Final Exam -- open book section -- 14 December

Problem 1. (5 points)

Exactly how many class A, B, and C networks can exist? Exactly how many hosts can a network in each class have? Be careful to allow for broadcast as well as class D and E addresses.

[This is exercise 4.1 on page 71 of the text.]

Problem 2. (5 points)

Consider a machine with two physical network connections and two IP addresses I1 and I2. Is it possible for that machine to receive a datagram destined for I2 over the network with address I1. Draw a diagram to explain your answer.

[This is based on exercise 8.4 on page 120 of the text.]

Problem 3. (6 points)

The following ping commands all refer to non-exist machine names or IP numbers:

For each command, where, if anywhere, is it discovered that the target machine does not exist?

Problem 4. (5 points)

If the CSCI department replaced our bridge with a router, what changes would we have to make in our workstations?

Problem 5. (2 points)

What serious mistake is being made by the programmer that wrote the following three successive lines of code? Assume that betnum is correctly declared as an integer.

     write(1, "What number are you betting on?\n", 32) ;
     scanf("%d", &betnum) ;
     printf("Bet placed on %d\n", betnum) ;

Problem 6. (3 points)

Where in the textbook is

discussed? What does this strange symbol mean?

Problem 7. (10 points)

In Homework 13, you wrote an application that sent UDP packets to port 8888 of penrose.cs.unca.edu. Let's assume you were running your application on the machine enka.cs.unca.edu. In the space below draw one of the packets that was sent between enka and penrose. Show the fields of all the relevant protocol headers, but don't worry about the specific values of the fields. For example, it is acceptable to label a field as "IP address of enka" or "protocol number for ICMP."

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