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Configuration
23
Fragmentation
The Skyline 802.11a Access Point supports an optional feature called Fragmentation.
In harsh radio environments, 802.11a devices may have difficulty transmitting large
packets that exceed a certain size. However, when Fragmentation is enabled, the
802.11a Access Point can break up large packets into a number of smaller packets
(called "fragments") that can be successfully transmitted to another 802.11a device.
The receiving 802.11a device then reassembles the original packet once it has
received all of the fragments.
You can configure the Access Point to never use Fragmentation or to fragment only
those packets that exceed a certain size. For example, if the Fragmentation Threshold
is set to 1000 Bytes, then a sending radio will fragment any packet 1000 Bytes or
larger before transmitting.
The Fragmentation Threshold supports a range between 256 and 2346 Bytes. If set to
256, then a sending radio will fragment all packets 256 Bytes or larger. If set to 2346,
then a sending radio will fragment only those radio packets that are 2346 Bytes or
larger. By default, Fragmentation is disabled.
RTS/CTS
The 802.11a standard 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
transmitting 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. This helps to minimize
collisions.
While RTS/CTS adds overhead to the radio network, it is particularly useful for large
packets that take longer to resend after a collision occurs.
You can configure a Skyline 802.11a Access Point to always use RTS/CTS, never use
RTS/CTS, or use RTS/CTS for packets over a certain size (RTS/CTS Threshold). The RTS/
CTS Threshold supports a range between 256 and 2346 Bytes. If set to 256, then a
sending radio will use RTS/CTS before sending any packet that is 256 Bytes or larger. If
set to 2346, then a sending radio will not use RTS/CTS for any packets except those
that are 2346 Bytes or larger. By default, RTS/CTS ia set to always off.
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