1. Suppose that Bob sends 172,800 bits to Alice over a 5.76 Kbps link (note, 1 Kbps = 103 bps) that uses circuit switching. Suppose that circuit switching on the link is implemented using TDM, that a frame is 1 sec, and that a frame consists of 12 slots. Bob is assigned one slot in every frame. How many minutes does it take Bob to transmit all bits to Alice? (6 points)

2. Suppose that Router A and Router B are connected via a 2 Mbps link (note, 1 Mbps = 106 bps), and that the link connecting the two routers has a length of 44 meters. Suppose that Router A is transmitting a packet, and that there are 8 additional packets in the queue of the router, when a new packet arrives at Router A. Assume the following.
   1. Every packet consists of 10,000 bits, and that 6000 bits of the currently-being-transmitted packet has been transmitted by Router A when the new packet arrives.
   2. Propagation speed of a bit over the link connecting the two routers is 2 x 103 meters/sec.
   3. Processing delay of a (whole) packet at a router takes 1 millisecond (i.e., 0.001 seconds).

What is the total delay of the new packet in arriving at Router B, i.e., how long does it take the new packet to arrive at Router B from the time it arrived at Router A? In your solution, clearly identify all four delay components the new packet experiences. (10 points)

3. What are the five layers in the Internet protocol stack? Explain also in your own words the principal responsibilities of each of the five layers.

(10 points