Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!orion.oac.uci.edu!meggers
From: meggers@orion.oac.uci.edu (mark eggers)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Why do TCP connections hang?
Summary: bit mangling
Message-ID: <3740@orion.cf.uci.edu>
Date: 1 Dec 89 00:07:50 GMT
References: <8911301020.AA14662@hayes.fai.alaska.edu>
Organization: University of California, Irvine
Lines: 24

Bill,
     One thing that may be biting you is a particular bit pattern. If you 
have marginal connections to the rest of the world, or if your 
CSU/DSUs are a bit flakey, they can mangle certain bit patterns. We 
had this happen with a connection on CERFnet from here at UCI to 
SWRL (Cal State University net). PacBell and Brian Roode (another 
member of our network team) found the flakey link between Seal 
Beach and Long Beach. I think that they found it by doing extensive 
BERT (bit error rate tests) tests. 
     Since you seem to be on the track of this problem, you might try 
to artificially generate the bit pattern in a file (a quick and dirty C 
program), and then do a binary FTP to another system. If the FTP 
hangs, then you have some cause to suspect that bit pattern. You 
might want the circuit provider to then run a BERT test using the 
suspected pattern and watch for errors.
     At that point, you can then start replacing things to bring the 
error rate down.

Of course, this is just a guess (with 2 hours of sleep at that ;-) ).

Good luck - Mark Eggers, Network Communications Analyst
            University of California, Irvine

email:      meggers@uci.edu


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