3Com 2928 User Guide - Page 143

InformRequest; it supports more data types such as Counter64; and it provides various error codes, thus being able to distinguish errors in more detail. z SNMPv3 offers an authentication that is implemented with a User-Based Security Model (USM). You can set the authentication and privacy functions. The former is used to authenticate the validity of the sending end of the authentication packets, preventing access of illegal users; the latter is used to encrypt packets between the NMS and agents, preventing the packets from being intercepted. USM ensures a more secure communication between SNMP NMS and SNMP agent by authentication with privacy. Successful interaction between NMS and agents requires consistency of SNMP versions configured on them. You can configure multiple SNMP versions for an agent to interact with different NMSs. MIB Overview MIB Any managed resource can be identified as an object, which is known as the managed object. Management Information Base (MIB) is a collection of all the managed objects. It defines the hierarchy of the objects and a set of characteristics associated with the managed objects, such as the object identifier (OID), access right and data type. Each agent has its own MIB. NMS can read or write the managed objects in the MIB. TheFigure 1-1Figure 1-1Figure 1-1 relationship between an NMS, agent and MIB is shown in Figure 1-1. Figure 1-1 Relationship between NMS, agent and MIB Subtree OID MIB stores data using a tree structure. A node of the tree is a managed object and can be uniquely identified by a path starting from the root node. As illustrated in Figure 1-2, the managed object A can be uniquely identified by a string of numbers {1.2.1.1.5}. This string of numbers is the OID of the managed object A. A subtree can be identified by the OID of the root node of the subtree. For example, the OID of the subtree with the root node being B is the OID of node B -- {1.2.1.1}. Figure 1-2 MIB tree 1 1 2 1 1B 5 6 A 2 2 1-2