Great progress. As people overtrumps each other, we will soon have a complete solution :)

By the way - a cable can have many properties that may be analyzed. But not all properties are constant enough that they will give a reasonably good estimate of the length. That is of course the reason why normally only one of the suggested methods are used in real life. That measurement method is also directly available in some network cards, where the computer BIOS or utility program can inform about cable length and potential short or break (and the distance to the potential error).