ed by the message processing system to define unique properties of the message. This set of tags are specific to the SNMPv3 message structure and would not be required when working with other versions of SNMPv3. The message security parameters are used by the security subsystem. There is a separate tag to specify the security model that is USM for SNMPv3. The context engine ID, Context name, and PDUs are encapsulated to a col- lection set called scoped PDU. Next let us discuss the concept of "Context" in SNMPv3. A collection of objects is called an SNMP context. Each of these col- lections is accessible by an SNMP entity. A context can be a collection based on a network element, a logical element, multiple elements, or a subset element(s). Each context has a unique identifier called the contextName, which is unique within an SNMP entity. A contextEngineID represents an instance of a con- text within an administrative domain. Figures 14.6 and 14.7 shows sequence diagramon command and notification. Each SNMP entity and administrative domain can have multiple contexts, SO the combination of contextEngineID and contextName uniquely identifies a context within an administrative domain. Command generator or Message processing Security notification originator Dispatcher subsystem subsystem Send the PDU Prepare outgoing message Generate request message Send request Receive response Network Prepare data elements Process incoming message Process response PDU Figure 14.6 Sequence diagram for command generation/notification origination. Fundamentals of EMS, NMS and OSS/BSS Command responder or Message processing Security Dispatcher notification receiver subsystem subsystem Process the PDU Process incoming message Prepare data elements Register context engine ID Receive request Network Send response Generate response message Prepare response message Process response PDU Figure 14.7 Sequence diagram for command response/notification receive. 14.5 Conclusion SNMP basic framework is suited for small networks where most of the fu