The general plan for services in a synchronous network is that the synchronous transport provides circuits that are managed by the operator in a time scale down to hours or fractions of an hour (apart from protection and restoration, which are faster). These circuits may be used, for example, to carry public-switched traffic or as private circuits, or even both, such as in the North American SONET integrated digital loop carrier (IDLC) systems. Private circuits could be at multi-megabit rates, brought to the user via a local multiplexer.

The control of bandwidth on a time scale of seconds or less calls for other multiplexing technologies that have switching capability, such as ATM and IP. These typically employ SDH or SONET as their transport mechanism. SDH's unsuitability for independent fast switching applications is perhaps its only disadvantage.

As SDH is introduced more widely, the management capability of the network gradually increases because of the comprehensive monitoring and high-capacity management channels throughout the network. Operated in unison by a common network-management system, the DXCs, ADMs, and hub multiplexers allow centralized control of items (b) to (e) in Topic 4, while the integration of monitoring functions for all of the elements provides operators a complete view of their resources and their performances. Protection—item (a) in Topic 4—is best implemented locally for a speedy response.