This document describes the usage and communications protocol stack to be employed on the Section and Line Data Communications Channels (DCC) that are part of the SONET format. The intent is to provide a channel that meets currently defined needs and can also accept additional functions in the future. In addition@ the protocol is specified such that the data communications channel can function as an integral part of the Telecommunications Management Network (TMN) as specified in ANSI and ITU-T documents. The protocols required to support management in an OSI environment are specified in this standard; other (compatible) protocols for different applications@ e.g.@ Software Download@ should be defined in other standards.