Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!opus.cray.com!dab
From: dab@opus.cray.com (Dave Borman)
Newsgroups: comp.protocols.tcp-ip
Subject: Re:  TELNET Buffering Woes
Message-ID: <8905021526.AA03195@oliver.cray.com>
Date: 2 May 89 15:26:53 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 23

> A user with a dumb terminal connected to a terminal server (in this
> case a U.B. NIU-180) or with a PC connected directly to the Ethernet
> TELNETs into the Pyramid which is connected to the Ethernet.
> The user then "cat"s a large file to the screen, immediately tries to
> abort with a control-c. The output keeps coming for a long time.

The problem here is not with the remote machine, but with the local
telnet implementation.  The way that things should work is:
	User types ^C
	Local telnet translates that to, and sends, IAC IP,
		and then sends IAC DO TIMING-MARK and begins to
		flush all output.
	Local telnet receives IAC WILL/WONT TIMING-MARK, and
		resumes terminal output.

The problem is that many telnet implementations are very dumb.  They
are not doing local recognition of the interrupt character, and thus
they don't know when to send the DO TIMING-MARK and start output flushing.

The 4.3 telnet has an option "localchars" which when enabled causes
telnet to do the above stated procedure.

			Dave Borman, dab@cray.com