Netscape NETSCAPE DIRECTORY SERVER 6.1 - ADMINISTRATOR, Administrator'S Manual

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About SNMP
Chapter 13 Monitoring Directory Server Using SNMP 421
• Managed Device-Initiated Communication
NMS-Initiated Communication
NMS-initiated communication is the most common type of communication
between an NMS and a managed device. In this type of communication, the NMS
either requests information from the managed device or changes the value of a
variable stored on the managed device.
These are the steps that make up an NMS-initiated SNMP session:
1.
The NMS determines which managed devices and objects need to be
monitored.
2.
The NMS sends a protocol data unit to the managed device’s subagent through
the master agent. This protocol data unit either requests information from the
managed device or tells the subagent to change the values for variables stored
on the managed device.
3.
The subagent for the managed device receives the protocol data unit from the
master agent.
4.
If the protocol data unit from the NMS is a request for information about
variables, the subagent gives information to the master agent and the master
agent sends it back to the NMS in the form of another protocol data unit. The
NMS then displays the information textually or graphically.
If the protocol data unit from the NMS requests that the subagent set variable
values, the subagent sets these values.
Managed Device-Initiated Communication
This type of communication occurs when the managed device needs to inform the
NMS of an event that has occurred. A managed device initiates communication
with an NMS to inform the NMS of a shut down or start up. Communication
initiated by a managed device is also known as a trap. Directory Server sends a trap
to the NMS whenever the Directory Server starts or stops.
These are the steps that make up a managed device-initiated SNMP session:
1.
An event occurs on the managed device.
2.
The subagent informs the master agent of the event.
3.
The master agent sends a PDU to the NMS to inform the NMS of the event.
4.
The NMS displays the information textually or graphically.