HDLC High Level Data Link Control
HDLC is a Layer 2 protocol for point to point and multipoint delivery of data. The frame consists of flags to delimit the frame, along with addressing information and control information which is used when the protocol is employed in the acknowledged mode. Also included in the frame is a payload area and a CRC (Cyclic Redundancy Code). The protocol was originally developed by IBM variants include LAPB (Link Access Protocol Balanced) and LAPD (Link Access Protocol on the D Channel), as well as PPP (Point to Point Protocol).
