1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (1 0/96) SERIES E: TELEPHONE NETWORK AND ISDN Quality of service, network management and traffic engineering - Traffic engineering - ISDN traffic engineering Traffic and congestion control requirements for SS
2、 No. 7 and IN-structured networks ITU-T Recommendation E.744 (Previously CCITT Recommendation) ITU-T E-SERIES RECOMMENDATIONS TELEPHONE NETWORK AND ISDN OPERATION, NUMBERING, ROUTING AND MOBILE SERVICES INTERNATIONAL OPERATION E.100-E.229 OPERATIONAL PROVISIONS RELATING TO CHARGING AND ACCOUNTING IN
3、 THE INTERNATIONAL TELEPHONE SERVICE TELEPHONY APPLICATIONS ISDN PROVISIONS CONCERNING USERS E.330-E.399 QUALITY OF SERVICE, NETWORK MANAGEMENT AND TRAFFIC ENGINEERING NETWORK MANAGEMENT E.400-E.489 International service statistics E.400-E.409 E.230-E.299 UTILIZATION OF THE INTERNATIONAL TELEPHONE N
4、ETWORK FOR NON- E. 300-E. 329 International network management E.410-E.419 Checking the quality of the international telephone service TRAFFIC ENGINEERING Measurement and recording of traffic Forecasting of traffic E.420-E.489 E.490-E.799 E.490-E.505 E. 506-E. 509 Determination of the number of circ
5、uits in manual operation Determination of the number of circuits in automatic and semi-automatic operation E.5 1 0-E. 51 9 E.520-E539 Grade of service E.540-E.599 Definitions E.600-E.699 ISDN traffic engineering E.7 Mobile network traffic engineering E. 750-E. 799 QUALITY OF TELECOMMUNICATION SERVIC
6、ES: CONCEPTS, MODELS, OBJECTIVES AND DEPENDABILITY PLANNING E. 800-E. 899 Terms and definitions related to the quality of telecommunication services Models for telecommunication services E.800-E.809 E. 8 1 O-E. 844 Objectives for quality of service and related concepts of telecommunication services
7、Use of quality of service objectives for planning of telecommunication networks Field data collection and evaluation on the performance of equipment, networks and services E. 845-E. 859 E.860-E.879 E.880-E.899 For fitrther detaiis, please refer to ITU-T List of Recommendations. - STD-ITU-T RECMN E-7
8、44-ENGL L97b D 4862571 Ob26314 724 ITU-T RECOMMENDATION E.744 TRAFFIC AND CONGESTION CONTROL REQUIREMENTS FOR SS NO. 7 AND IN-STRUCTURED NETWORKS Summary This Recommendation has four main purposes: 1) Provide guidelines for implementing standardized traffic and congestion control procedures in SS No
9、. 7 and IN-structured networks. 2) Provide general guidelines on requirements that should be placed on network elements so that networks can be made robust to unforeseen problems. 3) Provide general principles and guidelines on how network level and network element level control should be structured
10、 to maximize effectiveness and avoid network problems. 4) Provide high-level requirements for traffic and congestion controls for consideration in developing specific procedures in other ITU-T Recommendations. Requirements and implementation considerations are covered for MTP, SCCP and IN traffic an
11、d congestion control procedures, and requirements are provided for adequate overload controls in network elements. In addition, considerations for making networks robust against failure propagation are discussed. Source ITU-T Recommendation E.744 was prepared by ITU-T Study Group 2 (1993-1996) and w
12、as approved under the WTSC Resolution No. 1 procedure on the 8th of October 1996. 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
13、. The IT-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 years, establishes the topi
14、cs for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recornmendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). In some areas of information technology whic
15、h fall within ITU-Ts purview, the necessary standards are prepared on a collaborative 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. O ITU 1997 All rig
16、hts 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. 11 Recommendation E.744 (10/96) 1 2 4 5 5.1 5.2 6 6.1 6.2 6.3 7 7.1 7.2 8 9 9.1 9.2 9.3 9.4
17、 10 11 - STD-ITU-T RECMN E.744-ENGL L77b 48b257L Ob2b3Lb 7T7 CONTENTS Scope References Definitions Abbreviations . Introduction Purpose . Concept of robustness . Requirements for MTP and SCCP traffic and congestion control procedures . MTP signalling link flow control procedures . MTP signalling rou
18、te management procedures Requirements for TFP, TFR and TFA procedures 6.2.1 6.2.2 Requirements for congestion controls . SCCP management procedures Intelligent network traffic and congestion controls High-level requirements . Standardized controls . Requirements for adequate overload control Additio
19、nal considerations for network operations and administration . Requirements for screening messages Requirements for data administration . I. Pnnciples for component removal Testing requirements History Relationship with network management and test procedures 2 2 2 4 4 4 9 10 10 10 11 11 11 11 . Reco
20、mmendation E.744 (10/96) 111 STD-ITU-T RECMN E.744-ENGL L77b i.i8b2572 ObZb3LA 57T Recommendation E.744 TRAFFIC AND CONGESTION CONTROL REQUIREMENTS FOR SS NO. 7 AND (Geneva, 1996) IN-STRUCTURED NETWORKS 1 Scope This Recommendation covers requirements and implementation considerations for traffic and
21、 congestion control procedures in SS No. 7 and IN-structured networks. It addresses traffic and congestion control procedures defined in other ITU-T Recommendations, and it describes the requirements and considerations needed to ensure the defined procedures work properly when they are implemented i
22、n a network. 2 References The following 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 are valid. All Recommendations and other references are subject to re
23、vision; all users of 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 currently valid ITU-T Recommendations is regularly published. ITU-T Recommendation Q.703 (1 996), S
24、ignalling System No. 7 - Signalling link. ITU-T Recommendation Q.704 (1 996), Signalling System No. 7 - Signalling network functions and messages. ITU-T Recommendation Q.705 (1993), Signalling System No. 7 - Signalling network structure. ITU-T Recommendation Q.714 (1996) Signalling System No. 7 - Si
25、gnalling connection control part procedures. CCITT Recommendation 4.724 (1988), Specfieations of Signalling System No. 7 - Signalling procedures. ITU-T Recommendation 4.764 (1 993), Signalling System No. 7 - ISDN user part signalling procedures. ITU-T Recommendation Q. 12 14 (1 999, Distributed func
26、tional plane for intelligent network CS-I. E.4 1 O-Series Recommendations, International network management. ITU-T Recommendation E.4 12 (1996), Network management controls. ITU-T Recommendation E.743 (1 99.9, Trafic measurements for SS No. 7 dimensioning and planning. CCITT Recommendation ES02 (1 9
27、92), Trafic measurement requirements for digital telecommunication exchanges. Recommendation E.744 (10/96) 1 3 Definitions For the purposes of this Recommendation, the following definitions apply: 3.1 congestion control: The automatic action taken in a network to prevent or reduce the overload of on
28、e or more network elements. Congestion control action may be implemented in other network elements beyond those experiencing overload. 3.2 overload control: The blocking, diverting or postponing, by or within a network element, of a processing load greater than its capacity or than can be handled at
29、 the relevant Grade of Service (GOS) objective. 3.3 successful message: A message is considered to be successfully delivered if it is delivered, uncorrupted, to the appropriate destination within such a time that it does not cause malfunctioning of the application. 4 Abbreviations For the purposes o
30、f this Recommendation, the following abbreviations are used. GOS GTT IN ISDN ISUP MTP SCCP SIB SS No. 7 SSP STP TFA TFC TFP TFR TUP UPT Grade of Service Global Title Translation Intelligent Network Integrated Services Digital Network ISDN User Part Message Transfer Part Signalling Connection Control
31、 Part Status Indication Busy Signalling System No. 7 Service Switching Point Signalling Transfer Point Transfer-allowed (signal) Transfer-controlled (signal) Transfer-prohibited (signal) Transfer-restricted (signal) Telephone User Pari Universal Personal Telecommunication 5 Introduction 5.1 Purpose
32、A key objective in operating SS No. 7 and IN-structured networks is the maximization of the robustness of the network, that is, the ability of a network to withstand both traffic overloads and failures of network elements. While many steps can be taken to avoid the occurrence of these network stress
33、es, cases of overload or failure will nonetheless occur. During such stresses, the operation of the network should be maintained, and the level of completed traffic kept as high as possible until the stress can be relieved. I 2 Recommendation E.744 (10/96) STD-ITU-T RECMN E-744-ENGL L99b 48b2591 Ob2
34、b320 128 To achieve this goal, the network resources have to be managed in a coordinated way so as to avoid, for example, that situations of focused overload spread out to other parts of the signalling/IN network or that momentary inability to face excessive demand on the signalling network will neg
35、atively affect the IN-structured network or vice versa. The actions in the signalling/IN network are distinct from those of the circuit-switched network. Interaction between management action on signalling/IN and the circuit-switched network are for further study. This Recommendation is required bec
36、ause without properly-implemented traffic and congestion controls, the SS No. 7 and IN-structured networks may not provide sufficient protection to properly and efficiently handle the congestion and overloads that are likely to arise. Some of the characteristics motivating these controls are the fol
37、lowing: - It is difficult to prepare accurate traffic forecasts for the quantities of calls and of signalling messages. SS No. 7 networks are subject to short-term overloads that may not be addressed adequately using dimensioning and provisioning procedures only. The distributed nature of the SS No.
38、 7 and IN-structured networks, such that overloads in one location may be caused by excessive traffic offered at distant points, making single-node controls inadequate. If one service provider stimulates more traffic than can be carried, congestion could seriously affect the service provided to othe
39、r, unrelated calls being handled by different service providers. Service logic processors, having very short holding times, will be much more subject to peak loading, and will provide severely degraded performance even if overloaded by only a small proportion. - - - - This Recommendation has four ma
40、in purposes: One of the main purposes of this Recommendation is to provide guidelines and performance characterizations that should be useful in implementing standardized traffic and congestion control procedures in SS No. 7 and IN-structured networks. A number of different traffic and congestion co
41、ntrol procedures are provided in ITU-T Recommendations. These procedures generally leave key parameter values to be specified as part of the implementation. In this Recommendation information is provided as to how the different procedures perform as a function of the parameter value settings, and su
42、ggestions are made as to how the parameters should be chosen in different types of networks. A second purpose of this Recommendation is to provide general guidelines on requirements that should be placed on network elements so that networks can be made robust to unforeseen problems. In particular, t
43、he needs for overload control are addressed and considerations are made of how such controls must interrelate to network level congestion controls. Principles are provided regarding what network element capabilities should be present in order to avoid fault and congestion propagation problems and ot
44、her forms of network instability. The third purpose of this Recommendation is to provide general principles and guidelines regarding how network level and network element level control should be structured to maximize effectiveness and avoid network problems. An important consideration here is in re
45、gards to interconnecting different networks. Network level controls and network element level controls must work properly in each network as well as between networks. To keep the different systems and controls harmonized, some basic principles need to be followed. This allows for various vendor prod
46、ucts and network implementations to be interconnected with a high-level of confidence the traffic and congestion control procedures will work properly and no fault conditions will result in network instabilities. Recommendation E.744 (10/96) 3 STD-ITU-T RECMN E.744-ENGL L77b 48b257L Ob2b32L Ob4 The
47、fourth purpose of this Recommendation is to provide high-level requirements for traffic and congestion controls. Specific description and definition of the control mechanisms are covered by the Q and E.4 10-Series Recommendations. 5.2 Concept of robustness The robustness of SS No. 7 and IN-structure
48、d networks is the ability of those networks to ensure: o system sanity, i.e. to perform all critical functions necessary for the system and network to that traffic overload and failures are contained and will not propagate through the network; perform properly regardless of overload level; and o max
49、imization of successful traffic throughput under overload and failure conditions. When a system becomes overloaded, it must reduce traffic in some manner. Overload controls within a system are intended to protect the system without reliance on actions from any other network element. The other way to protect a system is to have congestion controls between network elements, where an overloaded element requests others to reduce their traffic load to it. In order to achieve network robustness, overload and congestion control techniques need to be considered for all network e
