QTECH QSW-2800 Инструкция по настройке - Manual (Page 35)

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2.4 SNMP Configuration
2.4.1 Introduction to SNMP
SNMP (Simple Network Management Protocol) is a standard network management protocol
widely used in computer network management. SNMP is an evolving protocol. SNMP v1
[RFC1157] is the first version of SNMP which is adapted by vast numbers of manufacturers for
its simplicity and easy implementation; SNMP v2c is an enhanced version of SNMP v1, which
supports layered network management; SNMP v3 strengthens the security by adding USM
(User-based Security Mode) and VACM (View-based Access Control Model).
SNMP protocol provides a simple way of exchange network management information between
two points in the network. SNMP employs a polling mechanism of message query, and
transmits messages through UDP (a connectionless transport layer protocol). Therefore it is
well supported by the existing computer networks.
SNMP protocol employs a station-agent mode. There are two parts in this structure: NMS
(Network Management Station) and Agent. NMS is the workstation on which SNMP client
program is running. It is the core on the SNMP network management. Agent is the server
software runs on the devices which need to be managed. NMS manages all the managed
objects through Agents. The switch supports Agent function.
The communication between NMS and Agent functions in Client/Server mode by exchanging
standard messages. NMS sends request and the Agent responds. There are seven types of
SNMP message:
Get-Request
Get-Response
Get-Next-Request
Get-Bulk-Request
Set-Request
Trap
Inform-Request
NMS sends queries to the Agent with Get-Request, Get-Next-Request, Get-Bulk-Request and
Set-Request messages; and the Agent, upon receiving the requests, replies with Get-
Response message. On some special situations, like network device ports are on Up/Down
status or the network topology changes, Agents can send Trap messages to NMS to inform the
abnormal events. Besides, NMS can also be set to alert to some abnormal events by enabling
RMON function. When alert events are triggered, Agents will send Trap messages or log the
event according to the settings. Inform-Request is mainly used for inter-NMS communication in
the layered network management.
USM ensures the transfer security by well-designed encryption and authentication. USM
encrypts the messages according to the user typed password. This mechanism ensures that