Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 1767)

SNMP Introduction
Software Reference for x310 Series Switches
C613-50046-01 REV A AlliedWare Plus TM Operating System - Version 5.4.4C 67.9
SNMP Messages
The SNMP protocol is termed simple because it has only six operations, or messages—get,
get-next, get-response, set, and trap, and SNMPv2c also has the get-bulk-request
message. The replies from the managed device are processed by the NMS and generally
used to provide a graphical representation of the state of the network. The two major
SNMP operations available to a management station for interacting with a client are the
get and set operations. The SNMP set operator can lead to security breaches, since SNMP
is not inherently very secure. When forced to operate in either SNMPv1 or v2 mode, when
operating with older management stations for example, care must be taken in the choice
and safe-guarding of community names, which are effectively passwords for SNMP.
Polling versus Event Notification
SNMP employs a polling paradigm. A Network Management Station (NMS) polls the
managed device for information as and when it is required, by sending get-request, get-
next-request, and/or get-bulk-request PDUs to the managed device. The managed device
responds by returning the requested information in a get-response PDU. The NMS may
manipulate objects in the managed device by sending a set-request PDU to the managed
device.
The only time that a managed device initiates an exchange of information is in the special
case of a trap PDU. A managed device may generate a limited set of traps to notify the
NMS of critical events that may affect the ability of the NMS to communicate with the
managed device or other managed devices on the network, and therefore to “manage”
the network. Such events include the restarting or re-initialization of a device, a change in
the status of a network link (up or down), or an authentication failure.