SNMP Manager Programmer's Guide

Introduction to Manager Services
SNMP Manager Programmer’s Guide–134249
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Extended Roles
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MIB object handling logic resolves user input regarding specific resources into
MIB object representations that describe the resources, in preparation for formatting
objects as variable bindings. This logic also converts SNMP object representations
into formats useful for analysis or output.
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SNMP packet construction logic converts user requests into Get, GetNext, or Set
packets and, when required, creates Trap packets. Packet construction consists of
initializing a packet structure and assigning to it values for all the variables that
SNMP requires, including variable bindings. SNMP packet interpretation logic
parses received packets to extract appropriate information.
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SNMP packet encoding logic converts a packet into a format that can be
transported to and understood by the target agent. SNMP packet decoding logic
converts a received packet into a structure your manager can work with.
All agents are able to interpret information encoded using the basic encoding rules
(BER) associated with ASN.1, which define how to encode an ASN.1 value as an
octet string. BER-encoded packets can be transmitted over any transport protocol
that the manager and target agent mutually support. NonStop agents can process
BER-encoded packets, but can also process packets encoded using the Tandem IPC
format, which provides the best encoding/decoding performance on NonStop Kernel
systems. Manager Services lets you encode and decode packets using either BER or
IPC format.
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SNMP packet transmission and receipt logic sends an encoded request packet to
an agent and receives a response packet; it also receives trap packets from an agent
or from a manager. When handling BER-encoded packets, you use the
programmatic conventions of a transport protocol by which the agent can be
addressed; most agents, including NonStop agents, support TCP/IP, although some
may be addressable using other transport protocols. When handling IPC-encoded
packets, you use file system procedure calls to communicate with local NonStop
agents or with NonStop agents on remote nodes addressable over an Expand line.
Extended Roles
In a large network, SNMP resource management may be most efficiently handled by
distributing manager activities among a hierarchy of managers, as Figure 1-4
depicts.
In this situation, a collection of resources, under the control of several subagents, is
monitored and controlled by several middle managers. When events of significance
occur, relating either to managed resources or to the middle manager itself, each middle
Figure 1-4. SNMP Manager Hierarchy
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Subagents
NonStop
Agent
Upper
Manager
Middle
Managers