Glossary Terms - D

Data Link Layer (Data Link Layer)
The OSI layer that is responsible for data transfer across a single physical connection, or series of bridged connections, between two Network entities. [Source: RFC 1208]
DECnet (DECnet)
Digital Equipment Corporation's proprietary network architecture. [Source: RFC 1208]
DARPA (Defense Advanced Research Projects Agency)
The U.S. government agency that funded the ARPANET. [Source: RFC 1208]
DCA (Defense Communications Agency)
. The government agency responsible for the Defense Data Network (DDN). [Source: RFC 1208]
DDN (Defense Data Network)
Comprises the MILNET and several other DoD networks. [Source: RFC 1208]
DSA (Directory System Agent)
The software that provides the X.500 Directory Service for a portion of the directory information base. Generally, each DSA is responsible for the directory information for a single organization or organizational unit. [Source: RFC 1208]
DUA (Directory User Agent)
The software that accesses the X.500 Directory Service on behalf of the directory user. The directory user may be a person or another software element. [Source: RFC 1208]
DCE (Distributed Computing Environment)
An architecture of standard programming interfaces, conventions, and server functionalities (e.g., naming, distributed file system, remote procedure call) for distributing applications transparently across networks of heterogeneous computers. Promoted and controlled by the Open Software Foundation (OSF), a consortium led by HP, DEC, and IBM. See ONC. [Source: RFC 1208]
domain (domain)
In the Internet, a part of a naming hierarchy. Syntactically, an Internet domain name consists of a sequence of names (labels) separated by periods (dots), e.g., "" In OSI, "domain" is generally used as an administrative partition of a complex distributed system, as in MHS Private Management Domain (PRMD), and Directory Management Domain (DMD). [Source: RFC 1208]
DNS (Domain Name System)
The distributed name/address mechanism used in the Internet. [Source: RFC 1208]
dotted decimal notation (dotted decimal notation)
The syntactic representation for a 32-bit integer that consists of four 8-bit numbers written in base 10 with periods (dots) separating them. Used to represent IP addresses in the Internet as in: [Source: RFC 1208]

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