col (TOP). For network management the key activities are involve at least four components: those within CCITT Study Group IV on the Telecommunications Management Network (TMN); within CCITT Study Group XV on 1. The communications path between the systems. the management of the synchronous digital hierarchy (SHD); and 2. The systematic delivery of the data along this path, which within CCITT Study Groups XI and XVII on ISDN management. requires a structured exchange of information. ANSI subcommittees TIMI and T1X1 are also developing stand- 3. A common language (the syntax) which is understood by all ards for management in fibre optic based systems (Sonet). parties involved in the data interchange. Other special interest groups (see Chapter 22) are the OSI Im- 4. The same conceptual interpretation of the data on all sides, i.e. plementors Workshop (OIW), mainly with participants from North the semantics. America, the European Workshop for OSI Standardisation (EWOS) and the Asia and Oceania Workshop for OSI Standardisation OSI has divided these requirements into a hierarchical structure (AOWS). Many of these profiles, and others developed by various within its reference model. The basic concept is that the functions OSI Workshops, are submitted to JTC1 in order to have them involved in any communications can be divided into seven separate incorporated as International Standardised Profiles (ISPs). and well defined layers. Communications between layers within Another area, as important as the standards, is that of conformance different systems is defined by service primitives. OSI standards testing. Items which pass these tests can then be certified, so that the define the services each layer provides, and service definitions are user knows that two such items within his network will interwork then the basis for the protocol defining how layers in one system with each other. Conformance test specifications have been de- communicate with layers at the same level within another system. veloped by various interest grou