Re: fiber

[John Kramer <jbkramer@mad.scientist.com>]

> 
> I have seen patchcords with a 3inch length stripped near the jack, and 
> working on 10MBps.  I have seen a patch panel, with the ENTIRE panel 
> patched with 2' lengths of wire, nicely bundled and routed, though of 
> course they had no twists with respect to each other any longer.  And this 
> guy, in 1995, had given a certificate that the network was "CAT-5 
> Certified" and "Future Proof".  This was a AT&T vendor, with Krone 
> certification as well.

The problem there is you are suspect to noise and crosstalk, as has been
pointed out.  You may have difficulty running at 100mbps or higher on more
than a few of those cables.  Basically, that network is NOT cat-5
certified, and the certificate is a fraud.

> 
> >I'm more concerned about observing the pairings so that the right
> >signal lines are paired, and have seen more noise-related problems as
> >a result of illogical pairings than short runs of parallel conductors.
> 
> I have rarely, and I do not use this word lightly, seen wire 3 & 6 twisted 
> together.  Practically all the cabling vendors I have seen patch a 1-2, 
> 3-4, 5-6, 7-8 style.  The network works, so they have been doing this for 
> years, and they see no reason to change.  This includes AT&T/IBM/AMP 
> "specialists".  Most installations are in offices, so the overdesign in the 
> standard shield bad installations.  And most vendors chant the "Structured 
> Cabling" mantra, more often than not to push a Patch Panel in.

I don't know who you are using for a cabling vendor.  It should always be
with a 1-2, 3-6, 4-5, 7-8.  Otherwise you end up with a split pair and
the physical layer of ethernet cannot eliminate line noise.

Better find a REAL wiring vendor, and audit their work.  At least here in
the backwoods of Indiana we can find specialists to do it
right.  (sometimes you gotta prod 'em, though)

It comes down to this: know the specs.  Audit the installers.  Harass them
about it and let them know up front that you want cat-5 specs and you will
hold them to that.  Just passing a line test isn't enough; the cabling
needs to be run properly so that it will last.  Break out your ladder and
double check when they are installing.

Maybe I'm being redundant, and I really haven't been following much of
this thread, but I felt it had to be said.  Ok, I'm going to bed now.

--
John B. Kramer  
jbkramer@mad.scientist.com
http://24.17.57.58/~yoda