ate module in the message processing subsystem. Security subsystem: It handles message level authentication and privacy. User- based security model (USM) is usually used when SNMPv3 module exist- ing in the message processing subsystem. When the messaging supported includes other versions of SNMP then community-based security model or other security model would also be supported in the security subsystem. Access control subsystem: Authorization of access to specific objects is han- dled in this component. View-based access control model (VACM) is sup- ported in the access control subsystem of SNMPv3. The components of the SNMP applications are: Command generator and command responder: The generator component performs the action of command generation and the responder will respond to commands. The generator is linked with commands like get, get-next, and get-bulk while the responder is linked with commands like get-response. The SNMP manager will contain a command generator and the SNMP agent contains the command responder. Notification receiver and notification originator: These components han- dle notifications like trap and inform. The SNMP manager usually con- tains a notification receiver and the SNMP agent contains the notification originator. Proxy forwarder: This component forwards the request without consideration on the object being handled. Other: The possibility of adding extensions in SNMP applications entity is accounted for using a component named Other. The Other Application box acts as a placeholder for applications that may be developed in the future. SNMPv3 message structure is shown below: Message Message Message Message Message Context Context Version Maximum Flags Security Security Engine Model Parameters The message version is used by the message processing unit to identify the SNMP version used in the request or response message. This ID is critical for the dispatcher in identifying the version of message. The message ID, message maximum size, message flags, and message security model is us