additional Recommendations as thei
33、r scope does not match the items considered in the classification. 6 Traffic demand characterization Traffic characterization is done by means of models that approximate the statistical behaviour of network traffic in large population of users. Traffic models adopt simplifying assumptions concerning
34、 the complicated traffic processes. Using these models, traffic demand is characterized by a limited set of parameters (mean, variance, index of dispersion of counts, etc). Traffic modelling basically involves the identification of what simplifying assumptions can be made and what parameters are rel
35、evant from the viewpoint of the impact of traffic demand on network performance. Traffic measurements are conducted to validate these models, with modifications being made when needed. Nevertheless, as the models do not need to be modified often, the purpose of traffic measurements is usually to est
36、imate the values that the parameters defined in the traffic models take at each network segment during each time period. As a complement to traffic modelling and traffic measurements, traffic forecasting is also required given that, for planning and dimensioning purposes, it is not enough to charact
37、erize present traffic demand, but it is necessary to forecast traffic demands for the time period foreseen in the planning process. Thus the Recommendations cover these three aspects of traffic characterization: traffic modelling, traffic measurements and traffic forecasting. 6.1 Traffic modelling R
38、ecommendations on traffic modelling are listed in Table 1. There are no specific Recommendations on traffic modelling for the classical circuit-switched telephone network. The only service provided by this network is telephony given that other services, as fax, do not have a significant impact on th
39、e total traffic demand. Every call is based on a single 64 kbit/s point-to-point bidirectional symmetric connection. Traffic is characterized by call rate and mean holding time at each origin-destination pair. Poissonian call arrival process (for first-choice routes) and negative exponential distrib
40、ution of the call duration are the only assumptions needed. These assumptions are directly explained in the Recommendations on dimensioning. Table 1/E.490.1 Recommendations on traffic modelling Rec. No. Last issue date Title E.71110/92 User demand modelling E.712 10/92 User plane traffic modelling E
41、.713 10/92 Control plane traffic modelling E.716 10/96 User demand modelling in Broadband-ISDN E.760 03/00 Terminal mobility traffic modelling 4 ITU-T Rec. E.490.1 (01/2003) The problem is much more complex in N- and B-ISDN and in IP-based network. There are more variety of services, each with diffe
42、rent characteristics, different call patterns and different QoS requirements. ITU-T Recs E.711 and E.716 explain how a call, in N-ISDN and B-ISDN respectively, must be characterized by a set of connection characteristics (or call attributes) and by a call pattern. Examples of connection characterist
43、ics are the following: information transfer mode (circuit-switched or packet switched), communication configuration (point-to-point, multipoint, broadcast), transfers rate, symmetry (unidirectional, bidirectional symmetric or bidirectional asymmetric), QoS requirements, etc. The call pattern is defi
44、ned in terms of the sequence of events occurred along the call and of the times between these events. It is described by a set of traffic variables, which are expressed as statistical variables, that is, as moments or quantiles of distributions of random variables indicating number of events or time
45、s between events. The traffic variables can be classified into call-level (or connection-level) and packet-level (or transaction-level or, in ATM, cell-level) traffic variables. The call-level traffic variables are related to events occurring during the call set-up and release phases. Examples are t
46、he mean number of re-attempts in case of non-completion and mean call-holding time. The packet-level traffic variables are related to events occurring during the information transfer phase and describe the packet arrival process and the packet length. ITU-T Rec. E.716 describes a number of different
47、 approaches for defining packet-level traffic variables. Once each type of call has been modelled, the user demand is characterized, according to ITU-T Recs E.711 and E.716, by the arrival process of calls of each type. Based on the user demand characterization made in ITU-T Recs E.711 and E.716, IT
48、U-T Recs E.712 and E.713 explain how to model the traffic offered to a group of resources in the user plane and the control plane, respectively. Finally, ITU-T Rec. E.760 deals with the problem of traffic modelling in mobile networks where not only the traffic demand per user is random but also the
49、number of users being served at each moment by a base station or by a local exchange. The Recommendation provides methods to estimate traffic demand in the coverage area of each base station and mobility models to estimate handover and location updating rates. 6.2 Traffic measurements Recommendations on traffic measurements are listed in Table 2. As indicated in the table, many of them cover both traffic and performance measurements. These Recommendations can be classified into those on general and operational aspects (E.490, E.491, E.502 an
