High-Level Data Link Control
- A link-level protocol used to provide reliable point-to-point transmission of a data packet. Note: A subset of HDLC, known as "LAP-B," is the layer-two protocol for CCITT Recommendation X. 25. See also Advanced Data Communication Control Procedure, data, data transmission, level, link, Open Systems Interconnection--Reference Model, synchronous data link control, X. -series Recommendations.