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Professional Access Point
Administrator Guide
Glossary - 307
BSSID
In Infrastructure Mode, the Basic Service Set Identifier (BSSID) is the 48-bit MAC address of the wireless
interface of the Access Point.
C
CCMP
Counter mode/CBC-MAC Protocol (CCMP) is an encryption method for 802.11i that uses AES. It employs
a CCM mode of operation, combining the Cipher Block Chaining Counter mode (CBC-CTR) and the
Cipher Block Chaining Message Authentication Code (CBC-MAC) for encryption and message integrity.
AES-CCMP requires a hardware coprocessor to operate.
CGI
The Common Gateway Interface (CGI) is a standard for running external programs from an HTTP server. It
specifies how to pass arguments to the executing program as part of the HTTP request. It may also define
a set of environment variables.
A CGI program is a common way for an HTTP server to interact dynamically with users. For example, an
HTML page containing a form can use a CGI program to process the form data after it is submitted.
Channel
The Channel defines the portion of the radio spectrum the radio uses for transmitting and receiving. Each
802.11 standard offers a number of channels, dependent on how the spectrum is licensed by national and
transnational authorities such as the Federal Communications Commission (FCC), the European
Telecommunications Standards Institute (ETSI), the Korean Communications Commission, or the
Telecom Engineering Center (TELEC).
CSMA/CA
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) is a low-level network arbitration/
contention protocol. A station listens to the media and attempts to transmit a packet when the channel is
quiet. When it detects that the channel is idle, the station transmits the packet. If it detects that the channel
is busy, the station waits a random amount of time and then attempts to access the media again.
CSMA/CA is the basis of the IEEE 802.11e Distributed Control Function (DCF). See also RTS and CTS.
The CSMA/CA protocol used by 802.11 networks is a variation on CSMA/CD (used by Ethernet networks).
In CSMA/CD the emphasis is on collision detection whereas with CSMA/CA the emphasis is on collision
avoidance.
CTS
A clear to send (CTS) message is a signal sent by an IEEE 802.11 client station in response to an request
to send (RTS) message. The CTS message indicates that the channel is clear for the sender of the RTS
message to begin data transfer. The other stations will wait to keep the air waves clear. This message is a
part of the IEEE 802.11 CSMA/CA protocol. (See also RTS.)