 lower layers. Accounting management aids in the preparation of bills for net- Figure 16.4 Network management functional structure work users and for tracking their payment. It also helps in the sale of network resources. It is the set of facilities which enables charges to be determined for the use of the network resources and for costs Fault management involves the detection, diagnosis and correc- to be identified and allocated to each resource. This management tion of network faults. These faults may be transient or persistent. function depends on statistics provided by the objects on the net- The network management system should be able to zoom into the work. Once again there is interaction between the various functions, network so as to highlight the area where the fault has occurred, the for example accounting management and configuration manage- node containing the fault, the card within that node and the circuit ment. The lowest cost is often determined by the cheapest route or 16/6 Network management the cheapest time zone, both of which are controlled by configura- Questions like the level of network resilience also need to be tion management. answered. This functional level is more concerned with long term Accounting management is frequently considered to include in- trends than with short term variations. For example Figure 16.5 ventory management. This is the function which keeps track of the individual elements being managed on the network, their charac- teristics, asset values and ownership and contractual information. MAXIMUM CAPACITY Although, in Figure 16.4, the five functions of fault, configura- tion, performance, security and accounting management are shown spread across the three levels of element management, network management and service management, they tend to be more rele- vant at certain levels compared to others. The element level is CURRENT CAPACITY primarily concerned with day-to-day management of the network. It deals with faults as they occur and makes planned changes to the confi