ACC HDLC-NRM (SDLC) User's Guide

Using HDLC-NRM (SDLC) Protocols
Application Message Headers
Chapter 3 31
Application Message Headers
The HDLC-NRM (SDLC) protocol does not use application message
headers. Both transmitted and received messages contain only the
information field of information frames sent across the link. The protocol
adds communications header and trailer to transmitted messages, and
removes the same from received messages.