qpcom QP-W4400NUSB, Руководство пользователя

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Glossary
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CTS transactions. Each station can have a different RTS threshold. RTS/CTS is used when the data
packet size exceeds the defined RTS threshold. With the CSMA/CA transmission mechanism, the
transmitting station sends out an RTS packet to the receiving station, and waits for the receiving
station to send back a CTS (Clear to Send) packet before sending the actual packet data. This
setting is useful 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 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.