section overhead (SOH)
The Section Overhead (SOH) is represented by the first nine bytes of each of the nine lines of a Synchronous Transfer Mode (STM) transmission frame in the first hierarchy level (STM-1) within the Synchronous Digital Hierarchy ( SDH).
The information contained therein ensures the transport of the SDH user data between two node computers of an SDH network. A distinction is made between the Regenerator Section Overhead ( RSOH) and the Multiplex Section Overhead ( MSOH), whereby an MSOH can be divided into several RSOHs.