Date: Thu, 18 Jan 1996 19:55:24 -0500 (EST) From: Chuck Robey <chuckr@glue.umd.edu> To: marino.ladavac@aut.alcatel.at Cc: questions@freebsd.org Subject: Re: ethernet packet sniffer. Message-ID: <Pine.SUN.3.91.960118194824.8874B-100000@cappuccino.eng.umd.edu> In-Reply-To: <9601181938.AA23886@atuhc16.atusks01.aut.alcatel.at>
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On Thu, 18 Jan 1996 marino.ladavac@aut.alcatel.at wrote: > > > Mike, I'm not saying it would be practical, but if her networking > > department happens to have a Time Domain Reflectometer, which is common > > communications equipment for high speed cables (many cable companies have > > one) then every tap can be detected. A TDR would spot everything, even > > unused BNC taps. > > So would a Frequency Domain Reflectometer. A TDR is an established product from a bunch of vendors, like Tektronix, and unlike a frequency domain reflectometer (?) is calibrated in either feet or meters, so you can hunt down a problem... The fact that your FDR tells you that you have a return at 20 MHz isn't going to help you a whole lot in finding an unknown tap, is it? But a cable company with a TDR is going to know EXACTLY how many TV's you have connected to their cable. A telephone company with a cut T-1 line is going to know exactly how many feet down the road the (open or short) is on the line, so they don't have to go down too many manholes. Splicing crews love TDRs. Enough on this, I'm boring people. Sorry, it's my communications background getting the better of me. > > Which reminds me: we built one of those for some 20 USD worth of parts > (and 5k USD worth of HP signal analyzer, but we had that lying on the > bench already; talking about cheap hack :) > > /Alby > ============================================================================ Chuck Robey chuckr@eng.umd.edu -- I run FreeBSD on n3lxx and Journey2 --------------------------------------------------------------------------- The Dilbert Zone is Dilbert's new WWW home! The area features never-before-seen original sketches of Dilbert, a photo tour of Scott Adams' studio, Dilbert Trivia and memorabilia, high school photos and much more!: <URL:http://www.unitedmedia.com/comics/dilbert/>;
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