16.3 shows alternative hierarchical structuring of network is important. In these circumstances each manager has total jurisdic- management. In the centralised management structure of Figure tion over its own segment of the network, but maintains a monitor- 16.3(a) all management functions are carried out at one central ing brief over other segments. If one of the managers were to fail NETWORK MANAGER NETWORK NETWORK NETWORK MANAGER MANAGER Network Network Network Element Element NETWORK Element MANAGER SERVICE LEVEL MANAGER NETWORK NETWORK LEVEL MANAGER LEVEL MANAGER ELEMENT ELEMENT ELEMENT ELEMENT LEVEL LEVEL LEVEL LEVEL MANAGER MANAGER MANAGER MANAGER NETWORK NETWORK NETWORK NETWORK NETWORK NETWORK NETWORK NETWORK ELEMENT ELEMENT ELEMENT REMEMT EDMENT ELIGINT ELEMENT ELEMENT Figure 16.3 Network manager hierarchical structures: (a) centralised; (b) tree; (c) peer-to-peer Network management functions 16/5 then its neighbour steps in and assumes temporary responsibility on the card. Remote diagnostics is important so that the service over this additional part of the network. engineer is well prepared, often with spares, before he visits the site to fix the fault. The system should be able to issue work tickets, monitor the work being done on site, and keep track of all items 16.4 Network management functions returned for repair. Fault management involves much more than reacting to problems The prime function of a network manager is to ensure that the after they have occurred. The helpdesk should be in a position to network meets the aims of the organisation which it serves. This inform users of faults or potential faults, before they are affected by implies that the network will consist of a set of objectives against the fault and the complaints start to jam the helpdesk's telephones. which its performance can be measured and controlled. Unfortu- Configuration management provides a mechanism for managing nately these parameters are often not easy to define or to measure. the network elements, often called managed