High-level Data Link Control (HDLC) is a bit-oriented data link protocol.
The distinct feature of HDLC is that data need not be a character set and any bit flow can be transmitted transparently.
Bit flow: data is transmitted in bit flows.
Character set: data is transmitted in character sets.
Through the trunk technology, you can aggregate many physical interfaces into an aggregation group to balance received and sent data among these interfaces and to provide more highly-reliable connections.
Currently, for Huawei Datacom products, member interfaces of an IP-Trunk interface must be encapsulated with HDLC.
Compared with other data link layer protocols, HDLC has the following features:
Full-duplex communication, which can send data continuously without waiting for acknowledgment and has high data transmission efficiency.
All frames adopt the Circle Redundancy Check (CRC) that numbers information frames. In this way, the information frames can be prevented from being lost or received repeatedly; thus, the transmission reliability is improved.
Transmission control function is separated from process function. Therefore, HDLC has high flexibility and excellent control function.
HDLC does not depend on any character set and can transmit data transparently.
Zero-Bit Insertion, which is used to perform transparent transmission, is easy to be applied on hardware.
Reference
RFC1549--------PPP in HDLC Framing
