Difference Between Highlevel Data Link Control (HDLC) and PointtoPoint Protocol (PPP) (original) (raw)

Difference Between High-level Data Link Control (HDLC) and Point-to-Point Protocol (PPP)

Last Updated : 3 Oct, 2025

The main difference between **High-level Data Link Control (HDLC) and **Point-to-Point Protocol (PPP) is that High-level Data Link Control is the bit-oriented protocol, on the other hand, Point-to-Point Protocol is the byte-oriented protocol. Another difference between HDLC and PPP is that HDLC is implemented by Point-to-point configuration and also multi-point configurations on the other hand PPP is implemented by Point-to-Point configuration only.

What is HDLC?

HDLC is a synchronous data link layer protocol designed for reliable point-to-point communication and multipoint communication. HDLC is a bit-oriented protocol means one bit is transferred at a time. It provides error detection, correction, flow control, and multiplexing capabilities. It is commonly used in WAN environments and leased lines.

Frame Format of HDLC

**Features of HDLC

**Error Detection and Correction: HDLC uses error detection and correction mechanisms such as CRCs and acknowledgments to ensure the integrity of the transmitted data.
**Full-Duplex Communication: HDLC supports full-duplex communication, which allows data to be transmitted in both directions simultaneously.
**Multiplexing: HDLC supports multiplexing, which enables multiple data streams to be transmitted over a single communication channel.
**Efficiency: HDLC uses efficient bandwidth utilization techniques, such as sliding windows, to optimize data transmission.

What is PPP?

PPP is a versatile data link layer protocol that can be used for both synchronous and asynchronous transmission over point-to-point links only. PPP is a byte-oriented protocol means one byte is transferred at a time. It offers features like error detection, correction, flow control, and negotiation of various options. PPP is widely used in dial-up connections, DSL, and other point-to-point links.

PPP Frame format

**Features of PPP

**Authentication: PPP includes authentication mechanisms such as Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP) to ensure secure communication.
**Error Detection and Correction: PPP uses error detection and correction mechanisms such as CRCs and acknowledgments to ensure the integrity of the transmitted data.
**Network Layer Protocol Independence: PPP is independent of the network layer protocol being used, making it compatible with various network protocols.
**Multilink Support: PPP supports multilink connections, which allow multiple physical connections to be combined to increase the data transmission rate.

**Similarities Between HDLC and PPP

Both are data link layer protocols used for data communication between network devices.
Both use error detection and correction mechanisms to ensure the integrity of the transmitted data.
Both support full-duplex communication.
Both are widely used in various communication systems and have been standardized by international organizations.
Both support bandwidth optimization techniques, such as sliding windows.

Parameters	HDLC	PPP
Basics	HDLC is an ISO-developed bit-oriented code-transparent synchronous data link layer protocol.	PPP is a data link layer communication protocol for establishing a direct link between two nodes.
Stands for	HDLC stands for High-level Data Link Control.	PPP stands for Point-to-Point Protocol.
Protocol type	HDLC is a bit-oriented protocol.	PPP is a byte-oriented protocol.
Configuration	HDLC is implemented by Point-to-point link configuration and also multi-point link configurations.	PPP is implemented by Point-to-Point configuration only.
Layer	HDLC works at layer 2 (Data Link Layer).	PPP works at layer 2 and layer 3 (Network Layer).
Dynamic Addressing	Dynamic addressing is not offered by HDLC.	While in this Dynamic addressing is offered.
Media Type	HDLC is used in synchronous media.	PPP is used in synchronous media as well as asynchronous media.
Error detection	HDLC does not offer error detection.	PPP provides the feature of error detection using FCS (Frame Check Sequence) while transmitting data.
Compatibility	HDLC is not compatible with non-Cisco devices.	PPP is compatible with non-Cisco devices.
Format	HDLC protocols have two types- ISO HDLC and CISCO HDLC.	PPP uses a defined format of HDLC.
Authentication	HDLC does not provide link authentication.	PPP provides link authentication using protocols like PAP (Password Authentication Protocol) and CHAP (Challenge Handshake Authentication Protocol).
Cost	HDLC is more costly comparatively.	PPP is comparatively less costly.
Link Quality	HDLC does not offer the quality checking of established links.	PPP offers the quality checking of the established links using LCP (Link Control Protocol).

Conclusion

HDLC and PPP are both protocols used for data communication, but they differ in several key aspects, including connection type, error detection and correction, authentication, network layer protocols, framing, and flexibility. While HDLC is still used in some applications, PPP is more widely used in modern networking technologies and is considered a more flexible and versatile protocol.