Time for monitoring station


#1

Consider a token ring network with a length of 2 km having 10 stations
including a monitoring station. The propagation speed of the signal is 2
× 108 m/s and the token transmission time is ignored. If
each station is allowed to hold the token for 2 μsec, the minimum time
for which the monitoring station should wait (in μsec)before assuming
that the token is lost is _______.


#2

Length L = 2km = 2 (10^3) m , number of stations N = 10, Speed of signal = 2 108 m/s , tokne holding time for each station = 2 * 10-6 sec.

Now, when will station assume the token is lost? When the token is not reached to him after the maximum time limit.

Ok, what is this maximum time limit?

Maximum time limit wil be the sum of => time taken for token to pass through the ring ( Ring latency) ,+ time taken by all the station for holding token.

So, 1) time taken for token to pass through the ring = Length of ring/ speed of signal = (2 * 103 ) m / (2* 108 m/s ) = 10-5 sec

10-5 sec = 10 * 10-6 sec = 10 µsec.

  1. Time taken by all the stations for holding token = Number of stations * 2 µsec = 10 * 2 µsec = 20 µsec…No… There is a catch here. Because we are calculating this time for 1 particular station and in this holding time ( 20 µsec) ,we have included it’s time too. Station will start waiting after it releases the token, So ideally we should not include its time i.e. 2 µsec.

total time would be 10 + 18 µsec = 28 µsec.

Answer would be 28 µsec