Complete Question:
Recall that with the CSMA/CD protocol, the adapter waits K. 512 bit times after a collision, where K is drawn randomly. a. For first collision, if K=100, how long does the adapter wait until sensing the channel again for a 1 Mbps broadcast channel? For a 10 Mbps broadcast channel?
Answer:
a) 51.2 msec. b) 5.12 msec
Explanation:
If K=100, the time that the adapter must wait until sensing a channel after detecting a first collision, is given by the following expression:
The bit time, is just the inverse of the channel bandwidh, expressed in bits per second, so for the two instances posed by the question, we have:
a) BW = 1 Mbps = 10⁶ bps
⇒ Tw = 100*512*(1/10⁶) bps = 51.2*10⁻³ sec. = 51.2 msec
b) BW = 10 Mbps = 10⁷ bps
⇒ Tw = 100*512*(1/10⁷) bps = 5.12*10⁻³ sec. = 5.12 msec
```
#!/usr/local/bin/python3
import sys
coins = { "quarters" : 25, "dimes" : 10, "nickels" : 5, "pennies" : 1 }
def mkChange( balance, coin ):
qty = balance // coins[ coin ]
if( qty ):
print( str( qty ) + ' ' + coin )
return( balance % coins[ coin ] )
if( __name__ == "__main__" ):
if( len( sys.argv ) == 2 ):
balance = int( sys.argv[ 1 ] )
balance = mkChange( balance, "quarters" )
balance = mkChange( balance, "dimes" )
balance = mkChange( balance, "nickels" )
balance = mkChange( balance, "pennies" )
else:
sys.stderr.write( "\nusage: " + sys.argv[ 0 ] + " <change owed>\n" )
```
Answer:
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