User's Manual

Configuration Parameters 21
RTS/CTS
The 802.11a standard supports optional RTS/CTS communication based on packet
size. By default, RTS/CTS communication is disabled.
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 may configure a Harmony 802.11a PCI Card to never use RTS/CTS (i.e., disable
RTS/CTS) or to use RTS/CTS for packets over a certain size.
For example, if the RTS/CTS Threshold is set to 1000 Bytes, then a sending radio will
use RTS/CTS before transmitting any packet 1000 Bytes or larger.
The RTS/CTS Threshold parameter supports a range between 1 and 2345 Bytes. When
set to 1, a sending radio will use RTS/CTS before transmitting any packet.
Wired Equivalent Privacy
The IEEE 802.11a standard specifies an optional encryption feature, known as Wired
Equivalent Privacy or WEP, that is designed to provide a wireless LAN with a security
level equal to what is found on a wired Ethernet network.
WEP encrypts the data portion of each packet exchanged on the 802.11a network
using a 40-bit, 128-bit, or 152-bit encryption algorithm to prevent unauthorized
devices from intercepting confidential data.
To use WEP Encryption, all 802.11a devices within the same Extended Service Set
(ESS) or Ad Hoc network must have WEP enabled and must have the same WEP Keys.
A device that has the wrong WEP Keys or does not have WEP enabled will not be able
to exchange data with the network.