The process of controlling a network so as to maximise its efficiency and productivity. ISO's model divides network management into five categories: fault management, accounting management, configuration management, security management and performance management.
Fault management is the process of identifying and locating faults in the network. This could include discovering the existence of the problem, identifying the source, and possibly repairing (or at least isolating the rest of the network from) the problem.
Configuration management is the process of identifying, tracking and modifying the setup of devices on the network. This category is extremely important for devices that come with numerous custom settings (e.g. routers and file servers).
Security management is the process of controlling (granting, limiting, restricting or denying) access to the network and resources thereon. This could include setting up and managing access lists in routers (creating "firewalls" to keep intruders out), creating and maintaining password access to critical network resources, identifying the points of entry used by intruders and closing them.
Performance Management is the process of measuring the performance of various network components. This also includes taking measures to optimise the network for maximum system performance (periodically measuring of the use of network resources).
["Network Management: A Practical Perspective", Allan Leinwand and Karen Fang].