ement standards are dependent on the principles of object modelling. The managed object forms an abstract repre- sentation of a resource looked at from the perspective of manage- ment. It may, for example, be a physical item, such as a multiplexer, AGENT or it may be logical, such as a connection. Managed objects contain attributes, each attribute having a value. Objects and their attributes are stored within what is known as a Management Information Base (MIB). The collection, or set, of managed objects which share identical MANAGED properties is referred to as a managed object class. Every occurrence OBJECTS of a managed object, which conforms to the same class, is called a managed object instance. Managed object classes are important since, if a management system knows the class of a managed object, then it knows unambiguously the management services which it can expect to be provided by the object. In OSI the Structure of Management Information (SMI) defines RESOURCES the modelling principle to be used for designing managed objects, along with the description associated with them. It provides sets of templates to describe the managed objects. Abstract Syntax Nota- tion One (ASN.1) is used for these, so that they are independent of MANAGED SYSTEM the architecture of the machine on which they run. An ASN.1 compiler would then take these ASN.1 object definitions and pro- vide the data structures and the source code routines needed to encode and decode management information relating to the man- Figure 16.12 Illustration of Manager and Agent process aged objects. 16/12 Network management OPERATIONS OPERATIONS AGENT MANAGER MANAGER NOTIFICATIONS NOTIFICATIONS MANAGED OBJECTS Figure 16.13 Alternative representation of a Manager and Agent process 1. Handles the representation of the resources being controlled in GET, which fetches the attribute values, from the MIB. the form of managed objects. SET, which replaces the attribute values specified by the new 2. Gives the manager a management view of the objects being v