3Com 3CRWX120695A, 3CRWX440095A Configuration Manual page 152

152 C 6: C MAP A P
HAPTER ONFIGURING CCESS OINTS
To guard against interference, an 802.11b/g radio in protection mode
sends messages while 802.11g traffic at higher data rates is being sent,
to inform 802.11b devices about the 802.11g traffic and reserve
bandwidth for the traffic. Protection mode remains in effect until 60
seconds after the last 802.11b traffic is detected by the 802.11b/g radio.
Protection mode lowers overall traffic throughput due to the additional
messages sent by 802.11b/g radios. You can configure the 802.11b/g
radios in a radio profile to reject association attempts by 802.11b clients
so that protection mode is less likely to be required. In this case, the
802.11b/g radios require a client to support all the 802.11g rates.
Even when association of 802.11b clients is disabled, if an 802.11b/g
radio detects a beacon from an 802.11b network, the radio enters
protection mode to protect against interference.
To configure 802.11b/g radios to reject association attempts from
802.11b clients, use the following command:
set radio-profile name 11g-only {enable | disable}
To configure the 802.11b/g radios in radio profile rp1 to allow
associations from 802.11g clients only, type the following command:
WX1200# set radio-profile rp1 11g-only enable
success: change accepted.
Changing the Preamble Length By default, 802.11b/g radios
advertise support for frames with short preambles and can support
frames with short or long preambles.
An 802.11b/g radio generates unicast frames to send to a client with the
preamble length specified by the client. An 802.11b/g radio always uses a
long preamble in beacons, probe responses, and other broadcast or
multicast traffic.
Generally, clients assume access points require long preambles and
request to use short preambles only if the access point with which they
are associated advertises support for short preambles. You can disable
the advertisement of support for short preambles by setting the preamble
length value to long. In this case, clients assume that the access point
supports long preambles only and the clients request long preambles.