1、CCITT RECMN*M.ZO 92 4862593 0578680 871 INTERNATIONAL TELECOMMUNICATION UNION CCITT TH E INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE MAINTENANCE: INTRODUCTION AND GENERAL PRINCIPLES M.20 (1 0/92) MAINTENANCE PHILOSOPHY FOR TELECOMMUNICATION NETWORKS Recommendation M.20 CCITT RECMN*I
2、-20 92 E 4862593 0578b8L 708 H FOREWORD The CCIT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the International Telecommunication Union (IT). CCIT is responsible for studying technical, operating and tariff questions and issuing Recommendations on them w
3、ith a view to standardizing telecommunications on a worldwide basis. The Plenary Assembly of CCIT 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 CCIT between Plenary Assemblie
4、s is covered by the procedure laid down in CCITT Resolution No. 2 (Melbourne, 1988). Recommendation M.20 was revised by Study Group iV and was approved under the Resolution No. 2 procedure on the 5th of October 1992. CCIIT NOTES 1) telecommunication administration and a recognized private operating
5、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 1993 Ail rights reserved. No part of this publication may be reproduced or utilized in any form or by any m
6、eans, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. CCITT RECMN*N-20 92 4862591 0578682 644 Recommendation M.20 MAINTENANCE PHILOSOPHY FOR TELECOMMUNICATIONS NETWORK# (revised 1992) Abstract This Recommendation describes maintenance philo
7、sophy for telecommunications networks. It also defines Keywords - maintenance, - maintenance entity, - network. network maintenance phases, network supervision capabilities, and bringing into service requirements. 1 General 1.1 Maintenance involves the whole of operations required for setting up and
8、 maintaining, within prescribed limits, any element entering into the setting-up of a connection (see Recommendation In order to properly plan and program the maintenance operations required to establish and maintain an analogue, digital or mixed network, the following general strategy is recommende
9、d. 1.1.1 A maintenance organization should be established using the guiding principles set fortb in Recommendations M.70 li and M.710 12 for automatic circuits switched over analogue, digital and mixed networks. In addition, the concept of control and subcontrol stations found in Recommendations M.8
10、0 13 and M.90 141 for international circuits and transmission systems should be implemented. 1.1.2 The strategy should include the following maintenance operations considerations: a) It should consider the evolution of the network from the present hghly analogue environment to the future almost whol
11、ly digital environment. In doing this, it must consider the new services and functions offered by the networks (e.g. CCITT Signalling System No. 7 and ISDN) and the maintenance tools and capabilities becoming available (e.g. performance monitoring). It should employ an overall maintenance philosophy
12、 that uses the maintenance entity concept, failure classification and network supervision process specified in 4 3. It should provide for the maintenance of the network systems, equipment and circuits during the following activities: - - - It should support other maintenance activities (8 6) associa
13、ted with the administration of maintenance operations (e.g. data bases, spare parts, failure statistics, etc.) along with a detailed plan for preventive maintenance, where required, on the various telecommunication equipments (hardware and software). b) c) installation and acceptance testing (O 4);
14、bringing into service (8 4); keeping the network operational (O 5). d) The principles described in Recommendation M.21 151 should also be taken into account. 2, It is recognized that for some Administrations, bringing into service is not considered to be part of maintenance. Recommendation M.20 (101
15、92) 1 CCITT RECMN*M-ZIO 92 4862593 0578683 580 e) It should have as a major aim to minimize both the occurrence and the impact of failures and to ensure that in cause of faiiure: - - the right place with; - the right equipment; - the right information at; - - the right actions; and - the right notif
16、ication. the right personnel can be sent to; the right time to perform; 1.2 To apply this general strategy in a network, the following principles can be used: Preventive maintenance The maintenance carried out at predetermined intervals or according to prescribed criteria and intended to reduce the
17、probability of failure or the degradation of the functioning of an item. Corrective maintenance The maintenance carried out after fault recognition and intended to restore an item to a state in which it can perform a required function. Controlled maintenance A method of sustaining a desired technica
18、l performance by the systematic application of supervision, testing and performance sampling in order to minimize preventive maintenance and to reduce corrective maintenance. 1.3 In general for all three types of network (analogue, digital and mixed), the use of controlled maintenance principles is
19、recommended, i.e., the maintenance actions are determined on the basis of information generated in the maintained system or coming from auxiliary supervision systems. 1.4 The advantages of the controlled maintenance approach are that it directs future maintenance activity to those areas where a know
20、n improvement in service to the customer will be achieved. The monitoring techniques which are inherent in controlled maintenance provide data which simplify the identification of hidden faults by using statistical analysis. 1.5 The smaller the portion of the network which is affected by a failure,
21、the more difficult and/or less economic it may be to detect it using controlled maintenance techniques. In these cases corrective and/or preventive maintenance techniques may have to be employed. 1.6 existing equipment included in the network (see Recommendations M.710, M.715 to M.725). 1.7 In analo
22、gue and mixed networks a mixture of the above-mentioned principles are used, depending on the The maintenance philosophy and fundamental principles are closely linked to - availability performance; - network technical performance; - network economics. 2 Maintenance objectives 2.1 Purpose The main pu
23、rpose of a general maintenance philosophy for analogue, digital and mixed networks is to accomplish the aims defined in 8 1.1. 2 Recommendation M.20 (10192) CCITT RECNN*N*20 92 4862591 0578b84 417 In addition the foilowing objectives should be fulfilled: - for a defined level of service the total co
24、st should be kept to a minimum by the use of appropriate methods (e.g. centralized operation and maintenance); - the same maintenance philosophy should be applied to exchanges, transmission equipment, data equipment, subscriber terminals, etc., wherever possible. 2.2 Economics New technology provide
25、s new possibilities for low cost maintenance not only for individual exchanges, but for the whole network. The operation and maintenance functions in a network should be planned in such a way that the life cost will be a minimum. For a defined level of service the total cost consists of - investment
26、 cost; - operations cost; - maintenance cost; - cost for loss of traffic. 2.3 Transition from analogue to digital networks including ISDNs The basic philosophy, as described in this Recommendation, is valid in principle for analogue, mixed and digital networks. However, many digital network parts ar
27、e more suited to the implementation of controlled maintenance than are analogue network parts. Due to new technological developments, maintenance functions can be incorporated within digital equipment. Analogue equipment often requires additional external maintenance systems in order to permit contr
28、olled maintenance, e.g. ATME No. 2 (see Recommendation 0.22 i). 2.4 Centralized maintenance Operations The introduction of digital telecommunications equipment with enhanced maintenance operations functions, including the facility for remote reporting and control, provides new opportunities for cent
29、ralization. Sup- plement No. 6.2 2 provides a description of a centralized maintenance organization. There are many benefits that can be gained from centralization. These include the ability to - - be more flexible in the organization of maintenance operations and administration; utilize highly skil
30、led human resources more efficiently; - - improve maintenance effectiveness; utilize more effectively data and data bases; - decrease maintenance costs; - increase the availability of transmission and switching systems; - improve quality of service. Nute - By the use of remote terminals, an Administ
31、ration can choose how they allocate their technical staff between local and centralized locations. Because of these benefits, it is recommended that centralized maintenance and other operations capabilities be considered when specifying new telecommunications systems and equipment. The general princ
32、iples for setting-up, operating and maintaining a Telecommunication Management Network (TMN) to support centralized maintenance and other operations are given in Recommendation M.3010 16. Recommendation M.20 (10/92) 3 In addition, the introduction of open or standardized interfaces between Network E
33、lements (NEs) and Operations Systems (OS) via TMN, including interfaces between TMNs will allow for enhancing maintenance, operations and testing procedures. These new enhanced procedures will be based upon remote capabilites to perform the following: LT - - - - loopbacks; - access to performance an
34、d test data; - status change and control; - switchovers; - others. 3 Overall maintenance philosophy 3.1 Nenuork components for maintenance 3.1.1 Maintenance entity concepts In order to facilitate efficient maintenance, the telecommunication network (analogue and digital) is divided into parts called
35、 Maintenance Entities (MES), Maintenance Entity Assemblies (MEAs) and Maintenance Sub-Entities (MSEs). Examples of MES, MEAs and MSEs are given in Figures 1/M.20,2/M.20 and 3N.20. MEA Digital switch El Two-way generator rn ME Maintenance entity MSE Maintenance sub-entity ET Exchange terminal LT Line
36、 terminai DIG MUX Digital muldex MEA Maintenance entity assembly U FIGURE 1/M.20 Maintenance entity concept for digital transmission networks 4 Recommendation M.20 (10D2) CCITT RECMN*Nm20 92 = 4862591 0578b8b 27T m NT2 NT1 I LT ET T U I -i- i -1- I4 Digital line system 4 ME ME rw jA ME Under study L
37、A ME r,- CI w TO403700-93 L1 ME .A ME _ w- D MSE , MSE ET Exchange terminal LT Line terminai ME Maintenance entity Exchange - CTE - GTE - STE I NT Network terminal TA Terminal adaptor TE Terminal equipment - LT FIGURE 2/M.20 Maintenance entity concept for the ISDN subscriber nehvork b Analogue circu
38、it MEA I+ I TO403710-93 1 Analogue line system I CTE Channel translation equipment GTE Group translation equipment STE Supergroup translation equipment MEA Maintenance entity assembly MSE Maintenance sub entity ME Maintenance entity LT Line terminal FIGURE 3m.20 Maintenance entity concept for analog
39、ue networks Two-way repeater Ei Recommendation M.20 (10/92) 5 CCITT RECMN*!.20 92 = 48b259L 0578687 126 3.1.1.1 Definition of Maintenance Entity Maintenance entities are defined by the following requirements: - The different equipment of a telecommunications network constituting the MES are intercon
40、nected at consecutive and easily identifiable interface points.3) At these points the interface conditions defined for these equipment apply and they possess the means of detecting maintenance events and the means of restoration. If the telecommunication equipment supports bidirectional transmission
41、, it normally consists of telecommunications equipment transmitting in both directions and then both directions are considered part of the same ME. When a failure occurs within a network, it is desirable that the maintenance alarm indication appears at the failed maintenance entity. When this is not
42、 practical, the indication should appear at the closest possible entity. Maintenance alarm information indications in an entity should not cause related alarm information indications at other entities. In the event that such indications are permitted to occur, they should clearly indicate that the f
43、ailure has occurred upstream, and not in the other entities displaying the information. Meeting these four requirements ensures that the responsible maintenance personnel are called into action, and that usually no unnecessary maintenance activity is initiated elsewhere. In a digitai network, for ex
44、ample, easily identifiable points may be provided by digital dismbution frames. Even in a location where no digital distribution frame is provided, an equivalent point, where defined interface conditions apply, will normally be identifiable. The interface between the exchange terminals and the digit
45、al switch may be accessed on a virtual basis. 3.1.1.2 Maintenance Entity inteSuce An ME has to perform a determined function between telecommunication interfaces (see Figure 4m.20). The performance is checked by internal failure detection and conveyed to the maintenance interface either automaticall
46、y after a failure occurrence, or after a request for maintenance information. - - - Telecommunication Maintenance Telecommunication interfaces c entity interfaces - - - -L= Maintenance interface - - 7- - T Maintenance Request for information maintenance TO403720-93 FIGURE 4M.20 Maintenance entity in
47、terface In addition, other operations and administrative functions may be canied out by the maintenance interface. Several types of maintenance interfaces are described in Recommendation M.3010 16 which covers the TMN. 3, If an easily identifiable interface point is not available, the interface poin
48、t may be replaced by a point permitting sectionaiization with functions such as, e.g. loopingback or performance monitoring. 6 Recommendation M.20 (10/92) 3.1.1.3 Definition of Maintenance Entity Assembly A maintenance entity assembly (MEA) is defined by the following requirements: - - - - an MEA co
49、ntains a group of MES assembled for additional maintenance purposes; requirements that apply for MES apply as well for MEAs; an MEA may detect failures and maintenance event information which can not be detected by MES; an MEA may provide end-to-end maintenance alarm information which can not be provided by MES. End-to-end information may be collected by using additional supervision means. 3.1.1.4 Defintion of Maintenance Sub-Entity (MSE) A maintenance sub-entity is defined by the following principles: - the different parts of an MSE constituting the MES are interc
