The synchronous digital hierarchy standard

Describes the technological, regulatory and market forces which led to the creation of the new hierarchical standard and the network requirements which were placed upon it. It then describes the frame format of the basic interface signal showing the principles of multiplexing the tributary bit rates, the functions of the overheads and the method adopted to achieve higher transmission rates. The problem of the separation of standards issues from equipment (or implementation) issues is then explored with particular reference to the SDH in the context of managed transmission networks and the multi-vendor environment. The paper finally addresses the future standards work associated with the synchronous hierarchy