GATE 2016 - 1 - 54 with modification

Question

For a host machine that uses the token bucket algorithm for congestion control, the token bucket has a capacity of 1 mega byte and the maximum output rate is 20 mega bytes per second. Tokens arrive at a rate to sustain output at a rate of 10 mega bytes per second. The token bucket is currently empty and the machine needs to send 12 mega bytes of data. The minimum time required to transmit the data is _____________ seconds.

Comments

since token bucket is initially empty, there will be no initial burst transfer. throughout transmission, effective outgoing rate will be rate at which token arrive, therefore,

outgoing rate = 10 MBPS, total data = 12 MB

time taken = 12/10 = 1.2 secs

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@joshi

shouldnt it be the difference betweeen output rate and input rate ?

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The difference between output and input rate(relative transmission rate) is 10 MBps.

Which means two task are happening simultaneously one outgoing which twice the input rate so there will be no condition like congestion or packet loss.

So you need to only calculate the time taken to arrive data at the router which is

1 sec ------ 10MB

1.2sec ------- 12MB

.