snmp相关组件的介绍

An SNMP-managed network consists of three key components:
    * Managed device = Slave device
    * Agent = software which runs on Slave device
    * Network management system (NMS) = software which runs on Master
   
A managed device is a network node that implements an SNMP interface that allows unidirectional (read-only) or bidirectional access to node-specific information. Managed devices exchange node-specific information with the NMSs. Sometimes called network elements, the managed devices can be any type of device, including, but not limited to, routers, access servers, switches, bridges, hubs, IP telephones, IP video cameras, computer hosts, and printers.

An agent is a network-management software module that resides on a managed device. An agent has local knowledge of management information and translates that information to or from an SNMP specific form.

A network management system (NMS) executes applications that monitor and control managed devices. NMSs provide the bulk of the processing and memory resources required for network management. One or more NMSs may exist on any managed network.

Community-Based Simple Network Management Protocol version 2, or SNMPv2c, is defined in RFC 1901–RFC 1908.
RFC 2576 defines two possible SNMPv1/v2c coexistence strategies:
proxy agents
bilingual network-management systems.