HDLC Commands & Responses
I - Information exchange user data
S - Supervisory
- RR ACK, ready to receive I
- RNR ACK, not ready to receive
- REJ NAK, go back N
- SREJ NAK selective reject
U - Unnumbered
- SNMR/ SNME set mode, 2 octet control
- SARM/ SARME set mode, 2 octet control
- SABM/SABE, SIM, DISC, UA, DM, RD, RIM, UI,UP, RSET, XID, TEST, FMR