Re: [tlug] test of ethernet cable length

[Edward Middleton <emiddleton@example.com>]

Edward Middleton wrote:
> Lars Kotthoff wrote:
>   
>>> recently I have seen a computer with a bios, that could test the length of an
>>> ethernet cable connected to it's NIC.
>>>     
>>>       
>> That was most likely using a special cable/NIC/...
>> The speed of signals through a network cable is near the speed of light, i.e.
>> even if your clock had a resolution of a microsecond it would only be able to
>> measure the length of the cable in multiples of 100m -- assuming that you're
>> able to pinpoint exactly how long it takes the signal to go through the cable.
>> Even when the firmware of the other NIC replies directly to your ping packet or
>> whatever you're sending it's rather unlikely that you'll be able to say exactly
>> how much time it spent processing it (unless you're using specialised
>> hardware).
>>   
>>     
> Some CISCO switches seem to have build-in TDR[1] which could do this and
> more but I can't find any NIC's with built-in support.  What sort of
> card is this?
>   

Interesting the keyword is Virtual Cable Tester[1] but I can't find
anything about Linux support.

Edward

1.
http://www.commsdesign.com/design_corner/showArticle.jhtml?articleID=16505651
http://www.marvell.com/products/vct_soft.jsp