Wireless Technologies Questions and Answers

Answer: B

Statement i is false and statement ii is true. An SSID is a human-readable text string, but its maximum length is 32 bytes, not 2000 bytes. The SSID acts as a single shared identifier between the access points and the clients of a wireless network. So the second option, i-False and ii-True, is correct, and the options that call i true are wrong. The 32-byte limit is the same figure that is given for the SSID in the standard for wireless networks.

Answer: B

The true statements are I and III only.

I is true: in the 2.4 GHz band, channels 1, 6 and 11 do not overlap, so at least three non-overlapping channels are available (and many more at 5 GHz).

III is true: 802.11 uses a stop-and-wait acknowledgement at the MAC layer, so every unicast data frame received correctly is ACKed; broadcast frames are not.

II is false: a wireless station cannot reliably detect collisions while transmitting, so 802.11 uses CSMA/CA, collision avoidance. The RTS-CTS exchange reserves the medium to avoid collisions, notably from hidden terminals; it does not detect them. That rules out every option containing II.

Answer: A

Correct answer: 3

802.11g shares the 2.4 GHz band with 802.11b and so shares its channel plan: eleven overlapping channels of which only 1, 6 and 11 can be used together. The higher data rate changes nothing about the spectrum available, which is why 802.11a’s twelve channels remain its principal advantage.

Answer: B

The Cisco Unified Wireless Solution is a great product, but you must purchase specialized devices. Cisco managed access points and a controller are the devices you need to purchase to run the Unified Wireless Solution.

Answer: D

Correct answer: 54Mbps

802.11a reaches 54 Mbps, the same headline rate as 802.11g. The two differ in band rather than in speed - 5 GHz against 2.4 - which is why 802.11a offers more non-overlapping channels and less interference but a shorter range.

Answer: A

Correct answer: About 65-75 feet

802.11a reaches only about 65 to 75 feet at its full 54 Mbps. It is the shortest range of the three standards here, because 5 GHz signals attenuate more rapidly in air and are absorbed more readily by walls and furnishings than 2.4 GHz. That is the price paid for the extra channels and the quieter band.

Answer: B

Correct answer: 12

802.11a has twelve non-overlapping channels in the 5 GHz U-NII bands, four times what 2.4 GHz offers. The channels there are spaced so they do not overlap at all, which makes the channel plan for a dense deployment far easier and is the main practical reason for choosing 5 GHz.

Answer: D

Correct answer: 5GHz

802.11a operates in the 5 GHz U-NII bands. Note that two of the options are given in Gbps - a data rate, not a frequency - so they can be eliminated on units alone before any knowledge of the standard is applied. The move to 5 GHz is what gives 802.11a its twelve non-overlapping channels and its shorter range, since higher frequencies attenuate faster.

Answer: B

Correct answer: 11Mbps

802.11b reaches 11 Mbps, with fallback rates of 5.5, 2 and 1 Mbps as the signal weakens. It is the slowest of the three standards here and the longest ranging, which is the same trade-off seen throughout this topic - a more robust modulation carries less data but survives a weaker signal.

Answer: B

Correct answer: AWPP

The Adaptive Wireless Path Protocol is Cisco’s proprietary mesh routing protocol. Each mesh access point uses it to discover its neighbours and choose the best path back to the rooted access point, taking signal quality and the number of hops into account, and to reroute automatically when a link degrades. LWAPP is the protocol between a lightweight access point and its controller, and STP is a wired Layer 2 protocol.