Chapter 9

Question 1

Packets?

Answer 1

Data Units at the Network Layer

Question 2

Frames?

Answer 2

Data Units at the Data Link Layer

Question 3

Bits?

Answer 3

Binary Digits

Question 4

Data Link Layer?

Answer 4

DLL has two sublayers
Logical Link Control (LLC)
and
Media Access Control (MAC)

Question 5

Logical Link Control?

Answer 5

Establishing Flow Control

Maintains Flow Control

Question 6

Media Access Control (MAC)

Answer 6

802.11 Specified Operations

Where the MAC address resides

Question 7

What is MSDU?

Answer 7

MAC Service Data Unit

- Data portion of MAC coming from LLC

Question 8

What is MPDU?

Answer 8

MAC Protocol Data Unit

- After encapsulation in MAC frame

Question 9

Detailed MSDU?

Answer 9

Contains Data From Layers 3-7 and the LLC
The Data Payload
Only Data Frames Carry the MSDU
Maximum size of 2,304 bytes

Question 10

Detailed MPDU?

Answer 10

Mac Protocol Data Unit
Encapsulates the MSDU
Is an 802.11 Frame

Question 11

Physical Layer?

Answer 11

Has two Sub-Layers

• Physical Layer Convergence Protocol (PLCP)
• Physical Media Dependent (PMD)

PLCP Services Data Unit (PSDU)
PLCP Protocol Data Unit (PPDU)

Question 12

PLCP Data Units?

Answer 12

PLCP Services Data Unit
- The same frame as the MPDU
PLCP Protocol Data Unit (PPDU)
- Adds Preamble and PHY Header

Question 13

802.11 and 802.3 Interoperability

Answer 13

802. 3 Frames are encapsulated within 802.11 frames for Transmisision
803. 3 Standard frame Max Size = 1518 bytes
804. 11 standard frame Max Size = 2347 bytes
805. 11 has four addresses field in header

Question 14

Possible addresses of 802.11 and 802.3

Answer 14

Receiver Address (RA)
Transmitter Address (TA)
Basic Service Set Identifier (BSSID)
Destination Address (DA)
Source Address (SA)

Question 15

802.11 Frames

Answer 15

Frame Types

• Management Frame
• Control Frame
• Data Frame

Question 16

Management Frames?

Answer 16

Association request and response.
Reassociation request and response
Probe request, and response
Beacon
ATIM
Disassociation
Authentication, and Deauthentication
Action
Action No ACK
Timing advertisement

Question 17

Beacon Frame Content?

Answer 17

Time Stamp
Parameter Sets
Channel Information
Data Rates
BSS Capabilities
SSID
TIM and DTIM
QoS Capabilities
Security Capabilities
Vendor Proprietary Information

Question 18

What is Passive Scanning?

Answer 18

Passive Scanning Stations Listen for Beacon Frames

Question 19

What is Active Scanning?

Answer 19

Active Scanning Stations use probe request and response frames

Question 20

Authentication?

Answer 20

Stations must authenticate to begin connection with an AP
Failed authentication is the #1 Cause of Failed Association
Many authentication methods exist:
- Open (no credentials required)
- Shared key (uses WEP key_

Question 21

Association?

Answer 21

Occurs AFTER authentication
Requires Mutually Supported Functions
Once Associated, Stations can contend for the Medium and Pass Data onto the network

Question 22

States of Authentication and Association?

Answer 22

State 1:
Unauthenticated
Unassociated.

State 2:
Authenticated
Unassociated

Stage 3:
Authenticated
Associated

Question 23

State 1 Contains?

Answer 23

1. Listen to Beacons
2. Probe Request
3. Probe Response
4. Authentication Request
5. Authentication Response

Question 24

State 2 Contains?

Answer 24

6. Association Request

7. Association Response

Question 25

State 3 Contains?

Answer 25

8. (Optional: EAPOL Authentication) 9. (Optional: Ecrypt Data) 10. Move user data

Question 26

Basic and Supported Data Rates?

Answer 26

Basic Rates are the MANDITORY data rates of the BSS Supported Rates are the OPTIONAL data rates of the BSS Information is Found in the beacon management frame

Question 27

Control Frame?

Answer 27

``` Power Save Poll Request To Send Clear to Send Acknowledgment (ACK) Contention Free-End CF-End + CF-ACK Block ACK Request Block ACK Control Wrapper ```

Question 28

ACK Frame?

Answer 28

Acknowledgement Frame Every unicast frame bu the Standard should be acknowledged Used due to Inability to Detect Collisions Provide Delivery Verification

Question 29

Protection Mechanism?

Answer 29

``` Request to Send / Clear to Send Clear to Send to Self Help Combat Hidden Node Issues Allows Mixed Mode Operations Creates Additional Overhead Frames Sent at Lowest Basic Rate ```

Question 30

Clear to Send to Self

Answer 30

``` Less overhead than RTS/CTS From the station to itself Used in Mixed Mode BSS Operations Creates Additional Overhead Frames Sent at Lowest Basic Rate ```

Question 31

Data Frames?

Answer 31

Can be Pure Data Can be Null Data Can be combined with other functions Contains the MSDU

Question 32

Power Management?

Answer 32

``` Conserves Battery Life Require use of TIM, DTIM, or ATIM Two Modes Used - Active Mode (Always ON) - Power Save Mode (ON and OFF) Legacy Power Save Still Used WMM-PS Used on Newer Devices ```