Date: Sat, 20 Sep 1997 18:21:23 +0200 (CEST) From: hm@kts.org (Hellmuth Michaelis) To: freebsd-hackers@freebsd.org Subject: Re: ISDN Modems Message-ID: <m0xCSHb-00023GC@bert.kts.org> In-Reply-To: <Pine.BSF.3.91.970920100834.15878B-100000@bmccane.uit.net> from Wm Brian McCane at "Sep 20, 97 10:10:58 am"
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Wm Brian McCane wrote:
> > I can get (depending on the quality of the connection) the maximum
> > throughput of ~8kB/sec (well, actually ~7.5kB/s with overhead).
[...]
> Only 7.5kB/sec? I am now very confused.
An ISDN B-channel has a maximum transfer rate of exactly 8 kB/sec. Using
ftp over such a line ends up with something close to 7.5 kB/sec uncompressed.
> Do any of the plug-in cards do LZ compression, or anything similar?
Some active ISDN cards do compression, for some time it seemed V.42 were
the standard the manufacturers would agree upon, but they didn't. (if i
recall it correctly, V.42 compresion is supported under V.120, but i'm
not shure).
There is no standard interoperable way of doing compression on the B-channel,
many proprietary solutions exist; the only standard in this environment is
doing PPP over ISDN which gives you the usual (some also proprietary, i.e.
STAC compression) compression schemes.
hellmuth
--
Hellmuth Michaelis hm@kts.org Hamburg, Europe
"Those who can, do. Those who can't, talk.
And those who can't talk, talk about talking." (B. Shaw)
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