WiFoo..The.Secrets.of.Wireless.Hacking [Electronic resources] نسخه متنی

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S/N ratio

signal-to-noise ratio. Signal-to-noise ratio, often written S/N or SNR, is a measure of signal strength relative to background noise. The ratio is measured in decibels (dB). A higher S/N ratio indicates better channel performance.

compression.

scalability

The ability to increase the availability capacity of any system, including wireless, security, and so on.

sector antenna

Typically an antenna similar to a patch antenna. Most sector antennas are designed with a horizontal beamwidth between 60 and 120 degrees. Many times sector antennas are used in groups of three or four to provide a complete 360-degree antenna.

Shared Key Authentication

An authentication algorithm defined in 802.11 in which the client is asked to respond back to the AP with a valid WEP key. It is considered less secure than open authentication, because the initial authentication challenge is clear, which could permit both the challenge and the response to be captured and compared, yielding the key.

single band

Referred to when a WLAN device has a single radio capable of operating on only one radio band (set of channels). The Cisco 1100 Series AP is a single-band unit.

sinusoidal signals

An electrical signal that varies with time proportionally to the sine of an angle. An example is alternating current (AC).

SNMP

Simple Network Management Protocol. A standard protocol for collecting statistics from networked devices.

spectral efficiency

The measurement of how much information is placed on a transmitted signal compared to the RF bandwidth required to transmit that signal.

spectrum

A series of radiated energies arranged in order of wavelength. The radio spectrum extends from 20 kHz upward.

spectrum analyzer

An instrument that can be used to view signals across a wide range of frequencies.

splitter/combiner

A transmission component that divides or sums power between two or more ports.

spread spectrum (SS)

A wideband modulation that imparts noiselike characteristics to an RF signal. This communications technique spreads a signal over a wide range of frequencies for transmission and then de-spreads it to the original data bandwidth at the receiver.

spurious emissions

Unwanted RF signals, emitted from a transmitter, that sometimes cause interference.

SSID

service set identifier. In the 802.11 standard, an identifier string of up to 32 characters that is used to uniquely identify a WLAN. Sometimes referred to as network name.

STP

Spanning Tree Protocol. A protocol defined by the IEEE 802.1d standard to prevent packets from looping indefinitely in a network that contains loops in the transmission paths.

stream cipher

An encryption architecture that generates a key stream from small "seed" values. This key stream is combined with the plaintext (data) to generate the "ciphertext" or encrypted data. The key stream may vary with same "seed," but streams will match at encryptor and decryptor, because they use the same algorithm.

switch

A multiport Ethernet bridge that typically has hardware acceleration to increase the performance of switching Ethernet frames between collision domains.