Newsgroups: comp.protocols.iso
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From: mskuhn@faui09.informatik.uni-erlangen.de (Markus Kuhn)
Subject: Re: Status of HDLC Standard (1/12/90)
Message-ID: <mskuhn.670765130@faui09>
Keywords: HDLC,ISO
Organization: CSD., University of Erlangen, Germany 
References: <mskuhn.670597503@faui09> <mskuhn.670600487@faui09>
Distribution: comp
Date:  4 Apr 91 11:38:50 GMT
Lines: 64

This has been posted recently to comp.dcom.modems and might
also be interesting for people here in comp.protocols.iso:

From: tnixon@hayes.uucp
Date: 3 Apr 91 11:21:07 GMT

In article <mskuhn.670600487@faui09>,
mskuhn@faui09.informatik.uni-erlangen.de (Markus Kuhn) writes: 

> Has anybody information about the following two extentions
> to HDLC:
> 
>   - Extended Transparency Options for Start/Stop Transmission
>   - Seven-bit Transparency Option for Start/Stop Transmission

You should be able to get these PDAMs through your country's ISO 
national body (DIN).  The original work on these proposals was done 
here at Hayes back in 1985, and I presented them in the standards 
bodies initially back in 1986.  ANSI X3S3.4 decided to push first 
for the standardization of the basic Start/Stop HDLC (AD 1) rather 
than try to explain the whole package to ISO/IEC JTC 1/SC 6/WG 1 all 
at once.  I haven't been attending meetings of either of these 
committees for a couple of years, but apparently the current members 
of X3S3.4 have followed through and submitted the additional 
portions of the original Start/Stop HDLC proposal to ISO for 
consideration.

> Are there any standards (V.42ter, X.32bis, ???) in development
> that use Start/Stop HDLC?

CCITT Study Group VII has initiated work on adding the Start/Stop 
HDLC framing mode to X.25 and X.32.  I do not know the current
status of that work, except that I know it's not done yet.  A lot of 
PTTs and PSPDNs are very interested in it because of the potential 
market for value-added services to async-only PCs (without the need 
to add an HDLC card and synchronous modem).

> Are there any modems that use Start/Stop HDLC and convert it in
> normal HDLC?

I am not aware of any.  Hayes V-series modems support Start/Stop 
HDLC in two ways:  Start/Stop LAPB protocol to retrofit error 
control features on older, async-only modems like the Smartmodem 
1200; and, Start/Stop X.25 (which is pretty useless right now, since 
no network supports it yet!).  But they don't provide direct 
pass-through conversion from Start/Stop HDLC to sync HDLC.  Our 
modems DO provide the "Hayes AutoSync" feature, which permits 
conversion in the modem between async and sync data streams, but the 
async data format is not according to 3309/AD 1 (it is simpler; no 
transparency required, and the FCS calculation is done in the 
modem).

	-- Toby

-- 
Toby Nixon, Principal Engineer    | Voice   +1-404-840-9200  Telex 151243420
Hayes Microcomputer Products Inc. | Fax     +1-404-447-0178  CIS   70271,404
P.O. Box 105203                   | UUCP uunet!hayes!tnixon  AT&T    !tnixon
Atlanta, Georgia  30348  USA      | Internet       hayes!tnixon@uunet.uu.net


--
Markus Kuhn, Computer Science student
University of Erlangen, Germany
