Mạng và viễn thông P27

Telecommunications Management Network (TMN)The goalof the ‘telecommunications management network’o r ‘ T M Nis to provide for consistent and efficient management of complex telecommunications networks. The T M N model describes the basic operating and management functionswhich a network operator has to conduct and the standard interfaces to be used between network components and network managementsystems.
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Mạng và viễn thông P27Networks and Telecommunications: Design and Operation, Second Edition. Martin P. Clark Copyright © 1991, 1997 John Wiley & Sons Ltd ISBNs: 0-471-97346-7 (Hardback); 0-470-84158-3 (Electronic) PART 5 RUNNING A NETWORK Networks and Telecommunications: Design and Operation, Second Edition. Martin P. Clark Copyright © 1991, 1997 John Wiley & Sons Ltd ISBNs: 0-471-97346-7 (Hardback); 0-470-84158-3 (Electronic) 27 Telecommunications Management Network (TMN) The goalof the ‘telecommunications management network’o r ‘ T M Nis to provide for consistent and efficient management of complex telecommunications networks. The T M N model describes the basic operating and management functionswhich a network operator has to conduct and the standard interfaces to be used between network components and network managementsystems. Key elements of the T M N concept are the management model, the Q3-interface and the CMIP (commonmanagementinformationprotocol).We discuss them allinthis chapter, whichin parallel gives an insight into the problems of managing complex networks. At the end, we also briefly discuss the SNMP (simple network management protocol), which is used as analternative to CMIP in many corporate and Internet/router networks.27.1 THE PROBLEMS OF MANAGING NETWORKS Figure 27.1 illustrates a typical telecommunications network of today. It provides a valuable insight into the complexity of managing even relatively simple telecommunica- tions networks. The figure shows a simple data network composed of four different component types, buteachprovided by different manufacturers.Theyeachhave independent network management systems ( N M S ) . Each NMS is capable of monitoring and controlling every aspect its manufacturer’s network equipment, but is incapable of monitoring or controlling other manufacturers’ devices. The componenttypes shown are 0 data switches, managed by a ‘proprietary’ network management system, NMSl 0 SDH (synchronousdigitalhierarchy)transmissiontechnology(linkssome of the switches and is managed by NMS2) 0 TDM (time division multiplex) transmission technology (links some of the switches and is managed by NMS3) 477478 (TMN) NETWORK TELECOMMUNICATIONS MANAGEMENT 0 direct leaselines provide for remaining switch links. These are supplied by another, public telecommunications network operator, for which there is no management system available to our operator A simple line failure is illustrated in Figure 27.1. An SDH connection has failed. The result is a plethora of alarms generated by both NMSl andNMS2. The network status screens of both NMS are likely to light up like Christmas trees in all sorts of colours. The SDH network management system, NMS2, will pinpoint the root cause of the problem, probably with the appropriate link alarm indicated in red. Meanwhile, NMSl is also showing red alarms, because one the adjoining switches has a malfunctioning of port and the other adjoining switch is isolated.Otherswitchesmayreport ‘yellow alarms’ as connections to the isolated switch have been lost. The exact cause of the problem, however, will not be clear from the information that appears on NMS1. Un- fortunately, this is likely to lead to a certain amountof confusion and wasted effort.. . . . .The human operator managing the SDH network naturally starts about his repair. . .meanwhile. . . . ..His colleague, the switch network manager watching the screen of NMSl is unaware of the root cause. Instead he addresses what appears to him to be the urgent problem of the isolated switch. Perhaps there has been a power failure? Maybe the switch needs to be restarted?.. .He calls his colleagueat the isolatedswitch site. Having done so, he is able to rule out a local cause. next he calls his SDH colleague and, of So course, discovers the most likely cause of his own alarms. He hands over responsibility and starts to get on with something else. But, you might ask, why did the switch manager not call the SDH manager to start with? The answer is that he is unable to determine easily the single cause of a lot of alarms. He must therefore address each alarm in turn, diagnosing the most critical alarms first. Considerable effort may go into checking each alarm and concluding a single root cause. Only afterwards can the human network manager truly rest in peacehis SDH as Q alarm $( line failure Figure 27.1 A typical telecommunications networkNETWORK PROVISIONING 479 Figure 27.2 Recognizingthatanetwork ...