G.709 header

The header of G.709 has some similarity to the headers of the Synchronous Digital Hierarchy( SDH) and Synchronous Optical Networks( SONET). It consists of the three data fields for the overhead, the payload and the forward error correction( FEC).

The overhead data field is 16 bytes long and supports operational, administrative, and maintenance functions, corresponding to the OAM functions for Operation, Administration, and Maintenance. The data field for the user data is 3,808 bytes long and is followed by the 256- byte data field for Forward Error Correction (FEC), which uses the Reed-Solomon code. At high data rates of 10 Gbit/s and above, Forward Error Correction provides additional coded data to ensure error detection and correction by the receiver.