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Posting-Version: version B 2.10.2 9/18/84; site watcgl.UUCP
Path: utzoo!watmath!watcgl!dmmartindale
From: dmmartindale@watcgl.UUCP (Dave Martindale)
Newsgroups: net.unix-wizards
Subject: Re: uucp through flow-controlled (XON/XOFF) network
Message-ID: <509@watcgl.UUCP>
Date: Tue, 20-Nov-84 13:43:53 EST
Article-I.D.: watcgl.509
Posted: Tue Nov 20 13:43:53 1984
Date-Received: Wed, 21-Nov-84 00:03:58 EST
References: <5805@brl-tgr.ARPA> <4651@utzoo.UUCP>
Organization: U of Waterloo, Ontario
Lines: 16

> Question: Should uucp be able to function over a flow-controlled
> 	network that uses XON/XOFF as flow control.

As others have pointed out, if your network can handle moderate-length
bursts of data without losing it, uucp's own windowing scheme will work.
But sometimes, you HAVE to have flow control between the CPU and the
network - an example is Sytek Localnet, which is arbitrarily slow depending
on how congested the network is right now.

One simple fix (well, kludge) is to add a simple byte-stuffing layer
underneath the packet driver, which takes any XONs, XOFFs, and other
objectionable characters (some I/O packages won't transmit NUL, for
example) and encode them as a unique sequence of two characters
before transmission, performing the reverse transformation at the other
end.  This allows the use of flow control, and slows things down only a
little since only a few bytes get expanded.  More CPU overhead, though.