I (my team) have taken over the implementation and management of a number of floors utilizing out dated over spec cabling. I have a 16 pair UTP line punched down to a 6 port panel as such:
1st port-4 pair
2nd port-1 pair
3rd port-3 pair
4th port-3 pair
5th port-1 pair
6th port-4 pair
Some exceeding lengths of 900 feet or more we are running Cisco 6513s with Cisco 7960 phones. The phones and the switch ports are set to auto negotiate. When the phones come only they negotiate to 100mb/full and they work fine the PCs however will not work at 100/full they have to be dropped down to 10/full before they come online. Now it is my opinion that the negotiation process merely checks to see the if there is a device on either end thatcan run at 100mb/full. The phones with a much lower overhead 64kb do not create sufficient line noise to disrupt (cross talk) the signal enough for communications to fail but nt boxes with their higher overhead and larger communications create more line noise then is acceptable.
I would like to prove on paper to my upper management that the NT boxes mostly will not run at 100/full. I am currently running diagnostics on sample lines to give levels of cross talk attenuation etc. I was wondering if someone knew a little bit of the electrical engineering side of things. I believe my point will be easily proved if I can demonstrate the differences in a 64kb as opposed to 10mb data transfer.
Perhaps I am over my head here.. but what better way to learn.. that and getting the advice of the experts … 😉
thanks
Dustin