HDLC vs SDLC: Difference and Comparison

A communication protocol is a rule system that allows entities of the communication system for information transmission. The protocol defines the synchronization of communication, rules, and syntax.

HDLC and SDLC are two of the protocols that provide interconnection of point to multipoint between computers. They both are communication protocols used at the layer of a data link of computer networks.

Key Takeaways

  1. High-Level Data Link Control (HDLC) is a synchronous data link layer protocol, while Synchronous Data Link Control (SDLC) is IBM’s proprietary version of HDLC.
  2. HDLC is more versatile and widely implemented across different network types, while SDLC is mainly used in IBM’s Systems Network Architecture (SNA).
  3. Both protocols use bit-stuffing and cyclic redundancy checks (CRC) for error detection, but HDLC supports a broader range of network configurations.


The difference between HDL C and SDLC is the transfer modes. HDLC supports three transfer modes with NRM, whereas SDLC supports only one transfer mode, namely NRM. HDLC was developed by ISO (International Organization for Standardization), whereas SDLC was developed by IBM (International Business Machines Corporation).  


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The abbreviation for high-level data link control is HDLC. It was developed by ISO or simply an international organization for standardization. It provides both connectionless services and connection-oriented.

It is a concept that applies to a range of software and hardware configuration. As a system, it can be composed of software, hardware only, or a combination of both. 

Comparison Table

Parameters of ComparisonHDLCSDLC
InterpretationIt is a group of rules or protocols for data transmission between network points.It refers to a methodology in which the process of creating high-quality software is clearly defined.
DeveloperISO (International Organization for Standardization) IBM (International Business Machines Corporation)
DevelopedIn 2002In 1975
StandardISO/IEC 13239ISO/IEC 12207
Packet sizes Multiples of bit octets8, 16, 32, and so forth

What is HDLC? 

HDLC, or high-level data link control, is a group of rules or protocols for data transmission between network points. It is a bit-oriented protocol of an asynchronous data link layer.

The data in HDLC is organized into a unit or frame and across a network sent to a destination that verifies its arrival successfully. It also manages the pacing or flow at which data is sent. In the IP or Internet protocols, HDLC is used most frequently. 

HDLC is based on the SDLC protocol of IBM. The use of HDLC in the networking industry is to derive many other standards which are used today.

HDLC frames provide receivers to use algorithms for the detection of errors that might be created during transmission. As a standard protocol, it is used by several hardware makers. 

What is SDLC? 

The SDLC, or software development life cycle, is a framework that is used in project management. It describes the tasks and stages involved in deploying the instructions and each step of writing and data computers to execute specific tasks.  

An important goal is to efficiently and quickly produce high-quality software in steps or series of phases. The number of steps in this protocol will vary depending on the software of the business and business product goals.

When it comes to releasing, it is maintained until the software gets discontinued. Generally, there are steps between five and seven- although there are chances of more. 

For a given application, regardless of the kind of SDLC model, the documentation is crucial and done in parallel with the process of development. 

Main Differences Between HDLC and SDLC  

  1. HDLC has an option for the checksum of 32-bit but does not support the configurations of Loop or Hub go-ahead. On the flip side, SDLC supports Loop or Hub go-ahead configurations.  
  2. HDLC is considered a superset of SDLC because SDLC was submitted to various standards committees by IBM, and one of the committees, namely, ISO-modified SDLC, led to the creation of the HDLC protocol.  
Difference Between HDLC and SDLC
  1. https://www.sciencedirect.com/science/article/pii/0376507578900193
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