Daemon Program

A utility program that runs on a TCP/IP server. Daemon programs run in the background, performing services such as file transfers, printing, calculations, searching for information, and many other tasks. This is similar to a TSR program in DOS. Daemons are fully supported by UNIX, however.

Daily Backup

A backup type that backs up all of the files that have been modified on the day that the daily backup is performed. The archive attribute is not set on the files that have been backed up.

DAP

See Directory Access Protocol.

DARPA (Defense Advanced Research Projects Agency)

The U.S. government agency that funded the ARPANET.

Data Access Objects (DAO)

A set of programmable objects that Microsoft Access developers use to manipulate data through Jet, the data-access engine for Access and other Microsoft desktop products.

Data Cache

SQL Server does its own caching of data to speed up access to databases. The size of the data cache can be indirectly manipulated by allocating more or less RAM to SQL Server.

Data Compression

The process of storing data in a form that takes less space than the uncompressed data.

Data Country Code

Part of an ATM address, the data country code contains the code for the country in which the ATM address is registered.

Data Encryption

The process of translating data into code that is not easily accessible to increase security. Once data has been encrypted, a user must have a password or key to decrypt the data.

Data Frames

Logical, structured packets in which data can be placed. The Data Link layer packages raw bits from the Physical layer into data frames. The exact format of the frame used by the network depends on the topology.

Data Link Control (DLC)

An obsolete network transport protocol that allows PCs to connect to older IBM mainframes and HP printers. See Transmission Control Protocol/Internet Protocol.

Data Link Layer

In the Open Systems Interconnection (OSI) model, the layer that provides the digital interconnection of network devices and the software that directly operates these devices, such as network adapters.

Data Mart

A database system concerned with live updates and new data, such as an online ordering system. See also Online Transaction Processing (OLTP).

Data Packet

A unit of data being sent over a network. A packet includes a header, addressing information, and the data itself. A packet is treated as a single unit as it is sent from device to device.

Data Service Unit (DSU)

A piece of telecommunications circuit terminating equipment that transforms digital data between telephone company lines and local equipment.

Data Source Name (DSN)

A user-created identifier used by ODBC to negotiate connections to any ODBC-compliant data source. A DSN consists of a server location and a driver name and can optionally contain a database name and authentication information. See also ODBC.

Data Transfer Rate

The data transfer rate determines how fast a drive or other peripheral can transfer data with its controller. The data transfer rate is a key measurement in drive performance.

Data Warehousing

Storage and querying of historical data, also referred to as decision-support systems. The main focus of data warehousing is the ability to quickly query existing data and perform complex analyses, usually looking for patterns or other relationships that are difficult to locate during the day-to-day operations of a company.

Database

A related set of data organized by type and purpose. The term also can include the application software that manipulates the data. The Windows Registry (a database itself) contains a number of utility databases such as user account and security information. See Registry.

Database File

In SQL Server, databases are stored on two types of database files. One file stores the actual data and indexes while the other file stores the transaction log. By default, the first data file has an .MDF extension. Additional data files have an .NDF extension. The transaction log files always have a default extension of .LDF.

Database Maintenance Plan Wizard

A wizard (step-by-step utility) provided with SQL Server that helps you schedule backups and perform database optimizations and consistency checking. This wizard can also automate and schedule these routine database maintenance tasks.

Database Management System (DBMS)

An environment created specifically for the purpose of working with databases. The term database management system usually refers to an electronic system or a computer program designed to work with databases. Microsoft Access and FoxPro are both examples of database management systems.

Database User

A SQL Server login ID that has been mapped into a particular database. Without a valid mapping, a login will not have access to a database.

Database Verification

Allows you to adjust the interval at which the consistency and integrity of a WINS or DHCP database is verified.

Datagram

A packet of information and associated delivery information, such as the destination address, that is routed through a packet-switching network.

Datagram Packet-Switched Network

A type of network on which messages are divided into a stream of separately addressed packets. Each packet is routed independently. The packets are reassembled at the destination address.

Datatype

A component of a SQL Server database that determines what kinds of data, such as character data, numeric data, or date/time data, can be stored in a column. A column can hold data of only a single datatype.

DB-Library

A set of functions and connectivity programs that allow clients to communicate programatically with database engines. A database engine is responsible for processing queries, maintaining data, ensuring data consistency, and providing a mechanism for backup and restoration.

DBCC (Database Consistency Checker)

SQL Server commands used to check the consistency of databases. These commands are generally used to gather information about the status of a database rather than to make changes to it.

DBO (Database Owner)

In SQL Server, a user who has full permissions in a particular database. This includes the ability to back up and restore the database and transaction log. The SA is also considered the DBO of every database. The DBO is specified through the sp_changedbowner stored procedure.

DBOO (Database Object Owner)

In SQL Server, a user who creates a particular database object. The DBOO has all rights on that object, including the right to allow other database users to use the object.

D Channel

A telecommunications term which refers to the ISDN channel in which the control and signalling information is carried. The bit rate of the D channel of a basic rate interface is 16 kbit/s, whereas it amounts to 64 kbit/s on a primary rate interface.

DDE

See Dynamic Data Exchange.

DDR

See Demand-Dial Routing.

Debugging Mode

A Windows 2000 Advanced Option menu item that runs the Kernel Debugger, if that utility is installed. The Kernel Debugger is an advanced troubleshooting utility.

Decentralized Management

A management model in which resources are managed locally.

Decoding

The process of translating a message from a transmittable standard form to the native form of the recipient.

Decryption

The conversion of encrypted data back into its original form. See also Encryption.

Dedicated IP Address

The IP address used by the Network Load Balancing service of Windows to distinguish the individual hosts of a cluster.

Dedicated Line

A transmission medium that is used exclusively between two locations. Dedicated lines are also known as leased lines or private lines.

Dedicated Server

A computer that functions only as a server and is not used as a client or workstation.

Default

A SQL Server object assigned to a column or user-defined datatype in a table. If no data is entered, the default value will be used. This can also refer to the default database that is assigned to a SQL Server login ID. If the login attempts to run a query without specifying a database, the query will be applied to the default database.

Default Gateway

A TCP/IP configuration option that specifies the gateway that will be used if the network contains routers.

Default Response Rule

IP filtering rule that governs what the IP filtering stack does when no other more explicit filter rule applies.

Default Route

The route packets take when there is no explicit route; if a router encounters a packet bound for some remote network whose route cannot be resolved in the routing table, it takes the default route.

Default Shares

Resources shared by default when Windows is installed. See Share, Resource.

Default Subnet Mask

Network IDs and host IDs within an IP address are distinguished by using a subnet mask. The default subnet mask is assigned to a Class A, B, or C address. These addresses are characterized by 8, 16, or 24 bits to specify the network number in the address.

Delegated Domain

The name of the domain for which you want to delegate authority to another DNS server.

Delegated Namespace

Using a delegated namespace resembles creating separate public and private namespaces. However, in this case you are creating a single subdomain within the namespace in whiUsing a delegated namespace resembles creating separate public and private namespaces. However, in this case you are creating a single subdomain within the namespace in which the DNS servers for the namespace will reside, rather than dividing the namespace into public and private portions. For instance, for the contoso.com domain, the delegated namespace may be corp.contoso.com. In this model, you would enable internal clients to resolve both internal and external DNS namespaces, but deny access to the internal namespace to external clients. A separate DNS server or servers is required for the delegated internal domain.

Delegation

The process by which a user who has higher-level security permissions grants certain permissions over Active Directory objects to users who are lower-level security authorities. Delegation is often used to distribute administrative responsibilities in a network environment.

Delegation of Control Wizard

A Windows tool used for delegating permissions over Active Directory objects. See also Delegation.

Delegation Resource Record

Used to locate the authoritative DNS servers for a delegated zone. These records “glue” zones together and provide an effective path for delegation and referral that other DNS servers can follow in the process of resolving a name. Commonly used with stub zones.

Demand-Dial Interface

A network interface that routes packets over a connection that is established only when there is traffic to pass over it. These interfaces are usually built with dial-up connections.

Demand-Dial Routing (DDR)

A routing mechanism that allows a user to utilize existing telephone lines, or Public Switched Telephone Networks, to form a WAN instead of using dedicated connections. Typically implemented by users who do not need a permanent, continuous link between sites, the connection becomes active only when data is sent to the remote site. When no data has been sent over the link for a specified length of time, the link is disconnected.

Demand-Dial Routing Connections

Support for both inbound connections and outbound connections for a RAS server. Resources located across a WAN connection requiring a modem, or other similar dialing device, can be automatically connected by the system upon request for those items.

Demarc (D-mark, Demarcation)

The point at which the carrier from your provider terminates and is then connected to your internal network.

Demilitarized Zone (DMZ)

A network that sits between the secured private network and an unsecured external network, typically the Internet, providing an additional layer of security.

Denial-of-Service Attack

A system shutdown caused by too many requests or too much data. Occurs when a computer system receives so many service requests or so much data that it becomes overwhelmed and effectively shuts down.

Departmental Model

The traditional method of managing a business. The basics of the departmental model are quite simple – look at the tasks that make up the business processes of a company, group them according to function, and manage each group.

Desktop

A directory that the background of the Windows Explorer shell represents. By default, the Desktop includes objects that contain the local storage devices and available network shares. Also a key operating part of the Windows graphical interface.

Desktop Information Manager

An application that can be used to manage may aspects of a user’s activities, such as reading and sending e-mail, accessing calendar and scheduling information, and task management.

Destination Service Access Point (DSAP)

Destination Service Access Point (DSAP) is the individual or group address for the address into the upper layers of the network protocol stack. DSAP is an eight bit field that allows the LLC layer to keep track of multiple connections across an IEEE 802 LAN environment.

Destination Set

External computers of directories you wish to either allow or deny access to or from internal ISA Server clients.

Device Driver

Software that allows a specific piece of hardware to communicate with the Windows operating system.

Device Manager

A Windows utility used to provide information about the computer’s configuration.

Dfs Root

An object in the Microsoft Active Directory system used for sharing files and folders across network. DFS root is the starting point of the DFS namespace.

Dfs Shared Folder

Files or folders in the DFS namespace that are shared by users with proper permissions. Shared folders can exist at the root level (domain-based DFS only) or be referred to by DFS links.

DHCP

See Dynamic Host Configuration Protocol.

DHCP Allocator

An addressing component that is a simplified DHCP server, which assigns an IP address, a subnet mask, a default gateway, and the IP address of a DNS server.

DHCP Authorization

The process of enabling a DHCP server to lease addresses by registering the server in Active Directory.

DHCP Discover Message

Message broadcast by a DHCP client that is looking for a nearby DHCP server; the discover message contains the hardware MAC address and NetBIOS name of the client, which the server can use to direct the request.

DHCP Integration

Feature that allows you to pass out addresses to DHCP clients while still maintaining the integrity of your DNS services.

DHCP Lease Request

Request sent by a DHCP client for assignment of an IP address (and related parameters) from a DHCP server.

DHCP Relay Agent

To enable DHCP on a multisegment network, you can use a DHCP relay agent or proxy to forward requests.

DHCP Server

A server configured to provide DHCP clients with all of their IP configuration information automatically.

DHCPACK

An acknowledgement message sent by the DHCP server to the client after the server marks the selected IP address as leased.

DHCPNACK

A negative acknowledgement sent by the DHCP server to the client. This generally occurs when the client is attempting to renew a lease for its old IP address after it has been reassigned.

Dialing Rules

Allow you to tell Dial-Up Networking what country and region you are in so that it knows to add the appropriate long-distance codes, area codes, and calling card numbers when it is dialing.

Dial-On-Demand Routing (DDR)

A technique whereby a host or router will automatically initiate a dial-up connection over an ISDN or regular public switched telephone network line when network access is required, and close the connection when no more data needs to be transmitted or received. The line will only be used when needed, which reduces costs where circuit-switched (telephone) connections are billed by the minute.

Dial-Up Connections

Data Link layer digital connections made via modems over regular telephone lines. The term dial-up refers to temporary digital connections, as opposed to leased telephone lines, which provide permanent connections. See Data Link Layer, Public Switched Telephone Network, Modem.

Dial-Up Networking

A service that allows remote users to dial into the network or the Internet (such as through a telephone or an ISDN connection).

Dialup Group

A Windows 2000 special group that includes users who log on to the network from a dialup connection.

Differential Backup

A backup type that copies only the files that have been changed since the last normal backup (full backup) or incremental backup. A differential backup backs up only those files that have changed since the last full backup, but does not reset the archive bit.

Digest

A unique mathematical value calculated by a special type of algorithm called a hashing algorithm or a message authentication algorithm from the actual message contents. The digest is then encrypted using the private key and either added to the end of the message or sent as a separate file attachment.

Digital Certificates

The passports of the electronic world. Like your passport booklet, which contains the unique passport ID number, a digital certificate serves as a carrying case for a public key. A certificate contains the public key and a set of attributes, such as the key holder’s name and e-mail address.

Digital Data

Data that uses 1′s and 0′s to store information.

Digital Intel Xerox (DIX)

Another term for the AUI connector. See also Attachment User Interface.

Digital Line

A data or voice network interconnectivity medium that supports digital signaling. See also Digital Signaling.

Digital Signaling

Data transmission in the form of discrete units (on or off, 1 or 0, and so on).

Digital Signatures

An electronic signature used to authenticate the sender’s identity as well as to ensure that the message was not altered in transit.

Digital Versatile Disc (DVD)

A disk standard that supports up to 4.7 GB of data. One of DVD’s strongest features is backward compatibility with CD-ROM technology, so that a DVD drive can play CD-ROMs. Formerly known as Digital Video Disk.

Digital Video Disk-Recordable

A DVD disk with a recordable format. A DVD-R typically has a storage capacity of 4.71 GB (or 4.38 GiB), although the capacity of the original standard developed by Pioneer was 3.95 GB (3.68 GiB). Both values are significantly larger than the storage capacity of its optical predecessor, the 700 MB CD-R – a DVD-R has 6.4 times the capacity of a CD-R. Pioneer has also developed an 8.54 GB dual layer version, DVD-R DL, which appeared on the market in 2005.

Directed Broadcast

Generally considered more network friendly than an all-routes broadcast, a directed broadcast limits itself to the local network that you specify. Routers forward this request to the destination network where it becomes a local broadcast. Intermediate networks do not see this packet as a broadcast.

Directives

Additional information contained in a W3C-format log file that records version, date, and logged fields as well as the actual data.

Directories

In a file system, directories are containers that store files or other directories. Mass storage devices have a root directory that contains all other directories, thus creating a hierarchy of directories sometimes referred to as a directory tree. See File, File System.

Directory Access Protocol (DAP)

The X.500 protocol designed to allow access to X.500-compliant directories. Its major failing was that it was proprietary in nature – any given implementation would work only with a specific brand of directory. For this reason, it is not used much in today’s world.

Directory Replication

The process of copying a directory structure from an export computer to an import computer(s). Anytime changes are made to the export computer, the import computer(s) is automatically updated with the changes.

Directory Replication Bridgehead Server

The Exchange server designated as the server that will send site directory information to another site. Only one server in a site can be assigned to replicate information with each remote site. There can be more than one directory replication bridgehead server in a site, but each must connect with a unique remote site. One server can, however, perform directory replication with multiple remote sites.

Directory Services Restore Mode

A special boot mode for Windows domain controllers. The Directory Services Restore mode is used to boot a domain controller without starting Active Directory services. This enables system administrators to log on locally to restore or to troubleshoot any problems with the Active Directory.

Directory Synchronization

A process that keeps the information in two separate directories synchronized; that is, changes made to information in one directory will be propagated automatically to the other.

Directory Synchronization Protocol

The MS Mail protocol used to synchronize directory information between MS Mail postoffices. One server is designated as the dirsync server and the other servers are designated as dirsync requestors. the dirsync server maintains the master copy of a network’s directory. The dirsync requestors send any new directory information to the dirsync server, and request a copy of the master directory. See Dirsync Requestor and Dirsync Server.

Dirsync Requestor

A type of MS Mail postoffice that sends its new directory information to the designated dirsync server, and requests a copy of the master directory from the dirsync server. See also Directory Synchronization Protocol, T1, and T3.

Dirsync Server

A type of MS Mail postoffice that maintains the master copy of a network’s MS Mail directory information. It also responds to requests by sending a copy of the master directory to dirsync requestors. See also Directory Synchronization Protocol and T2.

Discard Eligible

The portion of bandwidth that exceeds the Committed Information Rate and is considered expendable if necessary.

Discretionary Access Control List (DACL)

Part of an object’s security descriptor that grants or denies permission for access of an object to specific users and groups. Only an object’s owner can change permissions in the object’s DACL.

Discussion Thread

A collection of postings to a public folder related to a single subject.

Disinfection

A function of an antivirus program which attempts to remove and disinfect infections on the computer system including viruses, worms and Trojan horses. Disinfection in antivirus programs may also detect and remove unwanted applications as well.

Disk Administrator

Graphical utility used to manage disks.

Disk Cleanup

A Windows utility used to identify areas of disk space that can be deleted to free additional hard disk space. Disk Cleanup works by identifying temporary files, Internet cache files, and unnecessary program files.

Disk Defragmentation

The process of rearranging the existing files on a disk so that they are stored contiguously, which optimizes access to those files.

Disk Defragmenter

A Windows utility that performs disk defragmentation.

Disk Duplexing

Disk mirroring with two separate controllers for better performance and reliability. See also Disk Mirroring

Disk Image

An exact duplicate of a hard disk, used for automated installation. The disk image is copied from a reference computer that is configured in the same manner as the computers on which Windows will be installed.

Disk Management

A Windows graphical tool for managing disks and volumes.

Disk Mirroring

The process of keeping an exact duplicate of data on two different partitions located on different physical drives. Used for fault tolerance. See also Disk Duplexing.

Disk Partitioning

The process of creating logical partitions on the physical hard drive.

Disk Quota Policies

Policies used to specify how much disk space can be allocated by users.

Disk Quotas

A Windows feature used to specify how much disk space a user is allowed to use on specific NTFS volumes. Disk quotas can be applied for all users or for specific users.

Disk Striping

Data that is stored across partitions of identical size on different drives. Also referred to as RAID 0. See also Redundant Array of Inexpensive Disks.

Disk Striping with Parity

Disk striping with parity distributed across the stripe set for fault tolerance features. Also referred to as RAID 5. See also Stripe Set, Redundant Array of Inexpensive Disks.

Distance-Vector Routing

A method of route discovery in which each router on the network broadcasts the information contained in its routing table. The other routers then update their routing tables with the broadcast information they receive.

Distance-Vector Routing Algorithm

An algorithm used by routing protocols to discover routes on an interconnected network. The primary distance-vector routing algorithm is the Bellman-Ford algorithm. Another type of routing algorithm is the link-state approach. Routing protocols that use distance-vector routing include RIP (Routing Information Protocol), Cisco’s IGRP (Internet Gateway Routing Protocol), and Apple’s RTMP (Routing Table Maintenance Protocol). The most common link-state routing protocol is OSPF (Open Shortest Path First).

Distinguished Name

The fully qualified name of an object within a hierarchical system. Distinguished names are used for all Active Directory objects and in the Domain Name System (DNS). No two objects in these systems should have the same distinguished name.

Distributed Authoring and Versioning (DAV)

An IETF standard set of platform-independent extensions to HTTP that allows users to collaboratively edit and manage files on remote Web servers. DAV features XML properties on metadata, locking – which prevents authors from overwriting each other’s changes – namespace manipulation and remote file management.

Distributed Caching

A system by which a group of ISA Servers is configured as an array and is then managed as a single logical entity. These servers share the cached content among all the servers in the array, thereby distributing the content among the array members. Distributed caching also allows for both load balancing and fault tolerance of the cache.

Distributed File System

A method of storing and accessing files based in a client/server architecture. In a distributed file system, one or more central servers store files that can be accessed, with proper authorization rights, by any number of remote clients in the network. Much like an operating system organizes files in a hierarchical file management system, the distributed system uses a uniform naming convention and a mapping scheme to keep track of where files are located. When the client device retrieves a file from the server, the file appears as a normal file on the client machine, and the user is able to work with the file in the same ways as if it were stored locally on the workstation. When the user finishes working with the file, it is returned over the network to the server, which stores the now-altered file for retrieval at a later time.

Distributed Transaction Coordinator (DTC)

The DTC helps coordinate queries that are run between two or more SQL Servers. The DTC ensures that the transaction is performed simultaneously on both servers, or not at all.

Distribution Group

A collection of Active Directory users that are used primarily for e-mail distribution.

Distribution Server

A network server that contains the Windows operating system distribution files that have been copied from the distribution CD. Clients can connect to the distribution server and install a Windows operating system over the network.

DLC

See Data Link Control.

DNS

See Domain Name Service.

DNS Client

The network node that needs to resolve a hostname to an IP address. This is also commonly referred to as the resolver.

DNS Namespace

A hierarchical network naming structure that is designed to resolve hostnames to IP addresses. Typical DNS names within a namespace are hierarchical, ranging from most specific on the left to least specific on the right (e.g., server1.mycompany.com).

DNS Proxy

A technology used with DHCP servers that allows them to register DNS data for the computers that they issue leases to. The DHCP server acts as a proxy for the DNS server. TA technology used with DHCP servers that allows them to register DNS data for the computers that they issue leases to. The DHCP server acts as a proxy for the DNS server. The DHCP server must be registered with Active Directory through the DnsProxyUpdate group.

DNS Server

A server that uses DNS to resolve domain or host names to IP addresses.

DNS Server, Caching-Only

A DNS server that is not the authority for any specific zone but can resolve DNS queries. Caching-only DNS servers are used to improve performance.

DNS Server, Master

A DNS server that is responsible as an authority for name resolution within a DNS zone. Each DNS zone can have only one master DNS server.

DNS Server, Primary

A DNS Server that is authoritative for a zone and that is able to receive updates of DNS information.

DNS Server, Secondary

A DNS server that is used to resolve DNS names to TCP/IP addresses. Secondary servers contain a read-only copy of the DNS database.

DNS Zone

The portion of the DNS namespace that is contained in a single file.

Docking Station

A hardware device that allows portable computers to connect with other devices with little or no effort. Most docking stations allow a user to connect their laptop computer to a docking station and get the added support of other peripherals such as other drives, a monitor, a printer, a scanner, speakers, etc., connected to it.

DoD Networking Model

A four-layer conceptual model describing how communications should take place between computer systems. The four layers are Process/Application, Host-to-Host, Internet, and Network Access. DoD is the acronym for Department of Defense, the government agency that provided the original funding for the development of the TCP/IP protocol suite.

Domain

In Microsoft networks, an arrangement of client and server computers referenced by a specific name that shares a single security permissions database. On the Internet, a domain is a named collection of hosts and subdomains, registered with a unique name by the InterNIC.

Domain Controller

A Windows server computer that includes a copy of the Active Directory data store. Domain controllers contain the security information required to perform services related to the Active Directory.

Domain Forest

A collection of one or more domain trees with a common schema and implicit trust relationships between them. This arrangement would be used if you have multiple root DNS addresses.

Domain Local Group

An Active Directory security or distribution group that can contain Universal groups, Global groups, or accounts from anywhere within an Active Directory forest.

Domain Name

A name that identifies one or more IP addresses, such as microsoft.com. Domain names are used in URLs to identify particular Web pages.

Domain Name Server

An Internet host dedicated to the function of translating fully qualified domain names into IP addresses.

Domain Name Service (DNS)

The TCP/IP network service that translates fully qualified domain names (or host names) into IP addresses.

Domain Naming Master

The Active Directory domain controller that is responsible for handling the addition and removal of domains within the Active Directory environment.

Domain Policies

Policies applied at the domain level that allow administrators to control what a user can do after logging on. Domain policies include audit policies, security option policies, and user right policies. These policies are set through Domain Controllers Policy.

Domain Restructure

The process of redesigning your existing domains to match the business needs of your environment.

Domain Tree

Also referred to as forests and trees, the domain tree is the group of domains in Windows Active directory that all have the same Domain Name Server (DNS). For example, contoso.com, the top domain also referred to as the parent and its child domains help.contoso.com and support.contoso.com.

Domain User

A user account that is stored in the Windows Active Directory’s central database. A domain user account provides a user with access to domain-based resources. Also called an Active Directory user account.

Domain User Account

A user account that is stored in the Windows Active Directory’s central database. A domain user account can provide a user with a single user account for a network. Also called an Active Directory user account.

Double-Byte Character Set

A character set which uses 16-bit (two-byte) characters rather than 8-bit (one-byte) characters. Using double-byte characters expands the possible number of combinations of 1s and 0s from 256 (as in ASCII) to 65,536 (or 256 x 256). Double-byte character sets are needed for such languages as Japanese, Chinese, and Korean, which have many characters. These character sets must be used with hardware and software that supports the double-byte format.

Downstream Servers

When ISA Servers are configured in a chain, one server passes information requests to another server that is connected to the Internet; the server that is closer to the client and removed from the Internet is considered to be downstream.

Drive

See Hard Disk Drive.

Drive Letter

A single letter assigned as an abbreviation to a mass-storage volume available to a computer.

Driver

A program that provides a software interface to a hardware device. Drivers are written for the specific devices they control, but they present a common software interface to the computer’s operating system, allowing all devices of a similar type to be controlled as if they were the same.

Driver Signing

A digital imprint that is Microsoft’s way of guaranteeing that a driver has been tested and will work with the computer.

Dropper

A program (malware component) that has been designed to “install” some sort of malware (virus, backdoor, etc) to a target system. The malware code can be contained within the dropper (single-stage) in such a way as to avoid detection by virus scanners or the dropper may download the malware to the target machine once activated (two stage). There are two major types of droppers, those that do not require user interaction which perform through the exploitation of a system by some vulnerability and those that require user interaction by convincing the user that it is some legitimate or benign program. A dropper which installs a malware program to memory only is sometimes called an injector.

Dr. Watson

A Windows utility used to identify and troubleshoot application errors.

DRWTSN32

The command used to access the Dr. Watson utility.

DSProxy

The Exchange component that can proxy (and refer) Messaging Application Programming Interface (MAPI) directory service requests from Outlook clients to Active Directory for Address Book lookup and name resolution.

Dual-Booting

The process of allowing a computer to boot more than one operating system.

Dumb Terminal

A workstation consisting of a keyboard and monitor, used to put data into the computer or receive information from the computer. Dumb terminals were originally developed to be connected to computers running a multi-user operating system so that users could communicate directly with them. All processing is done at and by the computer, not the dumb terminal. In contrast, a smart terminal contains processing circuits which can receive data from the host computer and later carry out independent processing operations.

Dump Device

See backup device.

DUN

See Dial-Up Networking.

Duplexing

A method of using a second hard drive with a second hard drive controller to provide fault tolerance.

DVD

See Digital Versatile Disc.

Dynamic Backup

A type of backup that allows you to back up your SQL Server databases while they are in use. Users can stay connected to the server and run most queries while a dynamic backup is in progress.

Dynamic Data Exchange (DDE)

A method of interprocess communication within the Microsoft Windows operating systems.

Dynamic Disk

A Windows disk-storage technique. A dynamic disk is divided into dynamic volumes. Dynamic volumes cannot contain partitions or logical drives, and they are not accessible through DOS. You can size or resize a dynamic disk without restarting Windows. Dynamic disks are accessible only to Windows systems.

Dynamic DNS

Allows Windows clients to update host information in the DNS database files automatically.

Dynamic DNS (DDNS) Standard

The RFC that specifies how Dynamic DNS needs to be implemented to ensure interoperability between various vendors’ DDNS products.

Dynamic Host Configuration Protocol (DHCP)

A method of automatically assigning IP addresses to client computers on a network.

Dynamic Link Library (DLL)

A set of modular functions that can be used by many programs simultaneously. There are hundreds of functions stored with DDLs.

Dynamic Packet Filtering

The process by which ports are opened and closed on the firewall only in response to client requests for services or applications.

Dynamic Route Selection

Uses the cost information that is continually being generated by routing algorithms and placed in routing tables to select the best route for each packet. As network conditions change, the router can select the best path.

Dynamic Routing

Can discover its surroundings by finding and communicating with other nearby routers.

Dynamic Storage

A Windows disk-storage system that is configured as volumes. Windows dynamic storage supports simple volumes, spanned volumes, and striped volumes.