Andrew S. Tanenbaum Edition 5 Exercise 4 Question 6 (Page No. 351)

Question

What is the length of a contention slot in CSMA/CD for (a) a 2-km twin-lead cable
(signal propagation speed is 82% of the signal propagation speed in vacuum)?, and (b)
a 40-km multimode fiber optic cable (signal propagation speed is 65% of the signal
propagation speed in vacuum)?

Answer 1

for a) part:

0.001626 seconds.

use formula: Tt>=2*Tp

Answer 2

a. Propagation speed in twin lead=$2.46*10^8 m/s$

     Signal propagation speed=$0.82*2.46*10^8 m/s$

     d=2000 m

     $T_{p}=\frac{2000}{0.82*2.46*10^8}$ sec

     Contention Period=$2T_{p}=\frac{2*2000}{0.82*2.46*10^8}$ sec

b. Propagation speed in multimode fiber=$1.95*10^8 m/s$

     Signal Propagation speed=$0.65*1.95*10^8 m/s$

     Contention Period=$\frac{2*40000}{0.65*1.95*10^8}$ sec