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From: dp@JASPER.PALLADIAN.COM (Jeffrey Del Papa)
Newsgroups: comp.sys.apollo
Subject: ethernet diagnostics
Message-ID: <870605145331.2.DP@BANFF.PALLADIAN.COM>
Date: Fri, 5-Jun-87 14:53:00 EDT
Article-I.D.: BANFF.870605145331.2.DP
Posted: Fri Jun  5 14:53:00 1987
Date-Received: Wed, 10-Jun-87 01:10:34 EDT
References: <134@stag.UUCP>
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: Jeffrey Del Papa <DP%JASPER@LIVE-OAK.LCS.MIT.EDU>
Distribution: world
Organization: The ARPA Internet
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    Date: 5 Jun 87 07:09:17 GMT
    From: umnd-cs!umn-cs!meccts!nis!stag!trb@rsch.wisc.edu  ( Todd Burkey )

    Also, I was wondering how breaks in the ethernet cable are so precisely
    pinpointed by software on unix? (ala...I recall messages like: Connection
    failed-You have a break in your cable 24 meters from node x). I assume that
    some sort of signal reflection measurement was used, but wasn't sure if this
    was done by the host software or some fancy code on the etherne board itself.
    Thanks in advance for any help.
      -Todd Burkey
      ihnp4!meccts!stag!trb
			     (don't do a trb@stag.UUCP, since my map keeps getting
			      lost by the local net gods...should be out again soon


Some ethernet intrface cards (all the older interlan?) have a builtin TDR (time domain
reflectometer) which if you incant the right thing at the card will find breaks and
shorts.

<dp>