1.
Each of the following protocols is supported on an IEEE 802.11 network except a.
System Network Architecture (SNA) b.
TCP/IP c.
Appletalk d.
IPX/SPX
2.
_____ is a group of wireless devices that is served by a single access point (AP). a.
Basic Service Set b.
ad hoc mode c.
Extended Service Set d.
Independent Service Set
3.
Each WLAN must be assigned a unique identifier known as the _____. a.
Service Set Identifier (SSID) b.
Access Category Channel c.
Traffic Indication Set (TIS) d.
Beacon identifier
4.
With dynamic rate shifting implemented in a WLAN, what happens when a user moves farther away from the access point? a.
The connection is automatically dropped at 25 meters.
b.
The connection speed decreases. c.
The connection speed increases.
d.
The connection frequency changes from 2.4 GHz to 5 GHz.
5.
In order to accommodate additional wireless users over a wider area, which configuration should be used? a.
ad hoc b.
Basic Service Set c.
Extended Service Set d.
Channel Access Set
6.
When a packet reaches the MAC layer (or the Data Link layer in the OSI model) these segments are formally known as frames.
True or False?
7.
The IEEE 802.11 standard specifies six categories of MAC frame formats. True or False ?
8.
At regular intervals the AP in an infrastructure network or wireless device in an ad hoc network sends a data frame to both announce its presence and to provide the necessary information for other devices to join the network. True or False ?
9.
In passive scanning, the wireless device must first send out a management probe request frame on each available channel and then wait for an answer from all available APs. True or False ?
10.
Because wireless LANs cannot limit access to the RF signal by walls or doors, wireless authentication requires the wireless device to be authenticated prior to being connected to the network. True or False?
11.
_____ authentication requires the wireless device to correctly encrypt the challenge text . shared key

12.
Once a wireless device is authenticated the final step is to be accepted into the wireless network is a process known as _____. association
13.
The IEEE 802.11 standard specifies two procedures for transmitting on the
WLAN, distributed coordination function (DCF) and an optional _____. point coordination function (PCF)
14.
Instead of using Ethernet CSMA/CD, IEEE WLANs use _____. CSMA/CA
15.
Because IEEE 802.11 authentication is weak, another option is to use _____. digital certificates
16.
Explain why Carrier Sense Multiple Access/Collision Detection cannot be used on a WLAN.
CSMA/CD cannot be used for wireless networks for two reasons. First, collision detection is very difficult with wireless transmissions. With CSMA/CD, the stations must be able to transmit and listen at the same time. However, in radio systems the signal from a transmitting station is so strong that it will overpower that same station’s ability to simultaneously receive a transmission. In short, while it is transmitting, a station “drowns out” its own ability to detect a collision. A second factor that makes collision detection so difficult with wireless transmission is that all stations would have to be able to detect transmissions from all other stations at all times. In a wireless environment that covers a large area, a station may not be in range of all other stations. Laptops may all be within range of the access point but not within range of each other.
17.
Explain how virtual carrier sensing works.
A Request to Send (RTS) frame is transmitted by a wireless device to the access point. This frame contains a duration field that indicates the length of time needed for both the transmission and the returning ACK frame. The access point as well as all stations that can receive the RTS frame are alerted that the wireless device needs to reserve the medium for a specific period of time. Each receiving station stores that information in its net allocation vector (NAV). No station can transmit if the
NAV contains a value other than zero. The access point then responds back to the wireless device with a Clear to Send (CTS) frame that alerts all devices that medium is now being reserved and they should suspend any transmissions. Once the wireless device receives the CTS frame it can then proceed with transmitting its frame
18.
How does fragmentation reduce collisions?
Fragmentation involves dividing the data to be transmitted from one large frame into several smaller ones. Sending many smaller frames instead of one large frame reduces the amount of time that the wireless medium is being used and likewise reduces the probability of collisions.
19.
Why is Quality of Service (QoS) important to WLANs?

The DCF contention method was intended to be a “fair” approach to wireless transmissions. Although DCF works well for it data transmissions, the same is not true for real-time traffic that is time dependent. These types of transmissions, like voice or video, depend heavily upon each frame arriving very quickly one after the other, whereas data transmissions are not as sensitive to time. Delays in transmission can result in a video that “freezes” on the screen or a conversation that has gaps of dead space. DCF cannot distinguish between voice, video, and data frames to assure that time-sensitive frames have a priority. This capability is known as Quality of Service (QoS). QoS on WLANs has become an increasing area of interest with the widespread adoption of Voice over IP (VoIP) telephony. VoIP uses
IP-based data packet switching networks to transmit voice communications. VoIP over WLANs holds tremendous potential by providing workers who are not regularly at their desks more flexibility. It can also reduce operating costs associated with use of cell phones and private radio walkie-talkie systems
20.
Explain how power management functions on an infrastructure network.
In an infrastructure WLAN when a mobile 802.11 devices is running on its battery and goes into sleep mode, the access point is informed. The access point keeps a record of which stations are awake and which are sleeping. As the access point receives transmissions it first checks its records to determine if that station is in sleep mode. If it is sleeping, the access point temporarily stores those frames. At set times the access point will send out a beacon frame to all stations. This frame contains a list, known as the traffic indication map (TIM), of the stations that have buffered frames waiting at the access point. At that same set time all stations that have been sleeping will switch from sleep mode into an active listening mode. This is possible because a station’s local timer does not sleep. If a station learns that it has buffered frames waiting for it, that station can send a request to the access point to have those frames forwarded to it. If it has no buffered frames, it can return to sleep mode.