Simple Network Management Protocol (SNMP) is a UDP-based
network protocol. It is used mostly in network management
systems to monitor network-attached devices for conditions
that warrant administrative attention. SNMP is a component
of the Internet Protocol Suite as defined by the Internet
Engineering Task Force (IETF). It consists of a set of
standards for network management, including an application
layer protocol, a database schema, and a set of data objects.
SNMP exposes management data in the form of variables on the
managed systems, which describe the system configuration.
These variables can then be queried (and sometimes set) by
SNMP is based on the manager/agent model consisting of an
SNMP manager, an SNMP agent, a database of management
information, managed SNMP devices and the network protocol.
The SNMP manager provides the interface between the human
network manager and the management system. The SNMP agent
provides the interface between the manager and the physical
device(s) being managed.
The SNMP manager and agent use an SNMP Management
Information Base (MIB) and a relatively small set of
commands to exchange information. The SNMP MIB is organized
in a tree structure with individual variables, such as
point status or description, being represented as leaves on
the branches. A long numeric tag or object identifier (OID)
is used to distinguish each variable uniquely in the MIB
and in SNMP messages.
SNMP uses five basic messages (GET, GET-NEXT, GET-RESPONSE,
SET, and TRAP) to communicate between the SNMP manager and
the SNMP agent. The GET and GET-NEXT messages allow the
manager to request information for a specific variable.
The agent, upon receiving a GET or GET-NEXT message, will
issue a GET-RESPONSE message to the SNMP manager with
either the information requested or an error indication as
to why the request cannot be processed. A SET message
allows the SNMP manager to request a change be made to the
value of a specific variable in the case of an alarm remote
that will operate a relay. The SNMP agent will then respond
with a GET-RESPONSE message indicating the change has been
made or an error indication as to why the change cannot be
made. The SNMP TRAP message allows the agent to
spontaneously inform the SNMP manager of an "important"
what'll happen if one isup link gone down?
to brief this question...isup link is active between two
nodes.if one goes down what are all the messages will be
transfered to active node(bit wise,MTP wise)?