Problems: 1. Access technologies are classified into three categories. List the categories and give one example for each of them. (15 pts) 2. Suppose the following scenario. Users share a 4 Mbps link, and each user transmits continuously at 1 Mbps when transmitting, but cach user transmits only 20 percent of the time. When a circuit switching is used, how many users can be supported? (5 pts) 3. There are two types of wireless Internet access technologies. Compare and contrast them. (20 pts) 4. What are the five layers in the internet protocol stack? What are the responsibilities of theses layers? (30 pts) 5. How long does it take a packet of length 2,000 bytes to propagate over a link of distance 3000 km, propagation speed 2.7*10^8 m/s, and transmission rate 4 Mbps? More generally, how long does it take a packet of length L to propagate over a link of distance d. propagation speeds, and transmission rate R bps? Does this delay depend on packet length? Does this delay depend on transmission rate? (10 pts) 6. Consider the circuit-switched network in Figure 1.12. Recall that there are n circuits on cach link. (10 pts) HA E TOMTOM HA ube Figure 1.12. A simple were consisting of switches and fout links a) What is the maximum number of simultaneous connections that can be in progress at any one time in this network? b) Suppose that all connections are between the switch in the upper-left-hand corner and the switch in the lower-right-hand corner. What is the maximum number of simultaneous connections that can be in progress? 7. Consider the discussion in Section 1.3 of statistical multiplexing in which an example is provided with a 1Mbps link. Users are generating data at a rate of 100 kbps when busy but are busy generating data only with probability p = 0.1. Suppose that the 1 Mbps link is replaced by a 1 Gbps link. What is N, the maximum number of users that can be supported simultaneously under circuit switching? (10 pts)