Talk:High-Level Data Link Control

History

So was SDLC derived from HDLC (by removing the balanced modes), HDLC derived from SDLC (by adding the balanced modes), or were both derived from some third protocol? Guy Harris 10:48, 27 December 2005 (UTC)[reply]

No, it was the other way around. The original SDLC was asymmetric and when it was taken into the US ANSI committee X3S3 it was extended to a symmetric mode as well.

My question is how can you have a history section with no dates!? When did HDLC work start and when was the first version of the standard approved? —The preceding unsigned comment was added by 24.34.102.194 (talk • contribs) 10:23, 3 June 2006 (UTC).[reply]

Extra information?

Should the section on bit stuffing be reduced to a simple link to the bit stuffing page?

What is "loop-mode" vs. "point-to-point" vs. "multidrop" HDLC?

About bidirectional communications

Hello,

After reading the article there is something I still don't understand. How can we get a full duplex communication over a single channel? The protocols that run over HDLC need to speak both ways. Is there some kind of turns based on 7Eh exchanges? —The preceding unsigned comment was added by 85.54.149.35 (talk) 14:28, 1 February 2007 (UTC).[reply]

HDLC protocol is designed to run over EIA-422 hardware, which implements full-duplex communication.

The hardware has a dedicated "outgoing" twisted pair of wires and a separate "incoming" twisted pair (4 wires total), typically all bundled in a single cable.

For a particular pair, the HDLC data always flows in the same direction -- it never "turns around".

However, the LocalTalk article implies that the Zilog SCC (a HDLC transciever) both transmits and recieves over the *same* pair of wires. Did that use an extension to HDLC, or some completely different protocol?

--76.209.28.72 19:11, 5 June 2007 (UTC)[reply]