Chapter 6 - The Data Link Layer

Question 1

What are the Basic Services of This Layer?

Answer 1

• allows the upper layers to access the media using framing

- controls how data is placed onto the media and received from the media using media access control and error detection

Question 2

What is the Main Protocol on this Layer?

Answer 2

Ethernet

• 2 sub-layers
• Logical Link Control (LLC)
• Media Access Control (MAC)

Question 3

What Are the Transmission Methods?

Answer 3

• Half-Duplex

- Full-Duplex

Question 4

How Does the Data Transfer Occur?

Answer 4

1. a frame with addressing and error checking is created
2. router converts frame to the suitable type for WAN
3. router converts frame to the suitable type for LAN

Question 5

What are the Media Access Control Techniques?

Answer 5

• Contention Based: non-deterministic, low overhead, possibility of collisions, CSMA/CD and CSMA/CA
• Controlled: deterministic, high overhead, no collisions, token passing (token ring and FDDI)

Question 6

How Does CSMA/CA Operate?

Answer 6

1. Wait Interframe Space Period
2. Wait Contention Window Period
3. Transmission and Acknowledgement