User's Manual

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.

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).

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.

29. WPA2

It is the second generation of WPA. WPA2 is based on the final IEEE 802.11i amendment to the 802.11 standard.

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.

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 m

ssages

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.