etail is just as applicable to LTEs and large cross-connects. Moreover, the formalism required to describe complete SDH networks was produced very much with this same functional decomposition in mind. We shall see later how these atomic functions can be paired between network ele- ments on opposite sides of a network to produce a complete traffic path that is sufficiently well defined for a computer to recognize. Chapter 10 Synchronous Optical Networks and Synchronous Digital Hierarchy Management of a service (e.g., 2-Mbit/s leased lines, Service Layer ISDN service) Management of paths across a complete network Network Layer requires an understanding of network topology Management of individual network elements (e.g., Element Layer multiplexers and cross- connects) Internal management of Fig. 10.22 Network management network elements Equipment Layer layering for the control of telecom networks and services. Control and Management Control and management within any type of telecommunications network (not just an SDH network) can best be viewed in terms of a series of layers (see Figure 10.22). At the lowest level, there is internal control of an individual network element, which performs internal housekeeping functions and deals in alarm and control primitives. ITU-T G.783 has rigorously defined a minimum set of control and alarm primitives for each of the SDH atomic functions, and these are the basis of all SDH management. However, beyond this, ITU-T TG.784 describes how such primitive information should be processed and ordered to produce derived information, such as error rates, which is stored in logs of defined dura- tion and reported at set intervals, and SO on. At the lowest level, some of this information might look rather different from that specified in G.783/4, and the like; however, the internal network element control system takes these and from them synthesizes the information that is required by the next level in the management hierarchy (i.e., the element manager). The element manager is a piece of 