Brocade Mobility Access Point System Reference Guide (Supporting software release 5.5.0.0 and later) - Manual (Page 109)

Brocade Mobility Access Point System Reference Guide 99
53-1003100-01
5
10. Set the following profile WLAN Properties for the selected access point radio:
Use the Feed WLAN Packets to Sensor drop-down menu to radio’s tap mode of operation. Options
include, Off, Inline and Promiscuous. The default setting is Off.
11. Select the WLAN Mapping/Mesh Mapping tab.
Beacon Interval Set the interval between radio beacons in milliseconds (either 50, 100 or 200). A beacon is a
packet broadcast by adopted radios to keep the network synchronized. Included in a beacon is
information such as the WLAN service area, the radio 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 value is 100 milliseconds.
DTIM Interval BSSID Set a DTIM Interval to specify a period for Delivery Traffic Indication Messages (DTIM). A DTIM is
periodically included in a beacon frame transmitted from adopted radios. 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 point) 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.
RTS Threshold Specify a Request To Send (RTS) threshold (from 1 - 2,347 bytes) for use by the WLAN's adopted
access point radios. RTS is a transmitting station's signal that requests a Clear To Send (CTS)
response from a receiving client. This RTS/CTS procedure clears the air where 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 point
radios. 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.
Short Preamble If using an 802.11bg radio, select this option for the radio to transmit using a short preamble.
Short preambles improve throughput. However, some devices (SpectraLink phones) require long
preambles. The default value is disabled.
Guard Interval Use the drop-down menu to specify a Long or Any guard interval. The guard interval is the space
between symbols (characters) being transmitted. The guard interval is there to eliminate
inter-symbol interference (ISI). ISI occurs when echoes or reflections from one symbol interfere with
another symbol. Adding time between transmissions allows echo's and reflections to settle before
the next symbol is transmitted. A shorter guard interval reduces overhead and increases data rates
by up to 10%.The default value is Long.
Probe Response Rate Use the drop-down menu to specify the data transmission rate used for the transmission of probe
responses. Options include, highest-basic, lowest-basic and follow-probe-request (default setting).
Probe Response Retry Select this option to retry probe responses if they are not acknowledged by the target wireless
client. The default value is enabled.