Talk:High-Level Data Link Control/Archive 1

Archive 1

Definition

How can HDLC be defined as a synchronous protocol when later in the page there are asynchronous modes mentioned? Drumroll99 20:19, 9 May 2009 (UTC)

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)

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).

It is mentioned here that HDLC draft existed in Feb. 1973: https://www.rogerdmoore.ca/PS/CYCLB.html — Preceding unsigned comment added by Litvindev (talk • contribs) 22:46, 10 August 2019 (UTC)

Extra information?

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

Yeah, it should IMO. Right now, the information about bit stuffing is there twice in this article, and one description is even wrong. I'll probably get to it in the near future (if nobody disagrees, of course). --Kraymer (talk) 13:18, 18 March 2011 (UTC)

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).

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)

RS-232 has TxD, RxD, and ground lines. A transceiver sends data on the TxD line and receives it on the RxD line; signals on both lines are relative to the common ground line. Data can be transmitted in both directions at the same time. I don't know whether that was used for any form of synchronous networking, but it was definitely used for asynchronous communications. Guy Harris 20:08, 5 June 2007 (UTC)