udes the SNMP entity architecture having the SNMP engine that runs on the agent and the manager. 2. RFC 3412: Message processing and dispatching: There are multiple message processing models with regard to the SNMP versions. This RFC defines how the SNMP message corresponding to a particular version is dispatched for pro- cessing to the appropriate model. The SNMP engine defined in Version 3 can support multiple message processing models. For example, the SNMP manage- ment system can support SNMPvl, v2, and v3 protocols at the same time. The RFC also includes description of SNMPv3 Message Processing Model. 3. RFC 3413. SNMP Applications: This RFC describes five types of SNMP applications. 4. The five SNMP applications are: Command generators: An application that initiates an SNMP read or write request falls in this category. Command responders: An application that responds to SNMP read or write request falls in this category. Notification originators: An application that generates an SNMP notification falls in this category. Notification receivers: An application that receives the SNMP notifi- cation falls in this category. Proxy forwarders: An application that forwards SNMP messages falls in this category. 5. RFC 3414: User-Based Security Model (USM): This RFC handles mes- sage level security involving authentication and privacy implemented using USM. Along with authentication using security parameters in the SNMPv3 message, the privacy is obtained by encrypting the message at the sender and decrypting the message at the receiver. USM ensures that data security is achieved by: Preventing unauthorized access to data on transit from sender to receiver. Ensuring that the sender/receiver is valid and authorized to send/ receive a particular message. Ensuring that the message arrives in a timely manner and no re-order- ing is done by an unauthorized entity. Secret keys are used by the user for authentication and privacy. The authen- tication protocols suggested for use are MD5 (Message Digest 5) and SHA-1 (Secure Has