Simple Network Management Protocol

Simple Network Management Protocol (SNMP), simple protocol of network management in French, is a Communication protocol which makes it possible to the administrators network to manage the equipment of the network, to supervise and to diagnose problems networks, materials remote.

Principle of operation of protocol SNMP

The management system of network is based on three principal elements: a supervisor, nodes (or nodes) and agents. In terminology SNMP, the synonym to manage is more often employed than supervisory. The supervisor is the console which makes it possible the administrator network to carry out requests of management. The agents are entities which are on the level of each interface, connecting the managed equipment (node) to the network and making it possible to recover information on various objects.

Switchs, hubs, routers and waiters are examples of equipment containing of the manageables objects. These manageables objects can be material information, parameters of configuration, statistics of performance and other objects which are directly related to the behavior in the course of the equipment in question. These objects are classified in a basic kind of data arborescent called MIB (“ Management Information Base ”). SNMP allows the dialog between the supervisor and the agents in order to collect the objects desired in the MIB.

The architecture of management of the network proposed by protocol SNMP is thus founded on three principal elements:

the managed equipment (managed devices) is elements of the network (bridges, switches, hubs, routers or waiters), containing “objects of management” (managed objects) being able to be information on the material, of the elements of configuration or the statistical data;
agents, i.e. a business application of network residing in a peripheral and charged to transmit the local data of management with the peripheral to format SNMP;
systems of management of network (network management systems noted NMS), i.e. a console through which the administrators can carry out tasks of administration.

SNMP in practice

Concretely, within the framework of a network, SNMP is used:

to manage the equipment
to supervise the behavior of the equipment.

A request SNMP is a datagram UDP usually bound for port 161. The diagrams of safety depend on the versions of SNMP (v1, v2 or v3). In versions 1 and 2, a request SNMP contains a name called community , used like a password. There is a different name of community to obtain the rights in reading and to obtain the rights in writing. In many cases, the colossal gaps of safety which comprise versions 1 and 2 of SNMP limit the use of SNMP to the reading of information because the community circulates without coding with these two protocols. A great number of free software and owners use SNMP to question the equipment regularly and to produce graphs giving an account of the evolution of the networks or the computing systems (MRTG, Cacti, Nagios,…).

Protocol SNMP defines also a concept of trap . Once defined, if a certain event occurs, such as for example the going beyond of a threshold, the agent sends a package UDP to a waiter. This process of alarm is used whenever it is possible to define a threshold of alarm simply. In many cases, alas, an alarm network should be started only by correlating several events.

Other uses

Protocol SNMP can also be used in the industrial field. In this case, SNMP is used to transport information not relating to the data-processing network. SNMP transports industrial applicatives information then.

In this case, SNMP resembles a basic kind of data arborescent.

See too

ASN.1
AgentX

External bonds

protocol SNMP
original source of the article
course SNMP
Site in English on SNMP
SNMP4J - Free Open Source SNMP API for Java
Example of contents of MIB
Getif: free customer SNMP for Windows
RFC 1157 for a documentation detailed on protocol SNMP

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