CNET WNUD1150H, User Manual

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CNet Technology Inc.
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21. Wi-Fi Protected Access (WPA)
The Wi-Fi Alliance put together WPA as a data encryption method for 802.11 wireless LANs. WPA is an indus-
try-supported, pre-standard version of 802.11i utilizing the Temporal Key Integrity Protocol (TKIP), which fixes
the problems of WEP, including using dynamic keys.
22. Wide Area Network (WAN)
A WAN consists of multiple LANs that are tied together via telephone services and / or fiber optic cabling.
WANs may span a city, a state, a country, or even the world
23. Wired Equivalent Privacy (WEP)
Now widely recognized as flawed, WEP was a data encryption method used to protect the transmission between
802.11 wireless clients and APs. However, it used the same key among all communicating devices. WEP’s
problems are well-known, including an insufficient key length and no automated method for distributing the
keys. WEP can be easily cracked in a couple of hours with off-the-shelf tools.
24. Wireless LAN (WLAN)
A wireless LAN does not use cable to transmit signals, but rather uses radio or infrared to transmit packets
through the air. Radio Frequency (RF) and infrared are the commonly used types of wireless transmission. Most
wireless LANs use spread spectrum technology. It offers limited bandwidth, usually under 11Mbps, and users
share the bandwidth with other devices in the spectrum; however, users can operate a spread spectrum device
without licensing from the Federal Communications Commission (FCC).
25. Fragment Threshold
The proposed protocol uses the frame fragmentation mechanism defined in IEEE 802.11 to achieve parallel
transmissions. A large data frame is fragmented into several fragments each of size equal to fragment threshold.
By tuning the fragment threshold value, we can get varying fragment sizes. The determination of an efficient
fragment threshold is an important issue in this scheme. If the fragment threshold is small, the overlap part of
the master and parallel transmissions is large.
This means the spatial reuse ratio of parallel transmissions is high. In contrast, with a large fragment threshold,
the overlap is small and the spatial reuse ratio is low. However high fragment threshold leads to low fragment
overhead. Hence there is a trade-off between spatial re-use and fragment overhead. Fragment threshold is the
maximum packet size used for fragmentation. Packets larger than the size programmed in this field will be
fragmented If you find that your corrupted packets or asymmetric packet reception (all send packets, for exam-
ple). You may want to try lowering your fragmentation threshold. This will cause packets to be broken into
smaller fragments. These small fragments, if corrupted, can be resent faster than a larger fragment. Fragmenta-
tion 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 sta-
tion 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 net-
work 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