Problem 1: Consider figure 1, where the sender transmits one packet of size L = 1 KB (kilobytes). The link speed are R1 = R2 = R3 = 1 Mbps (megabits per second). The length of each link is 100 Km. Compute the end-to-end delay for the following situations. We assume that the propagation speed of the packet is 20,000 Km/s, and that the processing time of the packet at each router is 5 s.

(a) Both routers are store-and-forward routers.

(b) Both routers are cut-through routers. Note that a cut-through router does not wait for the entire packet to arrive before it starts the transmission of the packet. (Remark: In reality, there are cut- through switches instead of cut-through routers. But, for this problem, we assume there are cut- through routers.)

(c) Suppose R1 = R2 = R3 = 1 Gbps (gigabits per second). Repeat part (a) and (b).

(d) Again repeat part (a) and (b). However, now, R1 = R2 = 2 Mbps, and R3 = 1 Mbps. Three packets of the same length, each with L = 1KB, are transmitted at the sender. What is the end-to-end delay of each packet? For simplicity, you may neglect the processing time, which is small compare with other delays. Also, you need not count packets waiting time at the sender.

(e) For the situation in (d), draw a timing diagram by completing figure 2 and identify the queueing delay of each packet. Again, you may neglect the processing time.

RI R2 R3 Sender Router 1 Router 2 Receiver Figure 1 0) 0 2, 4 2, 2 4 packet 1 4 packet 2 10 10 10- time (ms) Figure 2. Timing diagram