The System Management Agent supports SNMPv1, SNMPv2c and SNMPv3. The SNMPv1 and SNMPv2c authentication service is based on community strings defined on the management station. The SNMPv3 authentication service is based on users. Each request must contain either a community name or a user name depending upon the protocol being used.
The SNMPv3 authentication process implements the User-based Security Model (USM) to obtain a security name and security level from a user name. Similarly, both SNMPv1 and SNMPv2c determine the security level from the community string. The security name and security level are then used together with a context string, a group name and a view name to perform access control. Access control is done through the View-based Access Control Model, (VACM). This access control model is used after the authentication process. So, while USM is designed and used for authentication, VACM is designed and used for authorization.
For information about the supported versions of SNMP within the System Management Agent, see SNMP Versions.