CS158a Spring 2011Practice Midterm

To study for the midterm I would suggest you: (1) Know how to do (by heart) all the practice problems. (2) Go over your notes at least three times. Second and third time try to see how much you can remember from the first time. (3) Go over the homework problems. (4) Try to create your own problems similar to the ones I have given and solve them. (5) Skim the relevant sections from the book. (6) If you want to study in groups, at this point you are ready to quiz each other. The practice midterm is below. Here are some facts about the actual midterm: (a) It is closed book, closed notes. Nothing will be permitted on your desk except your pen (pencil) and test. (b) You should bring photo ID. (c) There will be more than one version of the test. Each version will be of comparable difficulty. (d) One problem (less typos) on the actual test will be from the practice test.

1. Briefly define the notions of packet switched network and circuit switched network; STDM and FDM.
2. Give the seven layers of the OSI model together with a short explanation of the role of each layer.
3. Give the Java code needed to open a socket connection to port 1234 of somewhere.com, get a reader for the appropriate input stream and get one line from this reader.
4. How many bytes could be in transit is a 100Mbps link with a 25ms latency? Give the Linux command to take down the 0th Ethernet interface.
5. Briefly describe Manchester Encoding, 4B/5B encoding, what a PPP frame looks like.
6. Suppose we are computing a CRC-15 of 1KB of data using the generating polynomial x¹⁵+ x¹⁴+1. Based on what we learned in class what kinds of errors would we be able to detect?
7. Describe how the Sliding Window ARQ algorithm works.
8. How can one do a broadcast in Ethernet? What is 1-persistence? Describe how a sender knows a packet has arrived in a token ring.
9. Imagine we have 6 bridges connected in a ring. Suppose their addresses are 1, 2, 3, 4, 5, 6. Explain the sequence of messages that would be communicated according to the spanning tree algorithm for these bridges to compute a spanning tree amongst themselves.
10. Give two different ways frame synchronization can be done in ATM. What is a self-routing fabric?