Microsoft SNMP Service (Snmp.exe)
The SNMP service receives the SNMP packets from the network, decodes
them, and then dispatches them to the appropriate SNMP subagents.
The SNMP service is also called the SNMP Master Agent or the SNMP
Extendible Agent. The service is also responsible for intercepting
events (traps) from the SNMP subagents and forwarding trap messages
to the appropriate management systems.
Also known as SNMP Extension Agents (such as Inetmib1.dll, Hostmib.dll,
Lmmib2.dll), subagents are dynamic-link libraries that export a
set of entry points. When an SNMP message is received, the SNMP
service decodes the content and passes it to the appropriate subagent
by calling one of these entry points. After it processes the message,
the subagent passes the information back to the SNMP service. In
turn, the service forms the data into an SNMP message and sends
it back to the management system. The SNMP service and all SNMP
subagents depend on the SNMP Utility API.
SNMP Utility API (Snmpapi.dll)
This API provides the functions required by both the agent and manager
for processing SNMP messages. The SNMP service uses this library
for memory management operations, address- decoding routines, Object
Identifier handling routines, and so forth. A set of routines is
also provided that helps the SNMP subagents handle and order the
SNMP objects. Although it is not necessary to use the Snmpapi.dll,
the development of additional SNMP subagents is greatly facilitated
by the framework defined by this tool.
WinSNMP API (Wsnmp32.dll) and Management API
These APIs are provided to facilitate the development of SNMP management
software applications. The WinSNMP API provides a set of functions
for encoding, decoding, sending, and receiving SNMP messages. The
Management API is a simple, limited API that is written on top of
the WinSNMP and SNMP Utility APIs. It provides a very basic set
of functions that can be used to quickly develop basic SNMP management
SNMP Trap Service (Snmptrap.exe)
The trap service is a separate SNMP component that allows management
software applications to receive trap messages sent by SNMP agents.
The service receives incoming trap messages from the network and
forwards them through the WinSNMP API (Wsnmp32.dll) to the appropriate
SNMP Manager Applications (Snmputil.exe)
This tool, which is provided on the Windows 2000 and XP operating
system CD, is meant to be used as an example of a management software
application that is built on top of the Management API. You can
develop applications by using either the Management API or the WinSNMP
API, or both. Alternatively, you can develop a management application
directly on top of the Microsoft Windows Sockets API and not use
either the Management API or the WinSNMP API. For more information
about developing an SNMP management application, see the Microsoft®
Windows® 2000 Platform SDK documentation.