ACC HDLC/LAP-B (ABM) User's Guide

Using HDLC/LAP-B (ABM) Protocol
Application Message Headers
Chapter 3 31
Application Message Headers
Normal HDLC/LAP-B (ABM) Mode
All application data is transmitted (or received) as the I-field of an
information frame. All headers and/or trailers are supplied by the
protocol for outgoing messages and removed by the protocol for incoming
messages. Only the I-field data to be transferred is dealt with by the
application program, which need not even be aware that HDLC/LAP-B
(ABM) is being used for the communications.