1. What does the data link layer do

1. What does the data link layer do?
2. What is media access control, and
why is it important?
3. Under what conditions is media access
control unimportant?
4. Compare and contrast roll-call polling, hub
polling (or token passing), and contention.
5. Which is better, controlled access or
contention? Explain.
6. Define two fundamental types of errors.
7. Errors normally appear in , which is
when more than 1 data bit is changed by
the error-causing condition.
8. Is there any difference in the error rates of
lower-speed lines and higher-speed lines?
9. Briefly define noise.
10. Describe four types of noise. Which is likely to
pose the greatest problem to network managers?
11. How do amplifiers differ from repeaters?
12. What are three ways of reducing errors and
the types of noise they affect?
13. Describe three approaches to detecting
errors, including how they work, the probability of detecting an error, and any other
benefits or limitations.
14. Briefly describe how even parity and
odd parity work.
15. Briefly describe how checksum works.
16. How does CRC work?
17. How does forward error correction work? How is
it different from other error-correction methods?
18. Under what circumstances is forward
error correction desirable?
19. Compare and contrast stop-and-wait ARQ
and continuous ARQ.
20. Which is the simplest (least sophisticated)
protocol described in this chapter?
21. Describe the frame layouts for SDLC,
Ethernet, and PPP.
22. What is transmission efficiency?
23. How do information bits differ from
overhead bits?
24. Are stop bits necessary in asynchronous transmission? Explain by using a diagram.
25. During the 1990s, there was intense competition
between two technologies (10-Mbps Ethernet
and 16-Mbps token ring) for the LAN market.
Ethernet was promoted by a consortium of vendors, whereas token ring was primarily an IBM
product, even though it was standardized. Ethernet won, and no one talks about token ring
anymore. Token ring used a hub-polling–based
approach. Outline a number of reasons why
Ethernet might have won. Hint: The reasons
were both technical and business.
26. Under what conditions does a data link
layer protocol need an address?
27. Are large frame sizes better than small
frame sizes? Explain.
28. What media access control technique
does your class use?
29. Show how the word “HI” would be sent using
asynchronous transmission using even parity
(make assumptions about the bit patterns needed).
Show how it would be sent using Ethernet.