Loopcomm LP-9327H, Руководство пользователя

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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.
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.
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.