Consider building a CSMACD network running at 100Mbps over a

Consider building a CSMA/CD network running at 100Mbps over a 500 meter cable with no repeaters. The signal propagation speed in the cable is 2 times 10^8 meter/sec. What is the minimum frame size?

Solution

In order to detect collisions, the station must be still transmittingwhen the first bit reaches thefar endof thecable. For a 500meters(1/2Km) cable, the one­way propagation time is =1µsec so 2=2µsec (RTT). At 100 Mbps all frames shorter than 1000 bits can be completely transmitted in under 2micro­sec. Thus the minimum frame size is 1000 bits or 125 bytes.

This is my assumption.Please check it write or wrong.