Sample Questions for the Final Exam

The final examination for CS460 is comprehensive. That is, you are responsible for knowing all of the information covered during the semester (including lectures, readings, and assignments). The final examination will focus on concepts, but you will be responsible for knowing various important facts as well.

1. Answer the Sample Questions for Exam 1.
2. Answer the Sample Questions for Exam 2.
3. Answer the questions from homeworks 8, 9 and 10.
4. Answer the questions from chapters 5, 6 and 8 in the textbook.
5. Choose the best answer to each of the following:

   (1)	_____	A channel is:
   		A logical path for a "conversation" A frequency band/time slot/wavelength allocated to a "conversation" Both of the above Neither of the above
   (2)	_____	Radio waves are in the:
   		Gamma ray band Electromagnetic spectrum Both of the above Neither of the above
   (3)	_____	Frequency is normally measured in:
   		Hertz Volts Wires Amps
   (4)	_____	A digital transmission consists of:
   		A continuously varying waveform A string and two cups Both of the above Neither of the above
   (5)	_____	Bluetooth uses the 2.4GHz band because:
   		Bluetooth supports connection-oriented links Bluetooth uses 2400 channels The 2.4GHz band is unregulated The 2.4GHz band is blue-shifted None of the above
   (6)	_____	Symmetric key encryption involves:
   		Two keys, one triangular and one rectangular Two keys, one numeric and one alphanumeric A single key for encryption and decryption All of the above None of the above
   (7)	_____	Creation of a digital signature involves:
   		A message A message digest A public key encryption algorithm All of the above None of the above
   (8)	_____	VeriSign is an example of:
   		A hypertext transfer protocol (HTTP) provider A certification authority (CA) A manufacturer of Dynamic Host Configuration Protocol (DHCP hardware All of the above None of the above
   (9)	_____	Transport Layer Security (TLS) makes use of:
   		Symmetric key encryption Public key encryption Both of the above Neither of the above
   (10)	_____	In IPsec, a session is defined by:
   		An IP address A protocol A port All of the above None of the above
6. Carefully define each of the following terms (as we have used them in this course):

   Infrsatructure Network

   Piconet

   Wavelength
7. At what layer (assuming a 5-layer view) do each of the following typically operate?

   Ethernet

   IP

   TCP

   SMTP
8. Identify two common guided media used for data communications.
9. Identify two advantages or two disadvantages of satellite communications. (Note: Do NOT identify one advantage and one disadvantage.)
10. Explain what one means when one says that Ethernet uses Manchester encoding.
11. Describe (in detail) the Carrier Sense Multiple Access/Collision Detection (CSMA/CD) process.
12. Explain why Wi-Fi uses Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) rather than CSMA/CD. Be specific.
13. Explain why Wi-Fi uses virtual carrier sensing (rather than direct carrier sensing).
14. Bluetooth uses a 1-bit sequence number. Write an expression for calculating the "next" sequence number from the the "previous" sequence number. You must NOT use an if statement or the conditional operator.
15. Explain the differences between unicast, broadcast, and multicast.
16. Explain why the need for acknowledgements makes it difficult to make a broadcast/multicast protocol reliable.
17. What is IP tunneling? How can it be used to support Mobile IP?
18. Explain the difference between symmetric key encryption and public key encryption. How does this relate to functions that can and can't be easily inverted?
19. Explain what happens (and why) if there is interference on the transmission medium when a digitally signed message is transmitted. You must assume that there is no error detection/correction.
20. Explain why Ethernet frames have a MAC address and not an IP address.
21. Explain how public key encryption and/or symmetric key encryption could be used to improve the confidentiality of a network file service.
22. Explain how public key encryption and/or symmetric key encryption could be used to improve the confidentiality of a directory service (like LDAP).
23. Consider the Domain Name System (DNS).
    1. Why should the DNS be considered an application layer protocol?
    2. Does the DNS require reliable communications? Why or why not?
    3. How might an attacker "interfere with" the DNS?
24. Explain the differences between IPsec and Transport Layer Security (TLS) focusing on the difference between connectionless and connection-oriented services. How do these differences relate to the concept of handshaking (as we have used the term this semester)?
25. Explain how the topology of a network impacts the need for encryption. Does the topology of a network have an impact on the relative advantages/disadvantages of symmetric/public key encryption? Explain how the communications medium impacts the need for encryption. Does the communications medium have an impact on the relative advantages/disadvantages of symmetric/public key encryption?
26. Given the nature of Bluetooth and your answers to the questions above, design a security system for Bluetooth.
27. Human-readable messaging systems (email, instant messaging, text messaging) provide very different services from peer-to-peer file sharing systems. Yet, the designers of such systems must deal with (at least) one similar "problem". Discuss this "problem" and the different options available to solve it.
28. Most implementations of the Lightweight Directory Access Protocol (LDAP) serve reads more efficiently than writes. Why would this make it inappropriate for an instant messaging directory?