tailieunhanh - Mạng và viễn thông P36

Maintaining the Network into the design of a network, and no matter how reliable the individual components are, corrective action will always be required in some form or another, to prevent or make good network and component failures, and maintain overall service standards. However, attitudes towards maintenance and the organization behind it vary widely, ranging from the ‘let it fail then fix it’ school of thought right through to ‘prevent faults at any cost’ | 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 36 Maintaining the Network No matter how much careful planning goes into the design of a network and no matter how reliable the individual components are corrective action will always be required in some form or another to prevent or make good network and component failures and maintain overall service standards. However attitudes towards maintenance and the organization behind it vary widely ranging from the let it fail then fix it school of thought right through to prevent faults at any cost . This chapter describes a typical maintenance regime in its philosophical organizational and procedural aspects. THE OBJECTIVES OF GENERAL MAINTENANCE As succinctly stated by ITU-T the objective of a general maintenance organization is to minimize the occurrence of failures and to ensure that in case of failure the right personnel can be sent to the right place with the right equipment at the right time to perform the right corrective actions. MAINTENANCE PHILOSOPHY In pursuing these objectives the wise network operator establishes a maintenance philosophy closely linked with overall targets for network quality and for the 663 664 MAINTAINING THE NETWORK proportion of time that the network is intended to be fault-free available . In this task he will take due account of network economics and the most likely causes of failure. Networks fail for all sorts of reasons common examples are cable or connector damage or disturbance equipment overheating electronic component failure mechanical equipment jamming or other failure mechanical wear dirty high resistance relay or switch contacts a diminishing problem as electromechanical exchanges are withdrawn power supply loss vandalism . to public payphones software errors erroneous exchange data poor connections between cables or other components