High-Level Data Link Control
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High-Level Data Link Control (HDLC) is a bit-oriented code-transparent synchronous data link layer protocol developed by the International Organization for Standardization (ISO). The standard for HDLC is ISO/IEC 13239:2002.
| Communication protocol | |
| Abbreviation | HDLC |
|---|---|
| Purpose | Data framing |
| Developer(s) | International Organization for Standardization (ISO) |
| Introduction | 1979 |
| Based on | SDLC |
| OSI layer | Data link layer |
HDLC provides both connection-oriented and connectionless service.
HDLC can be used for point-to-multipoint connections via the original master-slave modes Normal Response Mode (NRM) and Asynchronous Response Mode (ARM), but they are now rarely used; it is now used almost exclusively to connect one device to another, using Asynchronous Balanced Mode (ABM).