ages the name of an object can be found by reference to certain attributes associated with that name, again in analogy with The functions required from a network management system have the yellow pages of telephone directories. Distributed facilities are been conveniently classified by ISO into five groups: fault manage- often used for name management in which each area is responsible ment; configuration management; performance management; se- for managing the names within its territory. This prevents the delays curity management; and accounting management. These can be involved in searching through vast lists and enables faster retrieval considered to occur at all the three hierarchical levels, illustrated in by use of an hierarchical naming structure. Figure 16.3(b), giving an overall functional structure of network management, as in Figure 16.4. The aim of performance management is to monitor and improve on the performance of the network. It gathers statistical information to enable both long term planning and prediction of short term trends. A large network would require many monitor points for collection of information and some method of local analysis and filtering to prevent the network and the user from being swamped with data. Performance monitoring requires the maintenance of logs of objects and states, so as to show trends, and the adjustment of MANAGEMENT network resources in response to trends. ACCOUNTING Security management includes the authentication and authorisa- MANAGEMENT tion of access to the network by users. Although shown as a separate SECURITY MANAGEMENT function, security management cuts across several other functional PERFORMANCE areas, for example the need to limit access to users for certain MANAGEMENT configuration management functions. Security management there- CONFIGURATION fore determines who may do what in controlling a network. It is FAULT MANAGEMENT usual to provide security access in a layered structure, the upper layers being able to perform all the functions available to the