CWNA Assessment Test Questions and Answers scored A+

CWNA Assessment Test Questions and Answers scored A +At which layers of the OSI model does 802.11 technology operate? • Data-link & Physical layers EXPLANATION: The IEEE 802.11-2012 standard defines communication mechanisms at only the Physical layer and MAC sublayer of the Data-Link layer of the OSI model. Which Wi-Fi Alliance certification defines the mechanism for conserving battery life that is critical for handheld devices such as bar code scanners and VoWiFi phones? • WMM-PS EXPLANATION: WMM-PS helps conserve battery power for devices using Wi-Fi radios by managing the time the client device spends in sleep mode. Conserving battery life is critical for handheld devices such as bar code scanners and VoWiFi phones. To take advantage of power-saving capabilities, both the device and the access point must support WMM Power Save. Which of these frequencies has the longest wavelength? • 750 KHz EXPLANATION: A 750 KHz signal has an approximate wavelength of 1,312 feet, or 400 meters. A 252 GHz signal has an approximate wavelength of less than 0.05 inches, or 1.2 millimeters. Remember, the higher the frequency of a signal, the smaller the wavelength property of an electromagnetic signaL. Which of these terms can best be used to compare the relationship between two radio waves that share the same frequency? • Phase EXPLANATION: Phase involves the positioning of the amplitude crests and troughs of two wave- forms. A bridge transmits at 10 mW. The cable to the antenna produces a loss of 3 dB, and the antenna produces a gain of 20 dBi. What is the EIRP? • 500 mW EXPLANATION: The 10 mW of power is decreased by 3 dB, or divided by 2, giving 5 mW. This is then increased by 20 dBi, or multiplied by 10 twice, giving 500 mW. dBi is an expression of what type of measurement? • Antenna gain EXPLANATION: Theoretically, an isotropic radiator can radiate an equal signal in all directions. An antenna cannot do this because of construction limitations. However, antennas are often referred to as isotropic radiators because they radiate RF energy. The gain, or increase, of power from an antenna when compared to what an isotropic radiator would generate is known as decibels isotropic (dBi). Another way of phrasing this is decibel gain referenced to an isotropic radiator, or change in power relative to an antenna. dBi is a measurement of antenna gain. What are some possible effects of voltage standing wave ratio (VSWR)? • Decreased signal strength • Transmitter failure • Erratic amplitude. EXPLANATION: Reflected voltage caused by an impedance mismatch may cause a degradation of amplitude, erratic signal strength, or even the worst-case scenario of transmitter burnout. When installing a higher-gain omnidirectional antenna, which of the following occurs? • The horizontal coverage increases • The vertical coverage decreases. EXPLANATION: When the gain of an omnidirectional antenna is increased, the vertical cover- age area decreases while the horizontal coverage area is increased. 802.11a OFDM radios are backward compatible with which IEEE 802.11 radios? • OFDM is not backward compatible because of its 5 GHz band. EXPLANATION: 802.11a (OFDM) radios transmit in the 5 GHz U-NII bands and are not compatible with 802.11 legacy (FHSS) radios, 802.11 legacy (DSSS) radios, 802.11b (HR-DSSS) radios, or 802.11g (ERP) radios, which transmit in the 2.4 GHz ISM frequency band. 802.11a (OFDM) radios are forward compatible but not backward compatible with 802.11n (HT) radios. 802.11n radios, which can transmit on either frequency band, are backward compatible with 802.11a radios as well as 802.11g (ERP), 802.11b (HR- DSSS), and 802.11 legacy (DSSS) radios. None of these radio technologies are backward compatible with 802.11 legacy (FHSS) radios. Which IEEE 802.11 amendment specifies the use of up to eight spatial streams of modulated data bits? • IEEE 802.11ac EXPLANATION: The 802.11ac-2013 amendment defines the use of 256-QAM modulation, up to eight spatial streams, multiuser MIMO, 80 MHz channels, and 160 MHz channels. 802.11 MIMO technology and 40 MHz channels debuted with the ratification of the 802.11n-2009 amendmenT. The FCC is preparing for the advent of 802.11ac technology that can use 80 MHz and 160 MHz channels, and therefore, more unlicensed spectrum is needed. What are the newly proposed 5 GHz frequency bands? • U-NII-2B • U-NII-4 EXPLANATION: In January 2013, the FCC announced that 195 MHz of additional spectrum space would be made available for unlicensed use. A new 120 MHz wide band called U-NII-2B, which occupies the frequency space of 5.35 GHz-5.47 GHz, and another new 75 MHz wide band called U-NII-4 occupies the 5.85 GHz-5.925 GHz frequency space. What signal characteristics are common in spread spectrum signaling methods? • Low power • Wide bandwidth EXPLANATION: A spread spectrum signal utilizes bandwidth that is wider than what is required to carry the data and has low transmission power requirements. A service set identifier is often synonymous with which of the following? • ESSID EXPLANATION: The logical network name of a wireless LAN is often called an ESSID (extended service set identifier) and is essentially synonymous with SSID (service set identifier), which is another term for a logical network name in the most common deployments of a WLAN. Which ESS design scenario is defined by the IEEE 802.11-2012 standard? • None of the above EXPLANATION: The IEEE 802.11-2012 standard defines an extended service set (ESS) as "a set of one or more interconnected basic service sets." However, the IEEE 802.11-2012 standard does not mandate any of the examples given in the options. What CSMA/CA conditions must be met before an 802.11 radio can transmit? • The NAV timer must be equal to zero. • The random backoff timer must have expired. • The CCA must be idle. • The proper interframe space must have occurred. EXPLANATION: Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) is a medium access method that utilizes multiple checks and balances to try to minimize collisions. These checks and balances can also be thought of as several lines of defense. The various lines of defense are put in place to hopefully ensure that only one radio is transmitting while all other radios are listening. The four lines of defense include the network allocation vector, the random backoff timer, the clear channel assessment, and interframe spacing. Beacon management frames contain which of the following information? • Channel information. • Destination IP address. • Basic data rate. • Traffic indication map (TIM). • Vendor proprietary information. • Time stamp & Spread spectrum parameter sets. EXPLANATION: The only information not contained in the beacon management frame is the destination IP address. The body of all 802.11 management frames contain only layer 2 information; therefore, IP information is not included in the frame. Other information that is included in a beacon includes security and QoS parameters. Metka Dragos was hired to perform a wireless packet analysis of your network. While performing the analysis, she noticed that many of the data frames were preceded by an RTS frame followed by a CTS frame. What could cause this phenomenon to occur? • An AP was manually configured with a low RTS/CTS threshold. • The network is a mixed-mode environment. EXPLANATION: AP radios can be manually configured to use RTS/CTS for all transmissions. This is usually done to diagnose hidden node problems. This network could also be a mixed-mode 802.11b (HR-DSSS) and 802.11g (ERP) network. The 802.11g nodes have enabled RTS/CTS as their protection mechanism. What is another name for an 802.11 data frame that is also known as a PSDU? • MPDU EXPLANATION: The technical name for an 802.11 data frame is MAC Protocol Data Unit (MPDU). An MPDU contains a layer 2 header, a frame body, and a trailer that is a 32-bit CRC known as the frame check sequence (FCS). Inside the frame body of an MPDU is a MAC Service Data Unit (MSDU), which contains data from the LLC and layers 3-7. Which WLAN device uses dynamic layer 2 routing protocols? • WLAN mesh access point EXPLANATION: WLAN mesh access points create a self-forming WLAN mesh network that automatically connects access points at installation and dynamically updates routes as more clients are added. Most WLAN mesh networks use dynamic layer 2 routing protocols with metrics such as RSSI, SNR, and client load. What term best describes the bulk of the data generated on the Internet being created by sensors, monitors, and machines? • Internet of Things (IoT) EXPLANATION: Over the years, most of the data generated on the Internet has been created by human beings. The theory of Internet of Things (IoT) is that in the future, the bulk of the data generated on the Internet might be created by sensors, monitors, and machines. 802.11 radio NICs used as client devices have begun to show up in many types of machines and devices. Wi-Fi technology is used in many different vertical markets. Which of these vertical markets use Wi-Fi for inventory control? • Retail • Manufacturing EXPLANATION: Warehouse, manufacturing, and retail environments often deploy wireless handheld devices, such as bar code scanners, which are used for inventory control. What term best describes how Wi-Fi can be used to identify customer behavior and shopping trends? • Retail analytics EXPLANATION: To further support and understand customers and their behaviors, retail analytic products are being installed to monitor customer movement and behavior. Strategi- cally placed access points or sensor devices listen for probe frames from Wi-Fi-enabled smartphones. MAC addresses are used to identify each unique device, and signal strength is used to monitor and track the location of the shopper. Retail analytics can identify the path the shopper took while walking through the store, along with the time spent in different areas of the store. This information can be used to identify shopping patterns and to analyze the effectiveness of in-store displays and advertise- ments. The hidden node problem occurs when one client station's transmissions are not heard by some of the other client stations in the coverage area of a basic service set (BSS). What are some of the consequences of the hidden node problem? • Retransmissions • Intersymbol interference (ISI) • Collisions • Decreased throughput EXPLANATION: The stations that cannot hear the hidden node will transmit at the same time that the hidden node is transmitting. This will result in continuous transmission collisions in a half-duplex medium. Collisions will corrupt the frames and they will need to be retransmitted. Any time retransmissions are necessary, more overhead is added to the medium, resulting in decreased throughput. Intersymbol interference is a result of multipath and not the hidden node problem. What are some potential causes of layer 2 retransmissions? • RF interference • Low signal-to-noise ratio (SNR) EXPLANATION: Layer 2 retransmissions can be caused by many different variables in a WLAN environment. Multipath, RF interference, hidden nodes, adjacent cell interference, and low signal-to-noise ratio (SNR) are all possible causes of layer 2 retransmissions. Which of these solutions would be considered strong WLAN security? • CCMP/AES EXPLANATION: Although you can hide your SSID to cloak the identity of your wireless network from script kiddies and nonhackers, it should be clearly understood that SSID cloaking is by no means an end-all wireless security solution. Because of spoofing and because of all the administrative work that is involved, MAC filtering is not considered a reliable means of security for wireless enterprise networks. WEP and Shared Key authentication are legacy 802.11 security solutions. CCMP/AES is defined as the default encryption type by the IEEE 802.11i security amendment. Cracking the AES cipher would take the lifetime of the sun using the tools that are available today. Which security standard defines port-based access control? • IEEE 802.1X EXPLANATION: The IEEE 802.1X standard is not specifically a wireless standard and often is mistakenly referred to as IEEE 802.11x. The IEEE 802.1X standard is a port-based access control standard. IEEE 802.1X provides an authorization framework that allows or disallows traffic to pass through a port and thereby access network resources.