3Com 10014299 manual Snmp architecture, SNMP-supported MIB

SNMP Overview 75

sub-tree, the network administrator can access the device with read or write authority. Otherwise, the operations will be rejected.

SNMP architecture

An SNMP entity comprises one SNMP engine and multiple SNMP applications. The SNMP engine is the core of the SNMP entity. It transceives and authenticates SNMP messages, extracts PDU (Protocol Data Unit), reassembles messages, and communicates with the SNMP applications. SNMP applications process PDUs, implement protocol operations, and stores/gets MIB.

The SNMP engine comprises the scheduler, message processing sub-system, security sub-system, and access control sub-system. SNMP applications include the command generator, command responder, indication generator, indication receiver, and proxy transponder. The SNMP entity that owns the command generator or indication receiver is called the SNMP manager, and the SNMP entity that owns the command responder, indication generator or proxy transponder is called the SNMP agent. Nevertheless, an SNMP entity can have functions of both manager and agent.

SNMP-supported MIB

To uniquely identify the equipment management variables in SNMP packets, SNMP identifies the managed objects by using the hierarchical structure to name them. The hierarchical structure is like a tree, in which, the nodes of the tree represent the managed objects. As shown in the following figure, it can use a path starting from the root to identify an object unambiguously.

Figure 35 MIB tree structure
1
1		2
	1	2
1	B	2
5	6
A

As shown in the above figure, the managed object B can be uniquely specified by a digit string {1.2.1.1}, which is the object identifier of the managed object. Consisting of collections of standard variable definitions of monitored network equipment, MIB describes the hierarchical structure of the tree

SNMP agents in the 3Com Router series support standard network management versions SNMPv1, SNMPv2c, and SNMPv3. MIBs that are compatible with the agents are shown in the following table.