Editing Synchronous optical networking (section)

====Transport overhead====
The transport overhead is used for signaling and measuring transmission [[bit error rate|error rates]], and is composed as follows:

:;Section overhead: Called regenerator section overhead (RSOH) in SDH terminology: 27 octets containing information about the frame structure required by the terminal equipment.
:;Line overhead: Called multiplex section overhead (MSOH) in SDH: 45 octets containing information about error correction and Automatic Protection Switching messages (e.g., alarms and maintenance messages) as may be required within the network. The error correction is included for STM-16 and above.<ref name="FECOptical"/>
:;Administrative unit (AU) pointer: Points to the location of the J1 byte in the payload (the first byte in the virtual container).<ref name="cisco-sdh"/>