PLANET WNL-U555HA - Manual (Page 51)

PLANET 802.11n Wireless High Power USB Adapte r
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corrupted, can be resent faster than a larger fragment. Fragmentation increases overhead, so you'll
want to keep this value as close to the maximum value as possible.
26. RTS(Request To Send) Threshold
The RTS threshold is the packet size at which packet transmission is governed by the RTS/CTS
transaction. The IEEE802.11-1997 standard allows for short packets to be transmitted without
RTS/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.