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From: news@bbn.COM (News system owner ID)
Newsgroups: comp.dcom.lans,comp.dcom.modems
Subject: Re: Protocol spoofing in terminal servers (was: Re: SL/IP capable terminal servers)
Keywords: Cisco, Annex II terminal servers with SL/IP.
Message-ID: <50007@bbn.COM>
Date: 21 Dec 89 17:05:34 GMT
References: <993@scifi.UUCP> <910@ursa-major.SPDCC.COM> <915@ursa-major.SPDCC.COM> <13531@s.ms.uky.edu>
Reply-To: pplacewa@antares.bbn.com (Paul W Placeway)
Organization: Bolt Beranek and Newman Inc., Cambridge MA
Lines: 41

In article <13531@s.ms.uky.edu> david@ms.uky.edu (David Herron -- a slipped disk) writes:
< How'z'about spoofing various protocols inside the terminal server?

Hmmm.  Maybe, but it would depend on a lot of other things...

< In this case the problem, as I see it that is, is that if you do
< a kermit through a terminal server you're often sending tiny 1-5
< character packets through the net.  If you could fix things so lots
< of those small packets would coalesce into larger ones then the
< impact on the network would lessen greatly.  Throughput should also
< dramatically improve..
< -- 
< <- David Herron; an MMDF guy                              <david@ms.uky.edu>

One problem with this is: how does the terminal server figure out
where the eg. Kermit packets are going?  For instance, I could be
telnetting to a modem-server, and going back out onto phone wires from
there (don't laugh -- it's a quite effective way of using a set of
outgoing or bidirectional modems).

Also, even if I was just telnet-ing/rlogin-ing to a local host, how do
you set up the secondary connection?  Do you want to let your terminal
server setup FTPs without passwords (I don't).  What if I have done
something like this:

	program_foo | kermit -s -


On the other hand, terminal servers could be (and are) made to detect
higher rates of IO and do more reasonable things as a result.
Actually, if you follow the Telnet RFCs correctly, this will all work
out right.

And, of course, the serial-line-transfer protocols should be smart
enough to handle this sort of thing with some amount of grace.  Kermit
with windowing is (but windowing c-kermit is still in pre-alpha
development).  Mearly setting up the packet size as large as you can
get away with helps greatly.

	-- Paul Placeway; MacKermit coord and serial hacker in general
	   <pplaceway@bbn.com>