The Simple Network Management Protocol (SNMP) is an application-layer protocol designed to facilitate the exchange of management information between network devices and management stations in a standard way. SNMP enables setting and retrieving configuration and status information on devices as well as trap-directed notification of events on a device.
The SNMP model consists of the SNMP manager (typically the NMS), the SNMP agent on the network element, and the management information base (MIB), which is the database of information used to manage the network element. The protocol exchange between the SNMP manager and the SNMP agent consists of requests made by the SNMP manager, the associated responses from the SNMP agent, and the asynchronous notifications or traps that the SNMP agent generates due to notable events occurring on the network element.
The following figure shows the interaction between the NMS and the network element using SNMP.
Information is stored as managed objects in MIBs, which are files that describe the managed objects in a structured representation. An object is one of a number of attributes of the managed device. Objects are organized into a tree structure, in which each object is a leaf node with its own unique object identifier (OID). With the OID, the SNMP manager can uniquely identify the managed object in its requests and in the responses and notifications from the SNMP agent.
Objects can be:
Scalar—defines a single object instance.
Tabular—defines multiple related object instances, such as in a table.