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Xentino XAIR A400N User Manual
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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 bit
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.
5.17 What is 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.