Planet Networking & Communication WNAP-7206, Руководство пользователя

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User Manual of WNAP-7206
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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. Fragmentation increases
overhead, so you'll want to keep this value as close to the maximum value as possible.
A.11 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.
A.12 What is Beacon Interval?
In addition to data frames that carry information from higher layers, 802.11 include 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).
A.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.
A.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