End-to-end delay for A to deliver two packets (sent back-to-back) in a packet-switched network to B Each packet is 50 kbits long Queue at R is initially empty Suppose that we put another router R2 in the middle of R-B link, thus forming two routers in the middle (R1, R2), with three links from the sender A to the receiver B. The newly added link R2-B is identical to the original A-R link (now called A-R1 link), with the same link speed of 10Mbps and propagation delay of 10ms. Instead, the middle link R1-R2 is slow, running at 1Mbps, with propagation delay of 90ms. The sender A has 3 packets to transmit to B, each of which is 50kbits. Assume that the queues at each of the routers R1 and R2 are all empty initially and ignore any processing delay at R1 and R2. Assume that A starts transmitting 3 packets back to back at t = 0, when does the first packet arrive to B? a) When does the last 3^rd packet arrive to B (i.e., the total end-to-end delay to transmit all 3 packets back to back to the destination B)? b) Compute the total queueing delay (sum of queueing delays over the path from A to B) for each of the three packets. c) What is the average queueing delay (out of 3 packets)? You need to show clearly all your steps. Suppose that the sender A decides to transmit 3 packets not back-to-back, but with some 'spacing' in the middle. In other words, A starts transmitting packet l at t = 0, and once A is done transmitting packet 1, A goes idle, waiting for s seconds, and then start transmitting packet 2 at t = mu + s, where mu is the transmission delay of one packet over the link A-R1. Similarly, there is s-seconds spacing between packet 2 and packet 3. a) What is the minimum value of s such that none of the packets will suffer any queueing delay in the middle? b) Do you think the sender A in reality can find such spacing so that packets won't have to wait in the queue? Here assume there is no other protocol running between A and B (i.e., take the scenario 'as is', or assume UDP is running end-to-end). Carefully write down your logics