Head down to the transport layer description and there you will find the portion that could retransmit.
Wiring specs at http://en.wikipedia.org/wiki/Category:Ethernet_cables. Note the cat5 standard had NO crosstalk specifications. And check out the list of insulations you can use!
They also note that there is solid and stranded available.
Just as with any other wire - speaker, interconnect, power etc., you can also have different grades of network wire.
The TCP/IP part applies ONLY if you use your home network to send music to your system.
Oh - and don't go down to the box store and pay $20 for a 6 foot cat6 wire. If you don't have a local supplier get it on line. As with the rest of the components you can buy there are places that will take your money and laugh all the way to the bank!