| ||Data Integrity|| |
| ||The condition that exists when data is unchanged from its source and has not been accidentally or maliciously modified, altered, or destroyed.|
| ||Data Link Layer|| |
| ||The data link layer is the 2nd of the seven-level OSI model. It responds to service requests from the network layer and issues service requests to the physical layer. The Data Link Layer provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the Physical Layer. Examples of data link protocols are HDLC and ADCCP for point-to-point or packet-switched networks and LLC for local area networks.|
| ||Datagram|| |
| ||A datagram is a self-contained packet,one which contains enough information in the header to allow the network to forward it to the destination independently of previous or future datagrams. Unlike with virtual circuit protocols, when datagrams are sent there are no call establishment or clearing procedures. Thus, the network may not be able to provide protection against loss, duplication, or misdelivery.|
| ||Delay|| |
| ||The amount of time by which an event is retarded.|
| ||Digital|| |
| ||A digital system is one that uses discrete values rather than a continuous spectrum of values, compared to analog. The word comes from the same source as the word digit: the Latin word for finger (counting on the fingers) as these are used for discrete counting. |
A digital signal is a discrete signal which has been sampled in amplitude in addition to time.
| ||DNS (Domain Name System)|| |
| ||The Domain Name System or DNS is a system that stores information about host names and domain names in a kind of distributed database on networks, such as the Internet. Most importantly, it provides an IP address for each host name, and lists the mail exchange servers accepting e-mail for each domain. |
The DNS provides a vital service on the Internet, because while computers and network hardware work with IP addresses to perform tasks such as addressing and routing, humans generally find it easier to work with host names and domain names, for example in URLs and e-mail addresses. The DNS therefore mediates between the needs and preferences of humans and of software.
| ||Duplex|| |
| ||In telecommunications, duplex means "two-way" when referring to communications channels.|
- A simplex channel is a one-way channel.
- A half-duplex channel is one that can carry information in both directions, but not at the same time.
- A full-duplex channel is a channel which can carry information in both directions at once.