ocess is referred to as the agent. In the two-tier organizational model, the elements in the network that are managed does the regular network operation they are expected to perform as well as the management of the element by having the agent as part of the element (see Figure 5.1). The management functions as the agent are limited to functions like data collection, editing of data, and sending of event notification from the element. The "manager" manages the managed objects in the network using data from the agents. It works aggregated information sent from multiple agents and performs the network level functions. The manager can: Send queries to the agent Receive response from the agent Send update and edit notifications to the agent Collect data from the agent (alarm notification, performance report, etc.) The management database (MDB) is used to store management information. The data collected from the agents by the manager is processed to generate consoli- dated network level reports on fault, configuration, performance, and other man- agement functions. These processed reports as well as raw reports from the agent can be stored in MDB. The MDB serves as an archive for historical information on the managed objects. Fundamentals of EMS, NMS and OSS/BSS Manager Agent/manager Management database Agent Agent Managed objects Unmanaged objects Figure 5.2 Three-tier organizational model. There are three relational models to be discussed under OSI organizational models. They are: Two-tier model Three-tier model MoM model The components, functions performed by the components and their relation- ship, have already been discussed for the two-tier model. The three-tier model is similar to the two-tier model except for the presence of an additional "agent/man- ager" with its own management database between the manager and the agent (see Figure 5.2). We will call this additional component the intermediate component to avoid confusion in the discussion below. The manager in the intermediate component performs the role of c