Which of the following is a secure method of client device authentication onto a WLAN?
Answer(s): B
The IEEE 802.11 standard specifies two methods of authentication: Open System authenticationand Shared Key authentication. The simpler and also the more secure of the two methods is Open System authenticationOpen System AuthenticationOpen System authentication is a method of null authentication and is specified by the IEEE 802.11 as the default setting in wireless LAN equipment.Using this method of authentication, a station can associate with any access point that uses Open System authenticationbased only on having the right service set identifier (SSID). The SSIDs must match on both the access point and client before a client is allowed to complete the authentication process. Uses of the SSID relating to security will be discussed in Chapter 10 (Security).The Open System authentication process is used effectively in both secure and non-secure environments.Open System Authentication ProcessThe Open System authentication process occurs as follows:1. The wireless client makes a request to associate to the access point2. The access point authenticates the client and sends a positive response and the client becomes associated (connected)
A change in the direction and intensity of a group of waves after passing by an obstacle or the bending waves around an object is referred to as?
Answer(s): A
Diffraction occurs when the radio path between the transmitter and receiver is obstructed by a surface that has sharp irregularities or an otherwise rough surface. At high frequencies, diffraction, like reflection, depends on the geometry of the obstructing object and the amplitude, phase, and polarization of the incident wave at the point of diffraction. Diffraction is commonly confused with and improperly used interchangeably with refraction.
Attenuation is the term used to describe?
Attenuation is simply a reduction of signal strength during transmission. You represent attenuation in decibels (dB), which is ten times thelogarithm of the signal power at a particular input divided by the signal power at an output of a specified medium. For example, an office wall (i.e., medium) that changes the propagation of an RF signal from a power level of 200 milliwatts (the input) to 100 milliwatts (the output) represents 3 dB of attenuation. Consequently, positive attenuation causes signals to become weaker when traveling through the medium.When signal power decreases to relatively low values, the receiving 802.11 radio will likely encounter bit errors when decoding the signal. This problem worsens when significant RF interference is presentExcessive attenuation causes the network's throughput to decrease because of operation at a lower data rate and the additional overhead necessary to retransmit the frames. Generally, this means that the user is operating within the outer bounds of an access point's range. There's enough attenuation present to decrease signal power below acceptable values. At worst case, signal power loss due to attenuation becomes so low that affected users will lose connectivity to the network
Which spread spectrum technologies exhibit resistance to narrowband RF interference by design?
Frequency hopping spread spectrum is a spread spectrum technique that uses frequency agility to spread the data over more than 83 MHz. Frequency agility refers to the radio's ability to change transmission frequency abruptly within the usable RF frequency band. In the case of frequency hopping wireless LANs, the usable portion of the 2.4 GHz ISM band is 83.5 MHz, per FCC regulation and the IEEE 802.11 standard. Both FHSS and DSSS technologies have their advantages and disadvantages, and it is incumbenton the wireless LAN administrator to give each its due weight when deciding howto implement a wireless LAN. This section will cover some of the factors that shouldbe discussed when determining which technology is appropriate for your organization, including:? Narrowband interference? Co-location? Cost? Equipment compatibility & availabilityThe advantages of FHSS include a greater resistance to narrow band interference. DSSS systemsmay be affected by narrow band interference more than FHSS because of the use of22 MHz wide contiguous bands instead of the 79 MHz used by FHSS. This fact may be a serious consideration if the proposed wireless LAN site is in an environment that has such interference present.
A 2.4 GHz Spread Spectrum phone located near an 802.11b compliant Access Point will not cause interference.
Answer(s): C
communications tower or other legitimate system, the wireless LAN administrator might have to consider using a wireless LAN system that utilizes a different set of frequencies. For example, if an administrator were responsible for the design and installation of an RF network at a large apartment complex, special considerations might be in order. If an RF interference source were a large number of 2.4 GHz spread spectrum phones, baby monitors, and microwave ovens in this apartment complex, then the administrator might choose to implement 802.11a equipment that uses the 5 GHz UNII bands instead of 802.11b equipment that shares the 2.4 GHz ISM band with these other devices. Unintentional jamming occurs regularly due to many different devices across many different industries sharing the 2.4 GHz ISM band with wireless LANs. Malicious jamming is not a common threat. The reason RF jamming is not very popular among hackers is that it is fairly expensive to mount an attack, considering the cost of the required equipment,
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