Token Bucket: Time the Host Can Transmit at Full Rate

Given: peak transmission rate $R_{out} = 6$ Mbps, token generation rate $r = 1$ Mbps, bucket capacity $B = 8$ megabits, bucket initially full.

Reasoning

The host may send at the full 6 Mbps only while the bucket still holds tokens. During transmission the bucket is simultaneously being refilled, so tokens are consumed at the net rate:

$$r_{net} = R_{out} - r = 6 - 1 = 5\ \text{Mbit/s}$$

The initial 8 Mbit of tokens therefore lasts:

$$t = \frac{B}{r_{net}} = \frac{8\ \text{Mbit}}{5\ \text{Mbit/s}} = 1.6\ \text{s}$$

Verification

In $t = 1.6$ s:

• tokens used = $6 \times 1.6 = 9.6$ Mbit
• tokens available = initial $8$ Mbit + refilled $1 \times 1.6 = 1.6$ Mbit = $9.6$ Mbit

Both match, so the bucket empties exactly at $t = 1.6$ s. After that the host is limited to the sustained rate of 1 Mbps.

Final answer: the computer can transmit at the full 6 Mbps for 1.6 seconds (sending 9.6 Mbit), after which it is throttled to 1 Mbps.