Reading about Controller Area Networks and Ethernet standard, I cannot understand why there is a difference in the way the signal is transmitted. Both protocols use twisted pair cables to communicate, with mirroring signals, the logic state being determined as a function of the voltage difference between the two wires.
In CAN networks, CAN Low will range between 1,5V to 2,5V, while CAN High will be in the range of 2,5V to 3,5V.
In an Ethernet network, though, the signal will cross each other and the values will be the exact opposite of each other. So, when one cable will have +3V, the other will have -3V and viceversa.
Why did the engineers choose this particular methods and why isn't just one method used? What are the advantages/disadvantages of each?
Also, in a CAN bus, the wires will be terminated with 120Ohm resistors, to match the line impedance and ameliorate reflections and the end of the cable. I don't think ethernet cables have such terminations. If they are used, are they in the NIC's? If so, how do they account for different wire lengths?