How can 100Base-T achieve 100 meter distance at 125Mhz clock?

Question

I admit I have some large holes in my understanding of this topic, but it seems like you run into physical limitations of the speed of light.

If the speed of electricity through copper is about 280,000,000 meters per second, and the clock on the ethernet card is running at 125Mhz (found this online, not sure if this is the right speed), the signal should only be able to travel about 280,000,000 * (1/125,000,000) = ~2.24 meters before the next clock cycle starts.

Assuming only 1 bit can be on a wire at a time (possibly a bad assumption), how is 100 meters possible?

Answer 1

Your assumption that only one bit can be on the wire at a time is completely incorrect. Your calculations can compute how far apart the signals on the wire are, but all the bits of the entire frame can be on the wire at the same time.

You also need to understand that one data bit does not equal one bit on the wire. You will need to understand the encoding used to figure that out.