ess managed information. In Figure 21.12 this managed information is provided by an agent in the LAN hub. CMIP is part of the ITU-T X.700 OSI series of recommendations of the ITU. CMIP was developed and funded by government and corporations to replace and make up for the deficiencies of SNMP, thus improving the capabilities of network management systems. CMIP uses different terminology than SNMP. An agent maintains a management infor- mation tree (MIT) as a database; it models platforms and devices using managed objects (MOs). These may represent LANs, ports, and interfaces. CMIP is used by a platform to change, create, retrieve, or delete MOs in the MIT. It can invoke actions or receive event notifications. Object-oriented system concepts that are applied to the CMIP objects include contain- ment, inheritance, and allomorphism. Containment refers to the characteristic of objects being a repository of other objects and/or attributes. A high-level object for a commu- nication switch, for example, can contain several racks of equipment, each of which, in turn, can contain several slots for printed circuit boards. Here one might use the ITU-T M.3100 base class for a circuit pack to define the general features of modules within a communication switch. Object classes can then, in turn, be defined to represent the specific modules. Items including line interface cards, switching elements, and processors can be derived from the basic circuit pack definition. Each of these objects exhibits the behavior, actions, and attributes of both the derived classes and the base class. Allomor- phism is a concept coined by the CMIP standards bodies to refer to the ability to interact 21.7 NETWORK MANAGEMENT SYSTEMS IN ENTERPRISE NETWORKS CMIP: Create/Delete Get/Set/Action Management Information Tree Event-Report Ethernet-1 Token Ring Ethernet-1 Interface-1 Interface-1 Port-1 Port-1 Port-1 Agent Agent Agent Agent Figure 21.12 A typical overall architecture of an OSI network management system. (From Figure 2-12, page 48, Ref. 6.) with