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By far, the Simple Network Management Protocol (SNMP) has gained the most 
extensive application in the computer networks. SNMP has been put into use and 
widely accepted as an industry standard in practice. It is used for ensuring the 
transmission of the management information between any two nodes. In this way, 
network administrators can easily search and modify the information on any node 
on the network. In the meantime, they can locate faults promptly and implement 
the fault diagnosis, capacity planning and report generating. SNMP adopts the 
polling mechanism and provides the most basic function set. It is most applicable 
to the small-sized, fast-speed and low-cost environment. It only requires the 
unverified transport layer protocol UDP; and is thus widely supported by many 
other products.

In terms of structure, SNMP can be divided into two parts, namely, Network 
Management Station and Agent. Network Management Station is the workstation 
for running the client program. At present, the commonly used NM platforms 
include Sun NetManager and IBM NetView. Agent is the server software operated 
on network devices. Network Management Station can send GetRequest, 
GetNextRequest and SetRequest messages to the Agent. Upon receiving the 
requests from the Network Management Station, Agent will perform Read or 
Write operation according to the message types, generate and return the 
Response message to Network Management Station. On the other hand, Agent 
will send Trap message on its own initiative to the Network Management Station 
to report the events whenever the device encounters any abnormalities such as 
restart.

To uniquely identify the management variables of a device in SNMP messages, 
SNMP adopts the hierarchical naming scheme to identify the managed objects. It 
is like a tree. A tree node represents a managed object, as shown in the figure 
below. Thus the object can be identified with the unique path starting from the 
root.