session header (SH)

The Session Header (SH) is an initial label that is added during protocol handling when the session layer is traversed.

The Session Header follows the Presentation Header(PH), which is added to the payload data after the Application Header( AH).

As for the functionality of a Session Header, for example, in DQDB, the Session Header in the DQDB header is a 4-bytedata field that contains the data fields for the Virtual Channel Identifier( VCI), the Payload Type ( PT), the Segment Priority( SP), and the Checksum Field( HCS).