D4 framing. See SF.
DAC. dual-attached concentrator. An FDDI or a CDDI concentrator capable of attaching to both rings of an FDDI or CDDI network. It can also be dual-homed from the master ports of other FDDI or CDDI concentrators.
DARPA. Defense Advanced Research Projects Agency. A U.S. government agency that funded research for and experimentation with the Internet. Evolved from ARPA, and then, in 1994, back to ARPA. See also ARPA.
DARPA Internet. An obsolete term referring to the Internet. See Internet.
DAS. dual attachment station. A device attached to both the primary and the secondary FDDI rings. Dual attachment provides redundancy for the FDDI ring; if the primary ring fails, the station can wrap the primary ring to the secondary ring, isolating the failure and retaining ring integrity. Also known as a Class A station. Compare with SAS.
database object. In general, a piece of information that is stored in a database. See DB connector.
data channel. See D channel.
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