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Command Reference Guide
5.5
11
Default Values
By default, protection-mode is set to auto, type is set to cts-only, and the rate is set to 11.
Command History
Release 15.1
Functional Notes
Protection mode is used when 802.11b and 802.11g radios exist together on the same wireless local area
network (WLAN) network. 802.11g devices are required to be backwards-compatible with legacy 802.11b
devices. Both radios operate in the 2.4 GHz frequency range; however, each uses a different transmission
type. 802.11b radios use direct sequence spread spectrum (DSSS) for transmitting data, and 802.11g
radios use orthogonal frequency division multiplexing (OFDM) for transmitting data. Contention for media
access on 802.11 networks is managed via carrier sense multiple access with collision avoidance
(CSMA/CA), but the use of two different transmission types prevents 802.11b devices from hearing
transmission attempts on the shared radio frequency (RF) medium. Protection mode addresses this
problem and allows for coexistence of 802.11b and 802.11g devices on a network.
There are two protection mode types: CTS-only, also known as CTS-to-self, and RTS-CTS. Both types are
used when an 802.11g AP associates with an 802.11b client. Compared to a network that contains solely
802.11g clients, use of a protection mode reduces throughput. Compared to each other, CTS-only mode
requires slightly less protocol overhead than RTS-CTS mode. Protection frames must be transmitted at
802.11b rates (1 Mbps, 2 Mbps, 5.5 Mbps, or 11 Mbps) to ensure these frames are received and
processed by all clients on the network.
During CTS-only mode, clients that have a frame for transmission on the RF medium will first transmit a
CTS frame. The destination address specified in this CTS frame is the transmitting client's own medium
access control (MAC) address. All clients connected to the RF medium are required to listen to CTS
frames. A CTS frame is interpreted as a do not send command by all clients except by the one whose MAC
address is specified in the destination field.
When RTS-CTS is employed, clients must request access to the RF medium by sending an RTS to the
AP. The client refrains from accessing the medium and transmitting data until it receives a CTS from the
AP. A CTS command is interpreted as a do not send command when it is received by a client that did not
initiate the RTS. RTS-CTS requires more protocol overhead than CTS-only.
Usage Examples
The following example enables protection mode to automatically activate upon association of an 802.11b
client with an 802.11g AP. RTS-CTS is specified, but the rate is not. This means that the default rate of
11 Mbps will be used.
(config)#interface dot11ap 1/1 radio-type 802.11bg
(config-dot11ap 1/1-bg)#protection-mode auto type rts-cts
60000CRG0-35E
Sets the packet rate to 5.5 Mbps.
Sets the packet rate to 11 Mbps.
Command was introduced
Copyright © 2012 ADTRAN, Inc.
Radio Interface Command Set
2824
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