User's Manual

FREQUENTLY ASKED QUESTIONS (FAQ)
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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.
5.12 What is 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).
5.13 What is 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.
5.14 What is SSID Broadcast?
Broadcast of SSID is done in access points by the beacon. This announces your access point
(including various bits of information about it) to the wireless world around it. By disabling that
feature, the SSID configured in the client must match the SSID of the access point.
Some wireless devices don't work properly if SSID isn't broadcast (for example the D-link DWL-120
USB 802.11b adapter). Generally if your client hardware supports operation with SSID disabled, it's
not a bad idea to run that way to enhance network security. However it's no replacement for WEP,
MAC filtering or other protections.
5.15 What is Wi-Fi Protected Access (WPA)?
Wi-Fi’s original security mechanism, Wired Equivalent Privacy (WEP), has been viewed as
insufficient for securing confidential business communications. A longer-term solution, the IEEE
802.11i standard, is under development. However, since the IEEE 802.11i standard is not expected
to be published until the end of 2003, several members of the WI-Fi Alliance teamed up with
members of the IEEE 802.11i task group to develop a significant near-term enhancement to Wi-Fi
security. Together, this team developed Wi-Fi Protected Access.
To upgrade a WLAN network to support WPA, Access Points will require a WPA software upgrade.
Clients will require a software upgrade for the network interface card, and possibly a software update
for the operating system. For enterprise networks, an authentication server, typically one that
supports RADIUS and the selected EAP authentication protocol, will be added to the network.
5.16 What is WPA2?
It is the second generation of WPA. WPA2 is based on the final IEEE 802.11i amendment to the
802.11 standard.