Re: ethernet monitor needed?


Jeff Stearns (fluke!jeff@beaver.cs.washington.edu)
22 Mar 88 22:15:39 GMT


In article <In article <3447@cbmvax.UUCP>, In article <3447@cbmvax.UUCP>, grr@cbmvax.UUCP (George Robbins) writes
about his search for Ethernet test gear.

I'll put in a plug for the Cabletron LAN-MD. It's a suitcase-sized box that
can thoroughly test cables and transceivers. A pair of LAN-MD's can exercise
transceivers in place and tell you things that you'll never otherwise know.

Which of your transceivers have broken or out-of-spec collision detect
circuitry? How will you find them? Hint: Can a computer tell if its
transceiver has this problem?

Now that we're in the age of level I vs level II vs 802.3, we have abundant
opportunities to pair up Ethernet controllers with the wrong kind of
transceiver, multiplexor, or cable. Physical and link-level problems like
this are often inscrutable to higher-level tools.

Imagine a chart of the ISO reference model. Stick a pushpin in it for every
Ethernet problem you've had. Here's a starter drawn from recent memory:
    Controllers that don't conform to the Ethernet spec, wrong cable type for
    transceiver level, out-of-spec transceivers, defective transceivers,
    broken Ethernet controllers, buggy controllers, buggy device drivers,
    improperly-installed vampire taps, noise-sensitive transceivers, loose
    transceiver cables, bugs in TCP/IP, NFS, ND, and ftp.

That puts a lot of pins down at the bottom of the chart, below the level of
monitors and protocol analyzers. The LAN-MD works well down there.
I wouldn't be surprised if Cabletron were working on something newer than
the LAN-MD; you might also want to ask 'em that.

--
		 Jeff Stearns
	 Domain: jeff@tc.fluke.COM
	  Voice: +1 206	356 5064
    If you must: {uw-beaver,microsoft,sun}!fluke!jeff
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