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From: mikeh@bryant.NCD.COM (Mike Harrigan)
Newsgroups: comp.windows.x
Subject: Re: X over a fast modem?
Message-ID: <1883@lupine.NCD.COM>
Date: 5 Oct 90 18:07:58 GMT
References: <1990Oct5.023310.12638@ux1.cso.uiuc.edu>
Sender: news@NCD.COM
Reply-To: mikeh@bryant.NCD.COM (Mike Harrigan)
Lines: 34

In article <1990Oct5.023310.12638@ux1.cso.uiuc.edu>, kadie@cs.uiuc.edu
(Carl M. Kadie) writes:
|> Is it practical to run X over a fast modem?
|> Is V.32 (9600 baud) modem with V.42bis compression fast enough?
|> 
Network Computing Devices has a product called XRemote that allows you
to use our X terminals over RS232 lines either with direct connection
(up to 38.4Kbaud) or on V.32 modems (9600 baud). You can run slower, but
performance suffers.

The way it works is you get special PROMs for the NCD terminal that
contain the X server code and the XRemote communications code. The
XRemote code does both data compression and end-to-end error checking.
On the host computer you need an XRemote binary that provides the
communication at the host side. Currently NCD supplies binaries for
Suns, but we have DEC/Ultrix and DEC/VMS ports underway. Also NCD makes
the source code for XRemote available to systems vendors, so MIPS,
Sequent and others have ports underway.

XRemote does not make use of modem compression because most modem
compression techniques affect latency which causes X applciations to
feel uncoordinated. What works best is a full duplex modem, typically V.32.

You probably want to know about performance of XRemote compared to
Ethernet and/or SLIP. We find that at 9600 baud it is much faster than
SLIP (about a factor of 10), but still not as fast as Ethernet. At 38.4
kbaud you start approaching Ethernet speeds for some applications.
Still, it is a good way of getting X in a remote location at a low price.

If you have more questions, please contact NCD via email at info@ncd.com.

Mike Harrigan
Network Computing Devices
mikeh@ncd.com