Network Management

Network Management

Background

The Simple Network Management Protocol (SNMP) is an application-layer protocol that facilitates the exchange of management information between network devices. It is part of the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite. In any networking environment, if a fault develops and service is interrupted, users will expect the fault to be corrected and normal service to be resumed with a minimum of delay. This is 'fault management' (Bootman & Shabana, 1988: 163). Similarly, if the performance of the network - for example, its response time or throughput - start to deteriorate as a result of, say, increased levels of traffic in selected parts of the network, users will expect these to be identified and additional equipment / transmission-capacity to be introduced to alleviate the problem. This is an example of 'performance management'.

In addition, most of the protocols associated with the TCP/IP suite have associated operational parameters, such as the time-to-live parameter associated with the IP protocol and the retransmission timer associated with TCP. As a network expands, such parameters may need to be changed while the network is still operational. This type of operation is known as 'layer management'. Others include 'name management', 'security management', and 'accounting management'. SNMP enables network administrators to manage network performance, find and solve network problems, and plan for network growth (Boggs & Mogul, 1988: 222).

SNMP Basic Components

An SNMP managed network consists of three key components: managed elements, agents, and network-management systems (NMSs).

Examples of managed elements are: protocol, switch, router, workstation, and printer. Hardware managed elements are often referred to as managed devices. A managed device then is a network node that contains an SNMP agent and resides on a managed network. Managed devices collect and store management-related information and make this information available to NMSs using SNMP (Birkwood & Aidarous, 1988: 697).

The management-related information includes variables also known as 'managed objects' that can be either read or written to by the network manager via the network. It also includes, when appropriate, a set of 'fault reports' that are sent by a managed element when a related fault occurs. In the case of IP, for example, a read variable may related to, say, the number of IP datagrams / packets discarded when the time-to-live parameter expires, while a write variable may be the actual time-to-live timeout value (Bernstein & Yuhas, 1988: 784). Similarly, in the case of an exterior gateway, if a neighbour gateway ceases to respond to hello messages, in addition to modifying its routing table to reflect the loss of the link, the gateway may create and send a fault report - via the network - to alert the NMS to the problem. If the NMS receives a number of such reports from other neighbours, it can conclude that the gateway is probably faulty and that the problem is not just a communications line failure.

An agent is a network-management software module that resides in a managed device. An agent has local knowledge of management information and translates that information into ...