Extreme Networks Altitude 4700 Series Product Reference Manual page 180

Network Management
4 Configure the Performance field to set the preamble, thresholds values and QoS values for the radio.
Support Short
Preamble Interval
RTS Threshold
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The preamble is approximately 8 bytes of packet header
generated by the Access Point and attached to a packet
prior to transmission from the 802.11b radio. The preamble
length for 802.11b transmissions is rate dependant. A
short preamble is 50% shorter than a long preamble.
Leave the checkbox unselected if in a mixed MU/AP
environment, as MUs and the Access Point are required to
have the same RF Preamble settings for interoperability.
The default is Disabled. The preamble length for 802.11a
and 802.11g transmissions is the same, with no long or
short preamble lengths.
RTS allows the access point to use RTS (Request To
Send) on frames longer than the specified length. The
default is 2341bytes.
Altitude 4700 Series Access Point Product Reference Guide