Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!rutgers!bellcore-2!envy!karn
From: karn@envy.bellcore.com (Phil R. Karn)
Newsgroups: comp.protocols.tcp-ip
Subject: re: Are Commercial TCPs Berkeley Code Or Custom?
Message-ID: <1990Aug1.013502.25874@bellcore-2.bellcore.com>
Date: 1 Aug 90 01:35:02 GMT
References: <32140@cup.portal.com> <9007272321.AA09325@asylum.sf.ca.us>
Sender: usenet@bellcore-2.bellcore.com (Poster of News)
Reply-To: karn@thumper.bellcore.com
Organization: Packet Communications Research Group (Bellcore)
Lines: 39


In article <9007272321.AA09325@asylum.sf.ca.us>, romkey@asylum.sf.ca.us
(John Romkey) writes:
|> Phil Karn rolled his own [TCP] in KA9Q (he'll correct
|> me if I'm wrong).

True. My TCP was written from scratch starting in late 1985. Its first
platform, believe it or not, was the Xerox 820, a 64K CPM Z-80 system.
It moved fairly quickly to the PC after that. In the next several
years various refinements such as the Van Jacobson mods were added. It
is fairly stable now, although I recently improved the slow-start code.

My TCP is probably the only one that was written essentially on a
dare. In 1985 the amateur packet radio community was swept by a raging
protocol war that would bring smiles of recognition to this group.  In
one camp were the connection-oriented ISO/CCITT/X.25 lackeys, and in
the other were the Internet TCP/IP people, the only ones who knew what
they were doing (nah, I'm not biased :-)). One of the more rabid
members of the opposing camp stridently argued that TCP was so
incredibly complicated that I could NEVER cram it into anything less
than a full-blown VAX, to say nothing of personal computer hardware
that could be afforded by the average radio ham.

Not one to be told I couldn't do something, I sat down with RFC-793
and started coding.  I had it limping along in a month or two, in time
to show at the ARRL Computer Networking Conference in February 1986.
However, the whole project quickly got into my blood, and over 5 years
later I'm still at it. And the guy who had originally challenged me has
still not conceded defeat.

I *strongly* agree that you can't write a good TCP in a vacuum.  Much
of my early testing took place over a SLIP link which revealed some,
uh, gaps in RFC-793's wisdom on round trip timing algorithms.  Our
CSNET/X.25Net connection to ARPANET at the time was marvelous for
stress testing my IP reassembly and TCP retransmission and
resequencing code. And running on a slow, memory starved machine gave
one a strong incentive to write tight code...

Phil