4.1 - Media Access Control

Question 1

The _______________ layer (Layer 2 of the OSI Model) is responsible for moving a message from one computer or network device to the next in the overall path from sender to receiver

Answer 1

data link layer

Question 2

A _______________ determines:
1. Media access
2. Message delineation
3. Error control

Answer 2

data link protocol

Question 3

Who can transmit at what time

Answer 3

Media access

Question 4

Where the message begins and ends

Answer 4

Message delineation

Question 5

How a receiver recognizes and correctes a transmission error

Answer 5

Error control

Question 6

The data link layer performs two main functions and therefore is often divided into two sublayers:

Answer 6

1. Logical Link Control (LLC)
2. Media Access Control (MAC)

Question 7

The data link layer’s connection to the network layer above it

Answer 7

Logical Link Control (LLC)

Question 8

Responsible for communicating with the network layer software (IP) and for taking the packet, surrounding it with data link PDU, to become a frame

Answer 8

Logical Link Control (LLC)

Question 9

Controls the physical hardware

Answer 9

Media Access Control (MAC)

Question 10

This software at the sending device controls how and when the physical layer converts bits into the physical symbols that are sent down the circuit; receiver does the opposite

Answer 10

Media Access Control (MAC)

Question 11

Refers to the need to control WHEN computers transmit

Answer 11

Media Access Control (MAC)

Question 12

_____________ becomes important when several computers share the same communication circuit (point-to-point, half-duplex configuration)

Answer 12

Media Access Control (MAC)

Question 13

1. Contention
2. Controlled access

Answer 13

Two approaches to media access control

Question 14

Computers wait until the circuit is free (no other computers are transmitting) and transmit whenever they have data to send

Answer 14

Contention

Question 15

With _____________, all nodes are operating in half-duplex (two-way traffic, but taking turns) mode, competing for the use of the medium

Answer 15

contention

Question 16

1. Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
2. Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)

Answer 16

Examples of contention

Question 17

Used on legacy bus-topology Ethernet

Answer 17

CSMA/CD

Question 18

Used on Wireless LANS

Answer 18

CSMA/CA

Question 19

One device controls the circuit and determines which clients can transmit at what time

Answer 19

Controlled

Question 20

Two commonly used controlled access techniques:

Answer 20

1. Access request
2. Polling

Question 21

Controlled access is a ____________ type of access — each node has its own time on the medium

Answer 21

deterministic

Question 22

Controlled access is used on legacy networks such as ____________ and __________

Answer 22

Token Ring… ARCNET

Question 23

This technique is similar to a situation in which the instructor calls on students who raise their hands

Answer 23

Controlled access

Question 24

With _______________ technique, client computers that want to send a request to transmit to the device controlling the circuit (e.g., wireless access point)

Answer 24

access request

Question 25

_______________ grants permission for one computer at a time. All other computers wait until that computer has finished

Answer 25

Controlling device

Question 26

The process of sending a signal to a client computer that gives it permission to transmit

Answer 26

Polling

Question 27

The client stores all messages that need to be transmitted

Answer 27

Polling

Question 28

Periodically, the controlling device (e.g., WAP) ______ the client to see if it has data to send

Answer 28

polls

Question 29

Types of Polling

Answer 29

1. Roll-call polling 2. Hub polling (Token Passing)

Question 30

The controller works consecutively through a list of clients until all are polled

Answer 30

Roll-call polling

Question 31

This type of polling can be modified to select clients in priority

Answer 31

Roll-call polling

Question 32

This type of polling involves some waiting time because the controlled has to poll a client and then wait for a response

Answer 32

Roll-call polling

Question 33

One device starts the poll and passes it to the next computer on the multipoint circuit, which sends its message and passes the poll (or token) to the next

Answer 33

Hub polling (Token Passing)