Don't know what it is however I was at an audio show several years ago and they had a training room set up for the dealers. They were demonstrating the difference in ethernet cables. Lo and behold there was a difference. You can try for yourself with a cheap cable versus a name brand cable you will see the difference.
ETHERNET CABLES
When using ethernet for hooking up streaming devices and dacs, what cat level of ethernet cable should be used. Is there any sonic improvement by going to a higher dollar cat 7 or 8 cable?