What figure do you use when cabling CAT6 cable. Outside footage on the jacket or length of longest pair in the cable taking into consideration the twist?

[tterry5966]

I have some cable runs, CAT6, that are per the jacket measurements close to 300ft. They are failing certification test due to distance. The vendors equipment is reading 350ft due to the number of twist in the longest pair. If spec says that the distance CAT6 will push gigabit speeds in 100meters (328ft) do you use jacket measurements or longest pair measurements, and how do you know how long a run can be if you do not know the length of the longest pair?

[Edwin Summers]

If I remember correctly, the TIA recommendations are no more than 90m for the horizontal cabling run, allowing 5m at each end for the associated patch cabling.  Sounds like your particular situation exceeds this and is pushing the Ethernet standard.

I'm assuming a TDR is being used to measure the length.  Ensure that the appropriate settings are in use (nominal velocity of propagation or whatever parameters the device allows).

Regardless, you may end up in a semi-gray area technically (where two results contradict), which will likely result in an overruling and more pronounced administrative/political/business area.  If I were the customer in this instance, I'd likely consider it a fail given the above (measurement well over the spec; estimate based on jacket markings likely over spec) provided there are no mitigating circumstances.

I look forward to other responses on your last question.  I typically take a quite conservative approach...keeping to under the spec max distance and leaving allowances when estimating cable distance during the pre-install survey.  If the distance approaches the max limit, fiber is recommended.

Best of luck!