[nsp] protcol keep boucing.

[warner at cats.UCSC.EDU]

>Say router is at 40th floor and teleco demarc is at bassement of bhe
>building, from the past experiance, cisco 1700/1600 does not seem to
>keep procotol up all the time. ie teleco signal seems to be okay but for
>some reason, protcol does not seem to ride on it.
>
>Is there any rule of sum that I can use find out the limilation of the
>length? What do you suggest?

I have seen Cisco built-in CSUs show sensitivity to crosstalk when
their T-1s are extended from the demarc.  It is best if the T-1 pairs
are from different binder groups in the building riser cable.  If you
are using t-screen cable and the shield is grounded, you should be
OK, too.  If you are using dedicated IWs, you should use two separate
cables to keep some distance between the pairs.

Another pernicious situation is where you think you're running a 4-wire
(2 pair) circuit but one of the wires is open.  In this case, the lone
wire will work against a return path on the other pair and give you
a noisey signal.  It works, but badly.  One thing I do when I need to 
make sure this isn't a problem is lift the bridge clips and look at 
all possible combinations in both directions with a simple ohm meter.  
None of the wires should show an open circuit to any of its cousins.

-jim warner, UC Santa Cruz