d objects. Agent: It communicates with the managed objects to collect data. The infor- mation in MIT is queried by the agent and updated using commands like Get, Set, and SO on. It also has event detection and processing. CMISE (common management information service element): Has a set of operations providing communication. It works on CMIP protocol to achieve message exchange. ACSE (association control service element): Handles opening and closing of communication between the manager and the agent. There are three kinds of messaging that happens between the manager and the agent as shown in the message communication model (see Figure 5.8). They are: Request/operations: These are message queries sent by the manager to the agent requesting information. Responses: These are messages sent by the agent to the manager as response to a query from the manager. Notifications/traps: When an event occurs that needs to be notified to the manager, the agent generates a trap with data on the asynchronous event. Fundamentals of EMS, NMS and OSS/BSS Resquests/operations Manager Agent Responses Applications Managed objects Notifications/traps Figure 5.8 Message communication model. Manager Operations/requests/responses Agent applications traps/notifications applications Manager Agent communication SNMP (Internet) communication module CMIP (OSI) module Transport UDP/IP Transport layers OSI lower layer profiles layers Physical medium Figure 5.9 Communication transfer protocols. The transfer protocols in the OSI communication model is detailed with three lay- ers as shown in Figure 5.9 on communication transfer protocols. They are: Messaging between manager and agent application: The message communi- cation model already discussed describes the supporting messages. Application layer protocol: The application layer protocol for interaction between agent and manager module is SNMP for the Internet and CMIP for the OSI network. Transport layer: The model specifies the use of UDP/IP and OSI lower layer profiles. OSI Network Management 