CMPE 401 - Computer Interfacing

Assignment #3

1. In your own words, briefly explain what is meant by "busy waiting" and "interrupt-driven" synchronization of data transfers. What are the major advantages and disadvantages of each method compared to one another?

2. On slide 7-13 of the lecture notes, the transport layer peer entities in the two systems are shown interacting directly using the Layer 4 Protocol. In contrast, the network layer entities in the two systems are shown interacting with an intermediate box labelled "Communication Network" according to the Layer 3 protocol. What is this diagram illustrating by showing the Layers 3 and 4 in these different ways?

3. In your own words, briefly explain how routers and bridges are used to join up subnetworks into larger data networks. Be sure to clearly explain the difference between routers and bridges.

4. Hubs are often preferred to connect a small number of nodes together into a subnet. Separate 10BASE-T twisted pair cables are used to connect each node to the hub. This is a different topology from the original Ethernet standard, which envisaged all nodes in a subnet being connected together over a shared 10BASE5 coaxial cable. Why is the hubbed or star topology generally preferred over the original Ethernet topology?

5. Briefly describe the different between the User Datagram Protocol (UDP) and the Transmission Control Protocol (TCP). Using resources on the Internet or other references, determine four application-level protocols that are most commonly run over UDP. In each case, briefly justify why each of those four upper layer protocols uses UDP as opposed to TCP.

6. In a client-server interaction, the port numbers on the servers are usually standardized (e.g. HTTP uses port 80 on the server) whereas the port numbers on the clients can be assigned more freely to any unused port numbers. Briefly explain why the server port numbers are standardized in this way.

7. Some application-level protocols (e.g. FTP) use separate TCP connections to communicate control information and control/status information, whereas other protocols (e.g. TELNET) use a single channel for both data and control/status information. In your own words briefly describe important advantages and disadvantages of these two methods?