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From: ddb@viper.UUCP (Bennet)
Newsgroups: comp.emacs
Subject: Re: What's wrong with flow control?
Message-ID: <388@viper.UUCP>
Date: Sat, 29-Nov-86 14:36:51 EST
Article-I.D.: viper.388
Posted: Sat Nov 29 14:36:51 1986
Date-Received: Sat, 29-Nov-86 21:04:06 EST
References: <3910001@nucsrl.UUCP>
Reply-To: ddb@viper.UUCP (David Dyer-Bennet)
Organization: Lynx Data Systems, Minneapolis, MN
Lines: 16
Summary: it's negative

I don't know what RMS considers brain-damaged about ^S / ^Q flow
control (other than the obvious problem that it uses up two keys
that have obvious mnemonics in a text editor).  I, however, think that
a "positive" flow control scheme will in general be more reliable than
a negative one like xon/xoff.  The problem with a negative scheme is
that at every stage where the things are handled, there are some critical
response requirements; if you don't stop sending fast enough after you
receive your ^S, you will overrun the buffer in your receiver.

A positive system, on the other hand, works by saying "You may now send
me up to 15 characters".  You do so.  Nobody has to jump around trying
to avoid timing windows.  DEC uses something like this in their LAT 
protocol on Ethernet.  There's also some sort of a variant on this in
some older microcomputer terminal protocols, if I remember correctly.

		-- David Dyer-Bennet