Computer Networking: A Top-Down Approach, 8th edition.

Consider the 3-node packet-switched network:

A B C

Each link has a propagation delay of 5 and capacity of 1 Gbps. The packet processing time at each node is negligible, and only one message of 100,000 bytes is sent as 200 packets, each with a 500-byte payload and a 40-byte header.

(a) Calculate the per-hop transmission delay for a packet.

(b) When does C receive the first packet (completely)?

(c) When does C receive the second packet?

(d) When does C receive the entire message, i.e., all 100 packets?

(e) What is the throughput achieved for this communication?

(f) If throughput is less than the connection BW (which is the minimum of the BWs of the two links in the connection), then what are the reasons (pipeline delays, packet overhead, propagation delays, node processing, queueing delays, etc.) for the lower throughput? Give quantitative justifications: give the amount of BW lost for each cause.

(g) If the entire message is sent as one packet with a 40-byte header, when does C receive the message?

(h) What is the throughput now?

(i) Is the throughput of one-packet case higher or lower compared to the multi-packet case? Explain the result.