 the business management layer. There is a separate chapter that details the functions handled in the network management layer and this chapter is more about giving the reader a good under- standing of a network management application and the usual modules required while implementing a network management system. 11.2 Network Management System The network management system as the name signifies is used to manage a network. It provides a holistic view of the entire network. The different activities performed in a typical NMS when it is started and before any maintenance command can be issued are: Discovery of elements in the network: This can happen in different ways. The user of an NMS application can use a menu in the application to spec- ify the elements that need to be managed as an IP address or a range of addresses like "X.X.X.100" to "X.X.X.201." The set of servers to be man- aged may also be taken from a domain server that has an IP address of all the elements in the network. Auto discovery is also a common feature in most NMS systems where the NMS automatically identifies all the elements in a particular network. Discovery of components that make up the element: Each network element will be made of hardware components that perform a specific functionality and needs to be discovered. For example a call agent will have a set of links and these will be plugged into link interface cards on the call agent. Fault What Is NMS? logs will be generated with information on the component associated to the fault condition. Download of fault data: This activity usually happens after the resource (ele- ment and its components) discovery, SO that the fault data can be associated to the element and its specific component. The discovered resources are rep- resented as a tree in most NMS applications and associating the logs to the specific resource helps in debugging at the resource level. Download of performance data: Unlike fault logs, which are usually send to the NMS as and when they occur, the performance data is usual