ISP Glossary Find an ISP Term

Search ISP Sites

Search: Search internet.com

ISP Resources ISP-Lists ISP Glossary ISP News CLEC-Planet The List ISPCON Free Newsletter IT Developer Internet News Small Business Personal Technology Search internet.com Advertise Corporate Info Newsletters Tech Jobs E-mail Offers internet.commerce Be a Commerce Partner

Search for an ISP term
by a keyword...	...or by category. choose one... Communications Computer Industry Companies Computer Science Data Graphics Hardware Internet and Online Services Mobile Computing Multimedia Networks Operating Systems Programming Software Standards Types of Computers World Wide Web

HDLC Last modified: Tuesday, April 29, 1997
Short for High-level Data Link Control, a transmission protocol used at the data link layer (layer 2) of the OSI seven layer model for data communications. The HDLC protocol embeds information in a data frame that allows devices to control data flow and correct errors. HDLC is an ISO standard developed from the Synchronous Data Link Control (SDLC) standard proposed by IBM in the 1970's. For any HDLC communications session, one station is designated primary and the other secondary. A session can use one of the following connection modes, which determine how the primary and secondary stations interact. Normal unbalanced: The secondary station responds only to the primary station. Asynchronous: The secondary station can initiate a message. Asynchronous balanced: Both stations send and receive over its part of a duplex line. This mode is used for X.25 packet-switching networks. The Link Access Procedure-Balanced (LAP-B) and Link Access Procedure D-channel (LAP-D) protocols are subsets of HDLC.
HDLC LAPB Level 2 protocol Describes HDLC Link Access Procedure Balanced (LAPB). HDLC Overview Provides an overall description of the HDLC protocol including details on the basic framing structure. SDLC protocol overview Describes the HDLC implementation of SDLC (HDLC Normal Response Mode).	Related Categories Networking Standards Related Terms communications protocol frame OSI