Brocade Communications Systems RFS6000 System Reference Manual page 192

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Short Preambles only If using an 802.11bg radio, select this checkbox for the radio to transmit using a short preamble. Short preambles
improve throughput. However, some devices (SpectraLink phones) require long preambles. This checkbox does not
display if using an 802.11a radio.
RTS Threshold Specify a Request To Send (RTS) threshold (in bytes) for use by the WLAN's adopted Access Ports.
RTS is a transmitting station's signal that requests a Clear To Send (CTS) response from a receiving station. This
RTS/CTS procedure clears the air where many Clients are contending for transmission time. Benefits include fewer
data collisions and better communication with nodes that are hard to find (or hidden) because of other active nodes
in the transmission path.
Control RTS/CTS by setting an RTS threshold. This setting initiates an RTS/CTS exchange for data frames larger than
the threshold, and sends (without RTS/CTS) any data frames smaller than the threshold.
Consider the trade-offs when setting an appropriate RTS threshold for the WLAN's Access Ports. A lower RTS
threshold causes more frequent RTS/CTS exchanges. This consumes more bandwidth because of additional latency
(RTS/CTS exchanges) before transmissions can commence. A disadvantage is the reduction in data-frame
throughput. An advantage is quicker system recovery from electromagnetic interference and data collisions.
Environments with more wireless traffic and contention for transmission make the best use of a lower RTS
threshold.
A higher RTS threshold minimizes RTS/CTS exchanges, consuming less bandwidth for data transmissions. A
disadvantage is less help to nodes that encounter interference and collisions. An advantage is faster data-frame
throughput. Environments with less wireless traffic and contention for transmission make the best use of a higher
RTS threshold. Default is 2346.
In 802.11b/g mixed RTS/CTS happens automatically. There is no way to disable RTS/CTS unless the network and all
the devices used are 802.11g or 802.11a only. The proper co-existence of 802.11b and 802.11g is ensured through
RTS/CTS mechanism. On 802.11g radios, CTS-to-self is enabled irrespective of whether or not 11b rates are
enabled or disabled.
When ERP Protection is ON, the 11bg radio will perform a CTS-to-self before it transmits the frame.
Beacon Interval Specify a beacon interval in units of 1,024 microseconds (K-us). This is a multiple of the DTIM value, for example,
100: 10. (See "DTIM Period" below). A beacon is a packet broadcast by the adopted Access Ports to keep the
network synchronized. Included in a beacon is information such as the WLAN service area, the radio-port address,
the broadcast destination addresses, a time stamp, and indicators about traffic and delivery such as a DTIM.
Increase the DTIM/beacon settings (lengthening the time) to let nodes sleep longer and preserve battery life.
Decrease these settings (shortening the time) to support streaming-multicast audio and video applications that are
jitter-sensitive. The default is
100 K-us.
Self Healing Offset When an Access Port increases its power to compensate for a failure, power is increased to the country's regulatory
maximum. Set the Self Healing Offset to reduce the country's regulatory maximum power if Access Ports are
situated close to each other or if an Access Port uses an external antenna.
DTIM Periods Select the
This is a divisor of the beacon interval (in milliseconds), for example, 10:100. (See "Beacon Interval"above). A DTIM
is periodically included in the beacon frame transmitted from adopted Access Ports. The DTIM period determines
how often the beacon contains a DTIM, for example, 1 DTIM for every 10 beacons. The DTIM indicates broadcast
and multicast frames (buffered at the Access Port) are soon to arrive. These are simple data frames that require no
acknowledgement, so nodes sometimes miss them. Increase the DTIM/beacon settings (lengthening the time) to let
nodes sleep longer and preserve their battery life. Decrease these settings (shortening the time) to support
streaming-multicast audio and video applications that are jitter-sensitive. The default DTIM period is 10 beacons for
BSS 1-4.
Aggregation This allows the type 'n' packets to be aggregated before transmission. This feature is available only for type 'n'
radios.
180
DTIM periods
button to specify a period for Delivery Traffic Indication Messages (DTIM) for BSS IDs 1-4.
Brocade Mobility RFS4000, RFS6000, and RFS7000 System Reference Guide
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