We are sending a 20 Mbit MP3 file from a source host Sto a destination host D. All links in the path between source and destination have a transmission rate of 10 Mbps, unless otherwise noted. Assume that the propagation speed is 2x108 meters/sec, and the distance between source and destination is 100,000 km. The following questions (1-3) refer to this setup (A). Now suppose there are two links between source and destination, with one router connecting the two links. Each link is 50,000 km long. Again suppose the MP3 file is sent as one packet. Suppose there is no congestion, so that the packet is transmitted onto the second link as soon as the router receives the entire packet. The following questions (d-f) refer to this setup (B).
A. The end-to-end delay (defined again as from the time S starts transmitting the first bit, until D receives the last bit of the MP3 file) is:
B. Assume again two links with the previous parameters (Problem B), but now suppose that the MP3 file is broken into 2 packets, each of 10 Mbits. Ignore headers that may be added to these packets. Also ignore router processing delays. Assume store and forward packet switching at the router. The total delay is:
C. Consider again two links between S and D and the rest of the setup of Problem B. Also assume negligible packet headers (i. e., H=0 bits is added to every packet). What is the optimal number of packets to breakdown the MP3 file so as to minimize the end-to-end delay?