The goal of this homework is to prepare you for the midterm exam. The questions
will be graded with scores of 2 (correct), 1 (partially correct), or 
0 (incorrect). The score of this homework will not count toward your final
grade.

HW is due in class on 09/23 (make sure you write your name and email address 
because I will email you the score). Solutions will be posted on the same
date.

1. What is a layered network architecture? What are the advantages and
   disadvantages of such architecture?

2. What advantages does a circuit-switched network have over a packet-switched
   network? What advantages does a packet-switched network have over a
   circuit-switched network?

3. How are virtual connections identified in ATM? What are the advantages of
   this type of identification?

4. Two hosts agree to use the CRC polynomial x^5 + x + 1 to detect bit errors.
   Assume the receiver gets this message: 110101110010. Does the receiver
   detect an error in this message? Show all work.

5. Why do we need sliding window protocols? How do they work?