1、STD-ITU-T RECMN M-3385-ENGL 2000 48b257L Ob85732 085 INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU M.1385 (02/2000) SERIES M: TMN AND NETWORK MAINTENANCE: INTERNATIONAL TRANSMISSION SYSTEMS, TELEPHONE CIRCUITS, TELEGRAPHY, FACSIMILE AND LEASED CIRCUITS I
2、nternational data transmission systems Maintenance of international leased circuits that are supported by international data transmission systems ITU-T Recommendation M.1385 (Formerly CCITT Recommendation) STD.ITU-T REC“ M.L3 all users of this Recommendation are therefore encouraged to investigate t
3、he 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 G.701 (1 993), Vocabulary of digital transmission and multiplexing, and Pulse Code Modulation
4、(PCM) terms. ITU-T Recommendation M.60 (1993), Maintenance terminology and definitions. CCITT Recommendation M.80 (1 988), Control stations. CCITT Recommendation M.90 (1 988), Sub-control stations. CCITT Recommendation M. 1012 (1 988), Circuit control stations for leased and special circuits. CCITT
5、Recommendation M. 1 O1 3 (1 988), Sub-control station for leased and special circuits. ITU-T Recommendation M. 1045 (1 996), Preliminary exchange of information for the provision of international leased circuits and international data transmission systems. CCITT Recommendation M. 1060 (1 988), Maint
6、enance of international leased circuits. ITU-T Recommendation M. 1300 (1 997), Maintenance of International data transmission systems operating in the range 2.4 kbit/s to 140 Mits. ITU-T Recommendation M. 1340 (1 996), Performance objectives, allocations and limits for international data transmissio
7、n links and systems. ITU-T Recommendation M. 1370 (1 998), Bringing-into-service of international data transmission systems. ITU-T Recommendation M. 1375 (1 998), Maintenance of international data transmission systems. STDmITU-T RECMN M.1385-ENGL 2000 = 4862573 Ob85738 5T3 ITU-T Recommendation M. 13
8、 80 (2000), Bringing-into-service of international leased circuits that are supported by international data transmission systems. ITU-T Recommendation M. 1400 (1 997), Designations for international networks. CCITT Recommendation M. 1 5 1 O (1 992), Exchange of contact point information for the main
9、tenance of international services and the international network. ITU-T Recommendation M. 1530 (1999), Network maintenance informution. ITU-T Recommendation M. 1535 (1 996), Principles for maintenance information to be exchanged at customer contact point (MICC). ITU-T Recommendation M. 1 537 (1 997),
10、 Definition of maintenance information to be exchanged at customer contact point (MICC). ITU-T Recommendation M.1539 (1999), Management of the grade of network maintenance services at the maintenance service customer contact point (MSCC) . ITU-T Recommendation M. 1540 (1 994), Exchange of informatio
11、n for planned outages of transmission systems. CCITT Recommendation M. 1560 (1 992), Escalation procedure for international leased circuits. Terms and definitions ITU-T Recommendation M. 1300 9 provides general descriptions of international data transmission systems. Terminology and definitions rela
12、ting to this ITU-T Recommendation are provided in ITU-T Recommendations G.701 i and M.60 2. For the purposes of this ITU-T Recommendation, the following definitions of an international digital leased circuit and Service Level Agreement (SLA)/Contract apply: 3.1 An international digital leased circui
13、t: Is the digital path between two Network Terminating Equipments (NTEs). The digital leased circuit may be bidirectional or unidirectional and its end points are at the boundaries between the Network Operator/Service Provider and the Customer. The NTEs may be owned by the Network Operator/Service P
14、rovider or owned by the Customer. 3.2 An SLNContract: Is a set of appropriate procedures and targets formally or informally agreed between Network OperatodService Providers or between Network Operators/Service Providers and Customers, in order to achieve and maintain specified Quality of Service (Qo
15、S) in accordance with ITU (ITU-T and ITU-R Recommendations). The SLA may be an integral part of the Contract. These procedures and targets are related to specific circuitkervice availability, error performance, Ready for Service (RFS) date, Mean Time Between Failures (MTBF), Mean Time to Restore Ser
16、vice (MTRS), Mean Time to Repair (MTTR). 4 Abbreviations This Recommendation uses the following abbreviations: BIS Bringing-Into-Service CSES Consecutive Severely Errored Second ES Errored Second ISM In-service Monitoring MTBF Mean Time Between Failures STD-ITU-T RECMN M-IJ385-ENGL 2000 48b259IJ Ob8
17、5739 43T MTRS MTTR Mean Time To Repair NTE Network Terminating Equipment PCM Pulse Code Modulation PDH Plesiochronous Digital Hierarchy RFS Ready for Service SDH Synchronous Digital Hierarchy SEP Severely Errored Period SES Severely Errored Second SLA Service Level Agreement TMN Telecommunications M
18、anagement Network UTC Co-ordinated Universal Time Mean Time to Restore Service 5 Performance limits and objectives Performance limits should be consistent with those used during Bringing-Into-Service (see ITU-T Recommendation M. 1380 131). For short duration tests the limits given in clause 7/M. 134
19、0 1 O are appropriate. For all performance tests described in this ITU-T Recommendation, the Errored Second (ES) and Severely Errored Second (SES) limits should be met simultaneously for the test result to be considered acceptable. Network Operators/Service Providers should be aware that periods of
20、Consecutive Severely Errored Seconds (CSES), of between 3 and 9 seconds, called a “Severely Errored Period (SEP)“, can have a severe impact on some Customers leased circuit applications. CSESs are critical for some Customers leased circuit applications because they require the application to be rest
21、arted completely, since the installations own recovery system is no longer sufficient to cover the circuit interruption time. Performance limits and objectives for SEPS are for hrther study. 6 Maintenance records Network Operators/Service Providers should ensure that up-to-date information is held o
22、n file to assist maintenance activities. Clause 6/M. 1370 1 i and clause 6/M. 1380 131 provide details of information that should be available. In addition, a record should be kept of any particular maintenance agreement with the Customer, including for example SLA (Service Level Agreement). See als
23、o ITU-T Recommendations M.1510 15, M.1530 16, M.1535 17, M.1537 18 and M.1539 i91 for further information. Maintenance staff should refer to such agreements when dealing with a fault reported by the Customer. During maintenance operations, reference should be made to previous test results that are a
24、pplicable to the circuit under test. Original BIS test results should be available for all leased circuits. Network Operators/Service Providers should also keep a log of circuit interruptions, over an adequate period, with a view to meeting any claims from Customers. STD-ITU-T RECMN M-1385-ENGL 2000
25、 48b2591 Ob85740 151 = 7 Fault reporting procedures 7.1 Control and sub-control status A dual control or a control and sub-control relationship will have been agreed at the BIS stage. See clause 10M.1300 9, item ix) of clause 6N.1370 i i and 7.1h.1375 12. Where a control and sub-control relationship
26、 exists, responsibilities will be as described in ITU-T Recommendations M.80 3, M.90 4, M.1012 5 and M.1013 6. Where a dual control relationship has been established, Network Operators/Service Providers should have agreed an effective mechanism for coordinating maintenance activities. Under this arr
27、angement, to avoid confision, it is essential that the terminal stations inform each other of maintenance activities as rapidly as possible, in accordance with the performance agreed within the SLNContract, (see also ITU-T Recommendations M.1510 15, M.1530 16, M.1535 17, M.1537 is and M.1539 19). It
28、 is possible for a third-party centre to be designated as the control station. In this situation the leased circuit may not be routed via this centre, nor need this centre be situated in a terminal or transit country of the circuit. An example is when a “one-stop maintenance“ type arrangement is set
29、 UP. 7.2 In general, fault information relating to an international leased circuit can originate from a number of sources: - - Initial reception of a fault report a Customer (due to the failure or degraded performance of the circuit); the Network Operator providing the circuit (due to the failure or
30、 degraded performance of the network supporting the circuit); a connecting Network Operator providing part of the circuit (due to the failure or degraded performance of the network); a third-party centre, as described in 7.1 above. - - It is assumed that the Customer has carried out the following re
31、quisite checks to determine that the fault stems from the leased circuit for which the Network Operator/Service Provider is responsible: - results from the applications monitoring and control system; - information from the Network OperatodService Providers TMN system, if available. When fault inform
32、ation is received (especially a fault report from a Customer), the following information should be obtained: - - the Customer identifier; - - - - - name, title and contact details for the person reporting the fault; time of fault report, recorded in UTC; international designation of the faulty circu
33、it (see ITU-T Recommendation M. 1400 141); symptoms of the fault and if possible, the probable cause; the time the fault was first observed, recorded in UTC; any associated information that may assist with fault clearance. * Some Network OperatorService Providers have introduced computerized documen
34、tation and exchange of work orders and set up a Leased Circuits “help-desk“, which considerably facilitates operations. STD-ITU-T RECMN M*1385-ENGL 2000 48b259L Ob85741 098 The Customer should be given a fault reference, which can be used in future communications. They may also wish to know: - - - P
35、rior to undertaking corrective maintenance (for example loop-tests), the Customer must be asked to give permission for the circuit to be withdrawn from service. Following corrective maintenance, the Customer should be asked to confirm that their application is functioning correctly. where the fault
36、is located; the nature of the fault; above all, when the circuit will be restored, either by fault rectification or by restoration. 8 Fault localization It may be useful to reference Figure 1h4.1375 12 for guidance with fault localization. TMN data, which may be available at various locations within
37、 the Network Operator/Service Providers network, may be used to assist with fault localization. Initial localization should seek to establish whether a fault exists and to determine if it is located within the Customers premises, the national circuit portion or elsewhere. The use of the following in
38、formation may assist: - - network alarm information; - - whether the fault is intermittent or permanent; performance management information obtained fiom the network; results of the tests up to the Customer connection point, i.e. up to the point where the Network Operator/Service Provider is respons
39、ible. Where a fault is localized outside of the national circuit portion (i.e. within the international portion or distant national portion), it should be referred to a fault reporting point that has responsibility for international maintenance activities. This will typically be the fault reporting
40、point that has responsibility for the international data transmission system. When a fault is referred to another fault reporting point, the information given in 7.2 above should be exchanged. Further localization should seek to identifj the faulty element as quickly as possible. Where fault localiz
41、ation (or confirmation of it) is not achieved in a time consistent with the time to remove the fault or restore the circuit as specified in the SLNContract, Network Operators/Service Providers shall invoke the agreed escalation procedure (see ITU-T Recommendation M. 1560 21) to assist progress. 9 Ma
42、intenance tests For maintenance intervention tests, the circuit shall only be withdrawn from service with the Customers agreement, unless the circuit is completely interrupted. The use of In-service Monitoring (ISM) is thus highly advisable. Maintenance tests should be kept as short as possible to a
43、void significantly extending the out-of-service time. Customer service may be improved by using 24-hour “help desks and TMN facilities in order to schedule tests fiom a central location. Information about the fault condition detected, and the countermeasures planned, should be given promptly to the
44、Customer, in order to respect any contractual commitments. Any loopback facilities that may be available should be used when appropriate. Care must be taken to avoid the simultaneous operation of multiple loopbacks on a particular circuit. Once the need for a loopback no longer exists, then care sho
45、uld be taken to ensure that it is removed. STD-ITU-T RECMN M.L3BS-ENGL 2000 48b259L Ob85742 T24 W If both Network Operators have compatible equipment, then it may be possible to test the end-to-end continuity of a digital leased circuit. This may be possible using the TMN to apply a loopback conditi
46、on. However this type of testing requires the agreement of the Customer, since their circuit cannot be used at that time. Where an ISM capability is available for in-service observation of the circuit signal, then it should be used to assist maintenance operations. It should be noted that, for more
47、extensive measurements involving intrusive testing, the circuit will be interrupted. The duration of maintenance intervention tests will be dependent upon the nature of the fault report that has been received. 1) Where the circuit has a failure, a short test of basic integrity should be performed. S
48、ee clause 7M. 1340 1 O for suitable limits. 2) Where there has been an overall degradation of service, but that the circuit is not interrupted, a longer duration test will be appropriate. Network Operators/Service Providers should agree a suitable test date and time with the Customer. The Customer m
49、ay wish to retain access to the circuit until a more convenient time when a substantial out-of-service period may be more tolerable. When a 24-hour test is performed, Network Operators/Service Providers should use the same limits that were developed for initial BIS tests (see ITU-T Recommendation M. 1380 131). For a repetitive fault, or a fault requiring special investigation, a longer duration test, as described above, should be used. Reference can also be made to the fault history, performance informat
