What happens when overloading an ethernet cable

Question

As the title suggests, what happens when overloading an ethernet cable?

Let's say, I'm using a cat5 cable and transferring 150mbit over it.
What will happen?
Will it slow down to something below 100mbit because it can't handle the 150mbit or will it limit the transfer speed to 100mbit?

Thanks, Pepijn.

Answer 1

Cat 5 cable is good for gigabit speeds (100MHz) so your theoretical 150Mb isn't anywhere near overloading it. If you tried to push a signal down the cable that was too high a frequency, then the inductive and capacitative effects within it would cause the signal to be come increasingly attenuated (degraded). This causes errors and ultimately failure of the path.

I can't find a copyright free image to embed here but there are plenty too look at which demonstrate the frequency response of cat5 cable

Answer 2

The main problem is an electro mechanical problem called cross talk where signals traveling in one direction in your cabling cause interference in the signals traveling in the opposite direction.

Result is corruption in the signal which appears as packet loss on layer 2.

At least that's my layman's understanding :)

Typical copper network cabling has 8 strands or four twisted pairs. By twisting the transmit and return wires you reduce crosstalk but at higher transmission speeds that simple solution becomes insufficient and additional shielding is required.