Advanced Techniques
Asynchronous Frame Format
- The ``asynchronous packet protocol'' spoken between the host and TNC is very simple, since its only function is to delimit frames. Each frame is both preceded and followed by a special FEND (Frame End) character, analogous to an HDLC flag
- If a FEND ever appears in the data, it is translated into the two byte sequence FESC TFEND (Frame Escape, Transposed Frame End). Likewise, if the FESC character ever appears in the user data, it is replaced with the two character sequence FESC TFESC (Frame Escape, Transposed Frame Escape).