Technical data

www.westermo.com Theoretical and general applications 139
SNMP software
Software used to communicate with the agent is called Network Management
Solution (NMS). The exchange of data with the agents is similar to communication
between a master and slaves, i.e. communication with the underlying devices takes
place through polling. The manager can request information from or perform an
action on the agent, this responds to the enquiries or actions requested. Another
option is for the agent to set a “trap” i.e. an event controlled function that is activated
by a predetermined condition. When this occurs the agent sends data back to the
manager.
Let us show an example:
In a large network there is critical equipment that uses UPS for its standby power. In
the event of a power failure, the UPS units are automatically connected and the
devices continue to work. This error condition must in some way be transferred to
the network administrator; this can be done through a trap detecting that the UPS
unit has been connected. The information is transferred to a SCADA system
(Supervisory Control And Data Acquisition) where the network administrator
receives an alarm, through a flashing icon (activated by the SNMP trap) on the UPS
unit.
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