Token generation or refresh rate: Token Bucket

Question

Consider a token bucket with maximum rate = 20 Mbps. Suppose we want to make sure that maximum rate can only be sent for atmost 5 sec at a time and atmost 150 Mb can be sent over 10 sec window. Computer the required value for token refresh rate?

Comments

Yes! Token bucket capacity is 50Mb

---

why did you subtract 10 from 20 ?

---

@Ashwin but here we don't have packet size, so when the packet came we have to attach a token along with the packet and then send the packet.

ryt?

Answer 1

For 5s, data are sent with maximum bandwidth after that inflow rate = outflow rate = x Mbps.

Here C is the capacity of the bucket and the inflow rate is xMbps.

Maximum data can be sent in 5s : C + 5x

Maximum average rate: $\frac{C +5x}{5}$

$\frac{C +5x}{5}$ = 20

=> C + 5x = 20 X 5

=> C + 5x = 100

So data sent till now is 100 Mb for 5s.

Also, given in the question “ atmost 150 Mb can be sent over 10 sec”. Left time is 5s.So, for sending remaining 50Mb, we have time 5s.

Now outflow rate = inflow rate. So, outflow rate is x Mbps.

Therefore, $\frac{50}{x}$ = 5

=> x = 10

Therefore refresh rate is 10Mbps.