Overview

High-level Data Link Control (HDLC) is a bit-oriented link layer protocol. HDLC can transmit any types of bit stream transparently.

HDLC supports only point-to-point link and does not support point-to-multipoint link.

HDLC supports neither IP address negotiation nor authentication. It uses keepalives to check link status.

HDLC works only on synchronous interfaces or synchronous/asynchronous interfaces in synchronous mode. HDLC is supported by serial interfaces that operate in synchronous mode and POS interfaces.