Chapter 5.

Question 1

How did 8.2.11b radios achieve faster radio transmission rates?

Answer 1

By using spreading/coding techniques called CCK or complementary code keying. A modulation method using the phase properties of the RF signal.

It used a spread tech called Barker code. Resulting in 1,2,5.5, and 11 Mbps.

Question 2

Is FHSP and DSSS backward compatible with each other?

Answer 2

Depends. Because the 802.11b amendment specified the use of only a DSSS-type physical medium and did not specify FHSS.

Specifically many manufacturers used different interpretations of the amendment, since there was no WiFi alliance at the time. So, it could or couldn’t work.

Question 3

The IEEE specifically define 802.11 technologies at what 2 layers?

Answer 3

The physical layer and the MAC sublayer of the data-link layer.

Question 4

The WMM is a mirror of what 802.11 standard?

Answer 4

The 802.11e

Question 5

VoWiFi requires a handoff of how long to avoid degradation of voice?

Answer 5

100 milliseconds.

Question 6

What 2 wireless frames are country code information stored in?

Answer 6

Beacons and Probe Responses.

Question 7

What are the 3 main components of security in the original 802.11 standard?

Answer 7

Data Privacy, (Encryption, Data integrity (Protection from modification), and authentication (identity verification).

Question 8

What are the 5 things an AP can do to remain DFS compliant?

Answer 8

AP can quiet a channel to test for the presence of radar.
An AP may test a channel for the presence of radar before using the channel.
An AP can detect radar on the current channel and other channels
An AP can cease operations after radar detection to avoid interference.
An AP once radar is detected may choose a different channel to transmit on and inform all the associated stations.

Question 9

What did the 802.11af amendment do? Explain this technology, and some things it can do.

Answer 9

Allows the use of wireless in the newly opened TV white space frequencies between 54 and 790 MHz.

Uses spectrum in regulatory domains that are not given to TV stations. Will use a built in GPS to locate itself and figure out which TV stations are NOT broadcasting in that area then use those.

Channel width is 6 MHz and 8 MHz and up to 4 channels can be bonded together.

Can support up to 4 spatial streams. Using 4 channels and 4 spatial streams can have data rate of up to 426-568 Mbps.

Wall penetration will be better.

Question 10

What did the 802.11i amendment bring to the table in terms of authentication?

Answer 10

Two methods. PSK or preshared keys or EAP (extensible authentication protocol)

Question 11

What did the 802.11i amendment bring to the table in terms of data integrity? What was included in the header.

Answer 11

CCMP uses an integrity checker called MIC or Message Integrity Check. The trailer of all 802.11 frames are a 32 bit CRC value called a frame check sequence which protects the entire frame.

Question 12

What did the 802.11i amendment bring to the table in terms of data privacy?

Answer 12

Used a stronger encryption method called Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (CCMP).

Question 13

What did the 802.11i amendment do?

Answer 13

The 802.11i amendment, which was ratified and published as IEEE Std 802.11i-2004, defined stronger encryption and better authentication methods. The 802.11i amendment defined a robust security network (RSN).

Question 14

What does data rate mean? How does this compare to throughput and why?

Answer 14

A data rate is the number of bits per second the Physical layer carries during a single-frame transmission, normally stated as a number of millions of bits per second (Mbps).

Throughput is about half of that of data rate do to medium contention and access methods.

Question 15

What does it mean to be spread spectrum? What clause was this known for?

Answer 15

Spread spectrum means that bandwidth is wider that what is required to carry the data.

This was known by clause 14

Question 16

What does it mean when an 802.11 G AP is in B/G Mode? Why can this mode suffer in performance?

Answer 16

This is the default state, called Mixed Mode. Support for older legacy devices are enabled.

However, if an older phy client is detected the AP issues a protection mode order to all clients. This Can drop the throughput from 54 Mbps to 20-8 Mbps.

Question 17

What does it mean when an 802.11G AP is in B-Only mode?

Answer 17

The access point turns into a B mode only AP, allowing support for legacy devices using DSS, HR-DSSS and ERP-DSSS/CCK tech.

Question 18

What does it mean when an 802.11G AP is in G-Only Mode?

Answer 18

Support for older legacy devices are turned off. Only ERP-OFDM tech is used.

Question 19

What does the 802.11y amendment do?

Answer 19

Allowed devices to operate in both the licensed and unlicensed spectrums. This means that content-based protocol mechanisms are needed to avoid interference between devices. To accommodate this, DSE (Dynamic STA enabled), was used which forces 802.11 radios broadcast their actual location as a unique identifier in order to help resolve interference with non 802.11 radios in the same frequency.

Question 20

What does the transmit power control (TPC) service provide for the following?

Answer 20

Client stations can associate with an AP based on their transmit power.
Designation of the maximum transmit power levels permitted on a channel, as permitted by regulations.
An AP can specify the transmit power of any or all stations that are associated with the AP.
An AP can change transmission power on stations based on factors of the physical RF environment such as path loss.

Question 21

What is a mesh access point?

Answer 21

A device that provides both mesh functionalities and AP functionality at the same time.

Question 22

What is a mesh point portal?

Answer 22

A device that acts as a gateway to one or more external networks such as an 802.3 wired backbone.

Question 23

What is a mesh point?

Answer 23

A mesh point (MP) is capable of using a mandatory mesh routing protocol called Hybrid Wireless Mesh Protocol (HWMP) that uses a default path selection metric.

Question 24

What is an 802.11 Study Group?

Answer 24

They are in charge of investigating the possibility of putting new features and capabilities into the 802.11 standard.

Question 25

What is CCK?

Answer 25

CCK or complementary code keying. A modulation method using the phase properties of the RF signal.

Question 26

What is DSSS? What clause was this known by?

Answer 26

Direct Sequence Spread Spectrum, another spread spectrum tech that uses fixed channels.

It used clause 16.

Question 27

What is robust management frames? What are action frames? What is used with unicast?

Answer 27

Management frames can be protected by the management frame protection service and include disassociation, deauthentication, and robust action frames.

Action frames are used to request a station to take action on behalf of another station, and not all action frames are robust.

CCMP is used for unicast.

Broadcast and multicast frames are protected using Broadcast/multicast integrity protocol. This is encrypted using AES-128.

Question 28

What is the difference between OFDM and ERP-OFDM?

Answer 28

The only difference is transmit frequency. OFDM refers to 802.11a devices that transmit in the U-NII-1, U-NII-2, and U-NII-3 bands. ERP-OFDM refers to 802.11g devices in the ISM band.

Question 29

What is the goal of 802.11G protection mechanisms?

Answer 29

To prevent older 802.11b HR-DSSS or 802.11 DSSS radio cards from transmitting at the same time as 802.11g radios.

Question 30

What massive improvements did 802.11ac-2013 bring? What frequency does it operate in?

Answer 30

The 802.11ac-2013 amendment defines Very High Throughput (VHT) enhancements below 6 GHz.

Operates only in 5 GHz.

Wide channels : Can have 40, 80, or 160 MHz wide channels.

New Modulation : Provides 256 QAM modulation, which has the potential to provide a 30% increase in speed. Requires very high signal to noise.

Spatial streams : Can have up to 8 spatial streams.

Improved MIMO and Beamforming. Created MU-MIMO which allows an AP to communicate with more than 1 client at a time.

Question 31

What the purpose behind 802.11p?

Answer 31

To define enhancements to the 802.11 standard to support Intelligent Transportation Systems, applications. Communication between roadside infrastructure is supported. This was designed for vehicle communication between roadside infrastructure.

Question 32

What type of frame is DFS and TPC information located?

Answer 32

Inside of management frames.

Question 33

What was the 802.11r known for? How did it solve the speed issue with authentication while roaming?

Answer 33

Creating Fast Roaming. Used for VoIP and WMM.

To establish a QoS stream and set up a security association with a new access point in an efficient manner that allows bypassing
802.1X authentication when roaming to a new access point. The client station is able to achieve these tasks either over the wire via the original access point or through the air. Eventually, the client station will complete the roaming process and move to the new
access point.

Question 34

What was the benefits of the 802.11n amendment?

Answer 34

To increase throughput of both the 2.4 GHz and the 5.0 GHz bands.
Amendment defined a new standard called HT or high throughput which provides PHY and MAC enhancements to support data rates of up to 600 MBps.
MIMO tech in unison with OFDM. Used multiple send and receive antenna and capitalized the effects of multipath.

Question 35

What was the main goal of G and the task group assigned to it? What was the 2 mandatory phy layers and 2 optional techs?

Answer 35

To achieve higher data rates and remain compatible with the 802.11 MAC.

2 mandatory are ERP-OFDM and ERP-DSSS/CCK

Optional was ERP-PBCC and DSSS-ODFM

Question 36

What was the name of the 5 GHz band that originally was created in 1999 amendment? How many channels where available? What was the name of the 3 sub bands?

Answer 36

U-NII.
12 channels where available.

U-N11-1, U-N11-2, U-N11-3

Question 37

What was the original 802.11d-2001 amendment?

Answer 37

Because the original specifications only had the compliance and regulatory domains of US, Japan, Canada and Europe. The amendment allowed 802.11 WLAN to operate in areas not served by the original standard.

Question 38

What was the PHY created with 802.11 G that allowed it to be backward compatible with b networks?

Answer 38

A phy tech called Extended Rate Physical DSSS was used to support data rates of 1 2 5.5 and 11.

Question 39

What was the PHY used in G to achieve higher data rates? What where those rates?

Answer 39

The PHY ERP-OFDM was used with G. 6 9 12 18 24 36 48 54

Question 40

What was the primary goal of 802.11j?

Answer 40

Obtain japanese regulatory approval by enhancing the 802.11 MAC and 802.11a PHY to operate in Japanese 4.9 and 5 GHz bands.

Question 41

What was the primary purpose of 802.11e?
What did it do?
What methods can an 802.11 radio use to gain control of the half-duplex medium?
Default mode and the new enhanced mode?

Answer 41

To enhance QOS for Voice and other media applications.

The 802.11e amendment defines the layer 2 MAC methods needed to meet the QOS requirements for time-sensitive applications over IEEE 802.11 WLANS.

The default method used to control the medium was called DCF or distributed coordination function, is a contention based method determining who gets to transmit on the wireless medium next.

The 802.11e amendment defines enhanced medium access methods to support QoS
requirements. Hybrid Coordination Function (HCF) is an additional coordination function that is applied in an 802.11e QoS wireless network. HCF has two access mechanisms to provide QoS. Enhanced Distributed Channel Access (EDCA) is an extension to DCF.
The EDCA medium access method will provide for the “prioritization of frames” based on upper-layer protocols. Application traffic, such as voice or video, will be transmitted in a timely fashion on the 802.11 wireless medium, meeting the necessary latency requirements.

Question 42

What was the purpose behind 802.11ae amendment? What was its primary goal?

Answer 42

Specifies enhancements to QoS management. A quality of service management frame service can be enabled, allowing some of the management frames to be transmitted using a QoS access category that is different that the access category that is assigned to voice traffic.

To improve the quality of service of other streams.

Question 43

What was the purpose behind 802.11s?

Answer 43

Access points can act as portable devices to a wireless distribution system. The 802.11s amendment proposes the use of a protocol for adaptive, auto configuring systems that support broadcast, multicast, and unicast traffic over a multihop mesh WDS. They improved the MAC/PHY layers to handle this.

Created a new networking routing protocol called Hybrid Wireless Mesh Protocol that uses a default path selection metric. These were created from Mesh Points. Created a mesh network, that created a wireless network between access points and didn’t need 802.3 access.

Question 44

What was the purpose behind 802.11v? What did it create, what is it used for, how did it work.

Answer 44

Defines methods of retrieving information from client stations.
Eases the configuration of client stations wirelessly from a central point of management.

This created WNM (Wireless network Management), which gives stations the ability to exchange info for the purpose of improving the performance of the overall wireless network.

Access points and client stations use WNM protocols to exchange operational data so that each station is aware of the network conditions, allowing stations to be more cognizant of the topology and state of the network.

Also provides support for the multiple BSSID capability, and offer a new WNM sleep mode in which a client station can sleep for long periods of time without receiving frames from the AP.

Question 45

What was the purpose behind the 802.11aa? What did it improve?

Answer 45

Specifies QoS enhancements to the 802.11 Media Access Control (MAC) for robust audio and video streaming for both consumer and enterprise applications.

Provides improved management, increased link reliability, and increased application performance.

Question 46

What was the purpose of 802.11h? What else did it do?

Answer 46

Amendment defines mechanisms for DFS or dynamic frequency selection and transmit power control. It was originally used to satisfy regulatory requirements in Europe and to detect and avoid radar. Insured that radio transmissions will not cause interference with 5 GHz satellite and radar transmissions.

It created the U-NII-Extended band. This created 11 more channels. Radar detection is required on all U-NII2 and U-NII-2 Extended Bands.

Question 47

What was the purpose of 802.11k?
What does it call for?
What was it required to report on?
How does a client request before roaming using this tech?

Answer 47

To provide a means of radio resource measurement (RRM).
The amendment calls for measurable client statistical information in the form of requests and reports for the physical layer 1 and the MAC sublayer of the data-link layer2.

Physical layer information - SNR, Signal strength, data rates. MAC info such as frame transmissions, retries and errors.

Channel statistics - Clients may gather noise floor info based on any RF energy in the background of the channel and report this info back to the AP. Channel load info as well.

Neighbor Reports - 802.11k gives client stations the ability to learn from access points or controllers about other access points and where the client stations might potentially roam.

The client station asks for a neighbor report detailing available access points from best to worst. Before a station roams, it will request the neighbor report from the current AP or controller and then decide whether to roam to one of the access points on the neighbor report. The client can now make a better roaming decision.

Question 48

What was the purpose of 802.11w?

Answer 48

To prevent deauth attacks. It was common for a DoS attack on layer 2 to take out a wireless network. Layer 2 management frames where spoofed and send back to the AP, deauthing it and all its clients. The 802.11w amendment provides protection for unicast, broadcast, and multicast management frames. They used robust management frames.

Question 49

What was the purpose of 802.11z?

Answer 49

To establish and standardize Direct Link Setup (DLS) mechanism to allow operation with non DLS capable access points.

Most WLAN has client stations that are associated to the same access point must pass through the access point. DLS allows client stations to bypass the access point and communicate with direct frame exchanges.

Question 50

What was the purpose of the 802.11u? What was it the basis for?

Answer 50

To address interworking issues between an IEEE 802.11 access network and any external network to which it is connected.

Defines functions and procedures for aiding network discovery and selection by STA’s, information transfer from external networks using QoS mapping, and a general mechanism for provision of emergency services.

Was the basic for Hotspot 2.0

Question 51

What was the reason behind 802.11ad-2012? What are the pros and cons? What else did this create to enhance security?

Answer 51

This is a new amendment that defines Very High Throughput (VHT) enhancements using the much higher unlicensed frequency band of 60 GHz.

Can have throughput as high as 7 Gbps. Downsize is the effective distance. Line of site only.

It also created a new encryption mechanism because CCMP was to slow to handle this kind of data rate. Created a new encryption called Galois/Counter Mode Protocol, GCMP which also uses AES cryptography.

Question 52

What was the required supported data rates of wireless A?

Answer 52

6 12 24 and 54

Question 53

What was the spread tech called that generated data rates of 5.5 and 11

Answer 53

HR-DSSS

Question 54

When the 5GHz band started becoming crowed the FCC opened up more of the 5GHz frequency band. The IEEE created an amendment that utilized this….called what?

Answer 54

The 802.11h amendment.