For the same assumptions as Exercise F.1, what is the bandwidth of overnight delivery for a 1000-GB package?
Q1:
For the same assumptions as Exercise F.1, what is the minimum bandwidth of the slowest link to beat overnight delivery? What standard network options match that speed?
Q2:
The original Ethernet standard was for 10 Mbits/sec and a maximum distance of 2.5 km. How many bytes could be in flight in the original Ethernet? Assume you can use 90% of the peak bandwidth.
Q3:
Flow control is a problem for WANs due to the longtime of flight, as the example on page F-14 illustrates. Ethernet did not include flow control when it was first standardized at 10 Mbits/sec. Calculate the number of bytes in flight for a 10-Gbit/sec Ethernet over a 100 meter link, assuming you can use 90% of peak bandwidth. What does your answer mean for network designers?
Q4:
Assume the total overhead to send a zero-length data packet on an Ethernet is 100 μs and that an unloaded network can transmit at 90% of the peak 1000-Mbit/sec rating. For the purposes of this question, assume that the size of the Ethernet header and trailer is 56 bytes. Assume a continuous stream of packets of the same size. Plot the delivered bandwidth of user data in Mbits/sec as the payload data size varies from 32 bytes to the maximum size of 1500 bytes in 32-byte increments.
Q5:
Exercise F.6 suggests that the delivered Ethernet bandwidth to a single user may be disappointing. Making the same assumptions as in that exercise, by how much would the maximum payload size have to be increased to deliver half of the peak bandwidth?
Q6:
One reason that ATM has a fixed transfer size is that when a short message is behind a long message, a node may need to wait for an entire transfer to complete. For applications that are time sensitive, such as when transmitting voice or video, the large transfer size may result in transmission delays that are too long for the application. On an unloaded interconnection, what is the worst-case delay in microseconds if a node must wait for one full-size Ethernet packet versus an ATM transfer? See Figure F.30 (page F-78) to find the packet sizes. For this question assume that you can transmit at 100% of the 622-Mbits/sec ATM network and 100% of the 1000-Mbit/sec Ethernet.
Q7:
Exercise F.7 suggests the need for expanding the maximum payload to increase the delivered bandwidth, but Exercise F.8 suggests the impact on worst-case latency of making it longer. What would be the impact on latency of increasing the maximum payload size by the answer to Exercise F.7?