Proxim Harmony 802.11b User Manual page 19

RTS/CTS Threshold
The 802.11b specification supports optional RTS/CTS communication based on
packet size.
Without RTS/CTS, a sending radio listens to see if another radio is already using the
medium before transmitting a data packet. If the medium is free, the sending radio
transmits its packets. However, there is no guarantee that another radio is not transmit-
ting a packet at the same time, causing a collision.
When RTS/CTS occurs, the sending radio first transmits a Request to Send (RTS)
packet to confirm that the medium is clear. When the receiving radio successfully
receives the RTS packet, it transmits back a Clear to Send (CTS) packet to the sending
radio. When the sending radio receives the CTS packet, it sends the data packet to the
receiving radio. The RTS and CTS packets contain a reservation time to notify other
radios that the medium is in use for a specified period of time. This helps to minimize
collisions.
While RTS/CTS adds overhead to the radio network, RTS/CTS is particularly useful
for large packets which take time to resend if a collision occurs during an attempt to
send.
You may configure a Harmony 802.11b Access Point to always use RTS/CTS, never
use RTS/CTS, or use RTS/CTS for packets over a certain size.
For example, if the RTS/CTS Threshold is set to 1000 Bytes, than a sending radio will
use RTS/CTS before transmitting any packet 1000 Bytes or larger.
The RTS/CTS Threshold parameter supports a range between 0 and 1513 Bytes (which
is the largest Ethernet packet).
If set to 0, then a sending radio will use RTS/CTS before sending any packet. If set to
1513, then a sending radio will not use RTS/CTS for any packets except those that are
1513 Bytes.
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