www.lanpro.com
Wireless - Equipment - 2.4 GHz - LP-1521 User Manual High Speed Long Range Wireless Broad Band Router, with PoE
38
What is RTS (Request To Send) Threshold?
The RTS threshold is the packet size at which packet transmission is governed by the RTS/CTS transaction. The IEEE
802.11-1997 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.
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).
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.
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.
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.
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.
