D

DARPA

See Defense Advanced Research Projects Agency (DARPA).

Data Encryption Standard (DES)

A non-trivial algorithm for encrypting data, classified as a munition by the United States Department of Commerce and Department of State.

data marshaling, data unmarshaling

The conversion of data back and forth between some local format and a common interchange format. Marshaled data is in the canonical eXtended Data Representation (XDR) format Abstract Syntax Notation One (ASN.1).

database

A collection of data organized for rapid search and retrieval by a computer.

database administrator (DBA)

An administrator of a database. This person is responsible for system tuning as well as the structure of the tables within the database, the number of instances to run, and other parameters. See also system administrator.

DBA

See database administrator (DBA).

DCE

See Distributed Computing Environment (DCE).

D-channel

A dedicated data channel for Integrated Services Digital Network (ISDN) configuration and set-up.

DCS

See Digital Cross-connect System (DCS)

Defense Advanced Research Projects Agency (DARPA)

The central research and development organization for the United States Department of Defense. It manages and directs selected basic and applied research and development projects for the Department, and pursues research and technology where risk and payoff are both very high and where success may provide dramatic advances for traditional military roles and missions and dual-use applications.

DEL

See Dialog Editing Library (DEL).

demilitarized zone (DMZ)

An area of a network, typically between the internal corporate network and either the external Internet or a partner, vendor, or client, usually between firewalls, providing some service or services. Part of a security system. See also firewall.

demux

See multiplex.

DES

See Data Encryption Standard (DES).

desktop

A display of one or more icons representing system resources.

Desktop Commands (DTC)

Commands used in the Advanced Development Environment (ADE) to manipulate a dialog instance.

DFS

See distributed file system (DFS).

DHC

See Dynamic Host Configuration (DHC).

DHCP

See Dynamic Host Configuration Protocol (DHCP).

dialog

A two-way communication link between an administrator and one or more TME resources.

Dialog Editing Library (DEL)

A library of C functions that permits dynamic, persistent creation and editing of dialog descriptors at run-time. See also Advanced Development Environment (ADE).

Dialog Specification Language (DSL)

Provides the dialog layout and interaction for handling application output and input. See gadget.

Digital Cross-connect System (DCS)

Pronounced "dax;" a digital version of or replacement for the analog data center patch panels.

Digital Private Network Signalling System (DPNSS)

A Common Channel Signalling (CCS) protocol used in telecommunications networks.

Digital Subscriber Line (DSL)

A high-speed digital network connection, usually between a home or small business and a telecommunications vendor, providing an always-up direct connection to an Internet Service Provider (ISP). It can be either asymmetric, where the upstream and downstream speeds are dissimilar, or symmetric, where the upstream and downstream speeds are the same.

DII

See Dynamic Invocation Interface (DII).

directive

(Security.) Specific actions to be taken and directions to be followed in implementing a policy. Adherence to directives is mandatory for users.

dirty

Not clean. A filesystem is dirty if it is in use or if there is no guarantee that the file system structure is static.

Disk Operating System (DOS)

The term DOS can refer to any operating system, but it is most often used as a shorthand for Microsoft's MS-DOS. Originally developed by Microsoft for IBM, MS-DOS was the standard operating system for IBM-compatible personal computers.

Disk Suite

A product from Sun Microsystems that allows the kernel to treat multiple distinct disk partitions as larger logical partitions (up to one terabyte per logical partition). It also allows for mirroring data, or storing data on multiple partitions simultaneously.

DISOSS

See Distribution Office Support Systems (DISOSS).

Distance Vector Multicast Routing Protocol (DVMRP)

A non-hierarchical, non-scaling multicast routing protocol, defined in RFC 1075.

Distributed Computing Environment (DCE)

An OSF product. A windowing environment similar to Motif.

distributed file system (DFS)

A file system that is distribtued across multiple geographic sites yet which appears to be a single local file system to the user. See also Andrew File System (AFS), Institutional File System (IFS).

Distribution Office Support Systems (DISOSS)

The IBM SNA electronic mail routing architecture for their mainframes. A distributed electronic mail system.

diversely routed

A network is diversely routed if there are multiple routes from point A to point B.

DMZ

See demilitarized zone (DMZ).

DNS

See Domain Name Service (DNS).

DNS record types

The domain name record types are:

A	Address, specifying the IP address
CNAME	Canonical name, an alias pointing to the true name of the host. Requires its right hand side to have an A record.
HINFO	Host information, detailed information about the specific host, such as location or operating system version.
LOC	Location, specifies the geographical location of the host.
MX	Mail exchange, specifies that the host on the left side will accept mail for the host on the right hand side at the priority shown (lower is preferred).
NS	Name server, specifies a host that will act as a domain name server for the specified domain.
PTR	Pointer, used to provide reverse lookups.
RP	Responsible person, the contact information for the specified domain.
SOA	Start of authority, the meta information for the specified zone. Contains email information, a serial number, and the time to live values. The specific format is defined in RFC 2181.
TXT	Text, a comment on the record. Otherwise ignored.
WKS	Well-known services, lists those services for a host. Allows for mnemonics (http, smtp, telnet) instead of specifying port numbers (80, 25, 21).

domain

1. The trailing portion of a fully qualified host address, typically in an e-mail context. See fully qualified domain name (FQDN).
2. A level in a NetInfo hierarchy. See NetInfo.
3. An organization of machines (clients, master servers, and slave servers) and maps in NIS. See Network Information Service (NIS).
4. A section of the Internet name space. See Domain Name Service (DNS).

domain level

A level in a NetInfo domain hierarchy. See NetInfo.

Domain Name Service (DNS)

A UDP protocol (defined in RFC 2181) for resolving names to IP addresses and vice versa. This leads to a hierarchical host naming structure which gives each computer on a network a unique name. See also fully qualified domain name (FQDN), resolver.

DOS

See Disk Operating System (DOS).

DPNSS

See Digital Private Network Signalling System (DPNSS).

drag-and-drop

The action of dragging an item with the mouse from one location to another, and releasing the mouse button at the destination.

DS0, DS1, DS3

Indicators of speed of data transfer over telecommunications lines, where:

DS0	A single 64 Kb/s channel.
DS1	A T1 line (1.544 Mb/s), or 24 DS0s.
DS3	A T3 line (45 Mb/s), or 28 DS1s.

The errors (if you do the math) are due to clocking information and overhead in managing the multiplexing of the channels on the fiber.

DSL

1. See Dialog Specification Language (DSL).
2. See Digital Subscriber Line (DSL).

DTC

See Desktop Commands (DTC).

DVMRP

See Distance Vector Multicast Routing Protocol (DVMRP).

Dynamic Host Configuration (DHC)

A task force or group within the Internet Engineering Task Force (IETF) which developed the Dynamic Host Configuration Protocol (DHCP) to supercede the aging Boot Protocol (BOOTP).

Dynamic Host Configuration Protocol (DHCP)

A superset of the Boot Protocol (BOOTP) which offers greater flexibility for IP address allocation. It provides the standard BOOTP-like method as well as automatic (long-term) or dynamic (short-term) allocation of IP addresses from a pool of available addresses.

Dynamic Invocation Interface (DII)

Used by a client to dynamically build a request to be sent to a server.