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Appendix B: Glossary
CISPR
: See Special International Committee on Radio Interference.
class of service (COS, CoS)
: A field in the packet’s IP header that specifies traffic priorities. COS operates at the data-link layer
(layer 2) of the protocol stack.
Also see Differentiated Services, quality of service, type of service.
code-division multiple access, code-division multiplexing (CDMA, CDM)
: A wireless technology that uses spread-spectrum
communication. To send a call, CDM uses several frequencies along the spectrum of its radiofrequency band. When the call is
received, it is reassembled.
Compare time-division multiplexing, wavelength-division multiplexing.
combined cryptography
: (Also called hybrid cryptography.) A common practice of using asymmetric encryption and symmetric
encryption together.
For example, to encrypt a message:
• A sender might create a secret key and use it for symmetric encryption of a message.
• Then the sender might use asymmetric encryption (choosing the recipient’s public key or the sender’s private key) to package
the encrypted message and its secret key together as a single encrypted document.
NOTE: The recipient’s public key is the safer choice, because no one except the recipient should know the counterpart private key.
To decrypt the message:
• The recipient uses the counterpart in the key pair chosen by the sender (that is, the recipient’s private key or the sender’s public
key) to open the document. That decryption reveals the secret key and the still-encrypted message.
• Then the recipient uses the secret key to decrypt the message.
Comité consultatif international téléphonique et télégraphique (CCITT)
: A former French name for the International
Telecommunication Union, Telecommunication Standardization Sector.
(The equivalent former English name was the International Telegraph and Telephone Consultative Committee.)
Comité européen de normalisation (CEN)
: The French name for the European Committee for Standardization.
Comité international spécial des perturbations radioélectriques (CISPR)
: The French name for the Special International
Committee on Radio Interference.
confidentiality
: Privacy of communication—that is, the principle that a party that is not intended to know the content of a trans-
mission will not be able to determine the content of the transmission. The principal method used for safeguarding confidentiality
is encryption.
connectionless (protocol)
: A general term for protocols wherein devices do not establish a defined route for data transmission.
Instead, the header of each datagram (packet) contains the packet's destination address. A router looks at each packet’s header
and sends that packet on the best route toward its destination.
Because there is no specified route for transmissions, individual packets in a transmission can travel over different routes to the
destination. Compare connection-oriented.
connection-oriented (protocol)
: A general term for protocols wherein devices must establish a defined route for data transmis-
sion. Each packet in the transmission must travel over the defined route to the destination. Compare connectionless.
connection to remote office
: See teleworking.
cookie
: A cipher, generated and assigned by the host, that identifies clients without using comprehensive authentication. As used
in IKE, cookies conserve CPU resources yet offer some protection against replay attacks.
COS
: See class of service.
CRC
: See cyclic redundancy check.
