User's Manual

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for networks with many clients. With many clients, and a high network load, there will be many more collisions. By
lowering the RTS threshold, there may be fewer collisions, and performance should improve. Basically, with a faster RTS
threshold, the system can recover from problems faster. RTS packets consume valuable bandwidth, however, so setting this
value too low will limit performance.
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ٛ 27. Beacon Interval
ٛ In addition to data frames that carry information from higher layers, 802.11 includes management and control frames that
support data transfer. The beacon frame, which is a type of management frame, provides the "heartbeat" of a wireless LAN,
enabling stations to establish and maintain communications in an orderly fashion. Beacon Interval represents the amount of
time between beacon transmissions. Before a station enters power save mode, the station needs the beacon interval to know
when to wake up to receive the beacon (and learn whether there are buffered frames at the access point).
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ٛ 28. Preamble Type
ٛ There are two preamble types defined in IEEE 802.11 specification. A long preamble basically gives the decoder more time
to process the preamble. All 802.11 devices support a long preamble. The short preamble is designed to improve efficiency
(for example, for VoIP systems). The difference between the two is in the Synchronization field. The long preamble is 128
bits, and the short is 56 bits.
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29. WPA2
It is the second generation of WPA. WPA2 is based on the final IEEE 802.11i amendment to the 802.11 standard.
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ٛ 30. Temporal Key Integrity Protocol (TKIP)
The Temporal Key Integrity Protocol, pronounced tee-kip, is part of the IEEE 802.11i encryption standard for wireless
LANs. TKIP is the next generation of WEP, the Wired Equivalency Protocol, which is used to secure 802.11 wireless LANs.
TKIP provides per-packet key mixing, a message integrity check and a re-keying mechanism, thus fixing the flaws of WEP.
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ٛ 31. 802.1x Authentication
802.1x is a framework for authenticated MAC-level access control, defines Extensible Authentication Protocol (EAP) over
LANs (WAPOL). The standard encapsulates and leverages much of EAP, which was defined for dial-up authentication with
Point-to-Point Protocol in RFC 2284. Beyond encapsulating EAP packets, the 802.1x standard also defines EAPOL
messages that convey the shared key information critical for wireless security.
32. Advanced Encryption Standard (AES)
Security issues are a major concern for wireless LANs, AES is the U.S. government’s next-generation
cryptography algorithm, which will replace DES and 3DES.