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| 2.4 |  | Network Management Tools |
| 2.4.1 |  | Network management system frameworks |

Network management can range from a solitary network consultant monitoring network activity with a simple protocol analyzer, to the use of a distributed database with auto-polling of network devices. Network management could even include the use of high end workstations generating real time graphical views of network topology changes and traffic. In general, network management is a service that employs a variety of tools, applications, and devices to assist network managers in monitoring and maintaining networks.

Most network management architectures use the same basic structure and set of relationships. End stations, or managed devices, such as computer systems and other network devices, run software that enables them to send alerts when they recognize problems. An example would be when one or more user determined thresholds are exceeded.

Upon receiving these alerts, management entities are programmed to react by executing one action, or a group of actions. This would include operator notification, event logging, system shutdown, or automatic attempts at system repair.

Management entities can also poll end stations to check the values of certain variables. Polling can be automatic or user initiated, but agents in the managed devices respond to all polls. Agents are software modules that first compile information about the managed devices in which they reside, and then store this information in a management database. Finally agents provide information proactively or reactively to management entities within network management systems (NMSs) via a network management protocol. Well known network management protocols include the Simple Network Management Protocol (SNMP) and Common Management Information Protocol (CMIP). Management proxies are entities that provide management information on behalf of other entities. Figure depicts a common network management architecture.

The International Organization for Standardization (ISO) has contributed a great deal to network standardization. The organization's network management model is the primary means for understanding the major functions of NMSs. This model consists of five conceptual areas:

- Performance management – The goal is to measure and provide various aspects of network performance in order to maintain internetwork performance at an acceptable level. Examples of performance variables include network throughput, user response times, and line utilization.
- Configuration management – The goal is to monitor network and system configuration information so that the effects on network operation of various versions of hardware and software elements can be tracked and managed.
- Accounting management – The goal is to measure network-utilization parameters so that individual or group use of the network can be regulated appropriately. Such regulation minimizes network problems because network resources can be apportioned based on resource capacities, and maximizes the fairness of network access among users.
- Fault management – The goal is to detect, log, notify users of, and if possible, automatically fix network problems to keep the network running effectively. Because faults can cause downtime or unacceptable network degradation, fault management is perhaps the most widely implemented of the ISO network management elements.
- Security management – The goal is to control access to network resources to prevent the network from being sabotaged or unintentionally brought down, and to prevent sensitive information from being accessed by unauthorized users. A security management subsystem can monitor users logging on to a network resource and deny access to those who enter inappropriate access codes.