ABSTRACT
An Asynchronous transfer mode (ATM) network can be regarded as semantically independent as well as time-independent. The semantic independency refers to the ATM network being independent of the telecommunication services it supports. The ATM layer provides a set of services to the ATM adaptation layer above it when requested through a set of protocols operating in the ATM layer. ATM networks have the feasibility of combining several virtual channels into one virtual path. Broadband integrated services of digital networks specification on ATM cell transmission corresponds a basic transport within synchronous optical network (SONET) and/or synchronous digital hierarchy. SONET defines synchronous multiplexing of lower level digital signals with simplified interfaces to digital switches, cross-connect, and add-drop multiplexers. SONET is structured to encapsulate the signals generated under existing standards for digital hierarchies in networks based on electrical interfaces. SONET equipment uses synchronous clocks for timing and built-in integrated timing supply to implement it.
