1、CCITT RECMN*M-3603 72 48b259L 0577305 473 m INTERNATIONAL TELECOMMUNICATION UNION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE MAINTENANCE: ISDN M.3603 (1 0/92) APPLICATION OF MAINTENANCE PRINCIPLES TO ISDN BASIC RATE ACCESS i Recommendation M.3603 CCITT RECMN*M-3603 92 E 4
2、862571 0577106 30T FOREWORD The CCITT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the International Telecommunication Union (ITU). CCIT is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view
3、 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 CCITT between Plenary Assemblies is cove
4、red by the procedure laid down in CCITT Resolution No. 2 (Melbourne, 1988). Recommendation M.3603 was revised by Study Group IV and was approved under the Resolution No. 2 procedure on the 5th of October 1992. CCIT NOTE In this Recommendation, the expression “Administration” is used for conciseness
5、to indicate both a telecommunication administration and a recognized private operating agency. O IT 1993 Ail 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 w
6、riting from the ITU. CCITT RECMN*Mm3b03 92 4Bb253L 0579107 24b Recommendation M.3603 APPLICATION OF MAINTENANCE PRINCIPLES TO ISDN BASIC RATE ACCESS (Melbourne 1988 as Rec. 1.603; revised and renumbered in 1992) Abstract This Recommendation defines capabilities and functions used by the network to m
7、aintain the physical layer Keywords - basic rate access; - ISDN; - maintenance. of ISDN basic rate access. 1 Scope of application This Recommendation covers the maintenance of that part of the ISDN subscriber basic access which is controlled by the network. The Recommendation follows the maintenance
8、 principles as defined in Recommen- dation M.20 i and applies to the basic access directly connected to the local exchange without any multiplexer or concentrator. The principle of controlled maintenance (as defined in Recommendation M.20 i) is applied for maintaining the subscriber basic access. Co
9、ntrolled maintenance is a method of sustaining a desied technical performance by the systematic application of supervision, testing and performance sampling in order to minimize preventive maintenance and to reduce corrective maintenance. 2 Network configuration for maintenance activities Figure 1N.
10、3603 is the basis for the general maintenance principles of the subscriber access. Subscriber !+I Subscriber access installation Configuration to be maintained 4 MSP Management Service Provider OAMC Operation Administration Maintenance Centre SAMF Subscriber Access Management Function SIMF Subscribe
11、r Installation Management Function For a detailed discussion of these terms, see Recornmendation M.3600 131. Note I - The subscriber access contains a digital section which can use different varieties of transmission techniques and may also include a regenerator. Note 2 - In some countries, certain
12、maintenance functions within the subscriber access are controlled by the subscriber installation (SIMF). FIGURE 1M.3603 Configuration for the maintenance of the basic rate access Recommendation M.3603 (10/92) 1 CCITT RECflN*N=3b03 92 I 4862591 0579108 182 I 3 Failure detection 3.1 General When the d
13、igital section (as seen by the exchange) of the ISDN subscriber basic access is in the active state, automatic supervision of the correct functioning of the layer 1 up to the NTl is operating. This supervision is called continuous automatic supervision on layer 1. When the ISDN subscriber basic acce
14、ss is in the active state (as seen by the exchange), automatic supervision of the correct functioning of the D-channel layers 2 and 3 is also operating. This supervision is called automatic supervision on layers 2 and 3 of the D-channel protocol. When the ISDN subscriber basic access is not in an ac
15、tive state (as seen by the exchange), the subscriber access may be periodically tested by the exchange. This is called the continuity test. 3.2 Automatic supervision 3.2.1 Continuous automatic supervision of layer 1 3.2.1.1 Objectives This supervision is realized by permanent automatic mechanisms lo
16、cated in the pieces of equipment of the subscriber basic access. These automatic mechanisms are continuously operational during the active period of the subscriber basic access. They are designed to detect malfunctioning of particular items, e.g. power supply, quality level of transmission, incoming
17、 signal, frame alignment. The continuous automatic supervision mechanism should be in operation even if there is no subscriber installation connected to the T reference point. For this, it must be possible for the digital section to be placed in a state where the automatic supervision can be perform
18、ed continuously although the T reference point may not be capable of full activation according to Recommendation 1.430 171. 3.2.1.2 Digital sectionfunctions Functions, which are allocated to the digital section are listed below: - - detection of loss of frame alignment within the digital system; det
19、ection of loss of frame alignment on the user-network interface as defined in Recommenda- tion 1.430 7; - supervision of the power feeding; - transmission performance monitoring. Note - In case the digital section has its own failure detection mechanism, failure indication signals may be sent to, an
20、d received by, the local exchange termination. Alternatively, the detection mechanisms are included in the exchange termination. 3.2.1.3 Transmission performance monitoring mechanisms Performance monitoring is provided in both directions of transmission. Specifically there will be error detection in
21、 each direction computed across the digital signal, for example, with a CRC or other error detection methods. Transmission errors detected at the LT are converted to Near-End Error (NEE) indications. Transmission errors detected at the NT are converted to Far-End Error (FEE) indications and sent bac
22、k to the LT. This enables performance for both directions to be assessed by the Administration. A function of the C-channel (see Recommendation G.960 6) may provide support of maintenance functions such as loopback activation and performance monitoring data gathering. 2 Recommendation M.3603 (10/92)
23、 CCITT RECflN*fl-3603 92 I ltb259L 0579109 O19 3.2.1.3.1 Performance monitoring capability (layer 1) It shall be possible to report the performance information from the exchange to the OAMC. It shall be possible to reset the parameter counts. Other issues under study include combining all links in s
24、ubscriber access; - - parameter consistence; - identifying maintenance phases affected by performance monitoring. 3.2.1.3.2 Required performance monitoring parameters und history The following principles apply to performance monitoring parameters and history: - parameters should be counted separatel
25、y in each direction when feasible to help isolate troubles and to better estimate network service provided to users; to support different maintenance uses, parameters should be counted for short durations (e.g. 15 minutes to one hour) and longer durations (e.g. 24 hours) as specified in Recommendati
26、on M.2110 5; a history of error counts should be stored to help deal with intermittent troubles; thresholding is covered in Recommendations M.34 2 and M.2110 5; performance information should be reported from the exchange to the OAMC - - - - - when thresholding crossing occurs; - on demand from the
27、OAMC. 3.2.1.4 Exchange termination functions Functions which are allocated to the exchange termination are listed below: - - transmission performance evaluation. supervision of information related to, or received from, the digital section; The transmission performance evaluation is based on a perman
28、ent processing of the elementary results presented by the continuous error monitoring of the digital section. The result of the processing will give information on at least one transmission quality level. Definition of quality levels and evaluation of timing conditions are outside the scope of this
29、Recom- mendation. 3.2.2 Automatic supervision of layers 2 and 3 of the D-channel protocol This activity covers supervision of activities of layers 2 and 3 of the D-channel protocol. Automatic super- vision on layers 2 and 3 will be made by self-acting mechanisms implemented in the network (e.g. in t
30、he ET). There are three categories of automatic supervision which may be performed by layers 2 and 3 of the D-channel protocols: - - - service provision incapability detection (e.g. incapability of layer 2 to establish a data link connection); protocol misoperation detection (e.g. at layer 2, detect
31、ion of dual TE1 assignment); error monitoring (e.g. the layer 2 CRC check procedure can detect the occurrence of an errored frame). These events should be recorded as discussed in Recommendation M.3640 4. Recommendation M.3603 (10192) 3 CCITT RECMN*M=3603 72 48b253L 0577110 830 3.3 Continuity test 3
32、.3.1 General When the subscriber basic access is not active (normal case and/or unknown fault condition case) or has not been recently activated, a continuity test may be applied in order to detect a possible fault condition. The test should be a simple goho go test. Note - The periodicity of testin
33、g on each access, if such test is performed on a periodical basis, shall be compatible with the failure detection time value (i.e. the time between failure occurrence and failure detection). 3.3.2 Control of the continuity test The continuity test is based on a normal activation of layer 1. If the a
34、ctivation is confmed by a positive result of the continuity test, the subscriber basic access is declared to be in good order for operation. No report is given to the OAMC. If the activation is not confirmed by a positive result of the continuity test, or if a failure is detected during the process,
35、 then the exchange will automatically enter into the failure localization process, and will report to OAMC. The result of the continuity test should be judged to be positive if the NT1 has the capability to signal that there is no failure on the subscriber basic access. 4 System protection When a fa
36、ilure is detected which has an adverse effect on the availability and/or functionality of network equipment, the access is considered “out of service due to failure“ and call attempts may be rejected to prevent further damage or to remove the adverse effect. In this condition, removal of power from
37、the line may be required. 5 Fault information A fault condition confirmed by the exchange and related to a subscriber basic access and/or subscriber installation shall be reported to the OAMC in a message. The message could be presented after an automatic identification of a faulty maintenance entit
38、y (ME) has been made (see Q 6). 6 Fault localization 6.1 Automatic confirmation of faults within the subscriber basic access An automatic test procedure to confm a detected possible fault condition within the subscriber basic access should be provided. It should be initiated by an automatic reaction
39、 of the exchange, following abnormal conditions which have been detected by the processes presented above, Le. continuous supervision, supervision on layer 2 and layer 3, continuity test. The process is based on loopback techniques which aliow the exchange to verify that there is no fault within the
40、 network and that the failure condition, if any, is not of a temporary nature. If faults are detected in the D-channel layers 2 and 3 communication, clear differentiation between faults within the subscriber installation and within the subscriber access should be possible. 4 Recommendation M.3603 (1
41、0/92) CCITT RECMN*M-3603 92 H 4862573 0577333 777 = !qrl - II I 6.2 Identijcation of the maintenance entity affected by a fault 6.2,l General Identification should be made on demand or automatically following the indication of fault conditions by the network or following a subscriber complaint. Befo
42、re undertaking the appropriate action, it is necessary to identify (Le. to know) the maintenance entity affected by the fault. 6.2.2 Objectives The main objective of this function, which is controlled by the SAMF is to indicate to the OAMC, if the fault is: - within the ET and/or the LT; - within th
43、e line and/or the NT1, the localization specified between NT1 or line if possible; - within the subscriber installation. 6.3 bopbacks 6.3.1 Locations of loopbacks within the subscriber basic access Loopback locations for fault localization and verification controlled by the local exchange are shown
44、in Figure 2M.3603. Note - Other loopbacks might be necessary. FIGURE 2/M.3603 Loopback locations within the subscriber basic rate access 6.3.2 Characteristics of loopbacks within the subscriber access The characteristics of loopbacks within the subscriber access are given in Table 1M.3603. Other loo
45、pbacks used in support of maintaining the subscriber installation from within the subscriber installation are specified in Recommendation M.3602 8. Recommendation M.3603 (10/92) 5 CCITT RECMN*M.3603 92 m gb2591 0579112 603 = looped back Loopback Location Loopback type Control point Implementation me
46、chanism TABLE 1N.3603 Characteristics of loopbacks within the subscriber basic rate access Complete loopback (2B + D at least) Complete loopback (2B + D at least) Complete, Under control Local Recommended transparent or of local maintenance non-transparent exchange (Note 1) Complete, Under control L
47、ayer 1 Optional transparent or of local non-transparent exchange (Note 1) 1 1A 21 In LT, as near as possible to the line, towards the ET In the regenerator In NT1, not impacting the network interface 2 I I In NT1, as near as possible to T reference point, towards ET (Note 2) 31 non-transparent (Note
48、 4) In NT2, as near as possible to T reference point, towards T (Note 5) exchange Partial, transparent or non-transparent I I l I Under control Layer 3 of local exchange Partial, transparent or non-transparent Under control Layer 3 of local exchange 2B+D 4 E Complete, Under control Layer 1 transpare
49、nt or of local In the TE or TA In ET, towards the line Partial, transparent or non-transparent Recommended Under control Layer 3 of local exchange Bi Bz (Note 3) Partial, transparent or non-transparent Under control Layer 3 of NT2 or TJ3TA Optional Bi B2 (Note 3) Optional Bi Bz (Note 3) Optional Bi B2 (Note 3) Optional Note 1 - Whether the loopback is transparent or non-transparent is for further study. Whether or not a transparent loopback is used, the loopback should not be affected by configurations and conditions beyond the point at which the loopback is provid
