Editing High-Level Data Link Control (section)

{{Short description|Communications protocol}}
{{original research|date=March 2019}}
{{Infobox networking protocol
| title        = High-Level Data Link Control
| logo         =
| logo alt     =
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| is stack     =
| abbreviation = HDLC
| purpose      = Data framing
| developer    = International Organization for Standardization (ISO)
| date         = {{Start date and age|1979|  |  }}<!--Fill in: Year (4 digits), month and day (2 digits)-->
| based on     = [[Synchronous Data Link Control|SDLC]]
| influenced   =
| osilayer     = [[Data link layer]]
| ports        =
| rfcs         =
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}}

'''High-Level Data Link Control''' (HDLC) is a [[communication protocol]] used for transmitting data between devices in [[Telecommunications|telecommunication]] and [[Computer network|networking]]. Developed by the International Organization for Standardization (ISO), it is defined in the standard ISO/IEC 13239:2002.

HDLC ensures reliable data transfer, allowing one device to understand data sent by another. It can operate with or without a continuous connection between devices, making it versatile for various network configurations.

Originally, HDLC was used in multi-device networks, where one device acted as the master and others as slaves, through modes like Normal Response Mode (NRM) and Asynchronous Response Mode (ARM). These modes are now rarely used. Currently, HDLC is primarily employed in [[Point-to-point (telecommunications)|point-to-point connections]], such as between [[Router (computing)|routers]] or [[Network interface controller|network interfaces]], using a mode called Asynchronous Balanced Mode (ABM).