The following glossary defines 290 terms related to the IT Industry.  
Please do not reproduce without permission.

D Channel

The ISDN signaling channel. Runs at 16 or 64 Kbps.

Data transfer

In Web hosting, the total size of files transferred by an account in a month.  Sites with a lots of graphics, downloads, or streaming audio or video and a lot of visitors will require plans with more available transfer.

Database

Data in a structured format stored on a web server.  Most popular type is a relational database.  The most common query (information retrieval) language for relational databases is SQL.  Linux-based hosts most commonly include MySQL database and Windows NT-based hosts usually include Access or MS SQL databases.

Dedicated Server

Similar to co-location, except that you lease or rent hardware from a Web host.  The main advantage over co-location is easier upgrade and usually better support.  Getting a dedicated server or co-locating is necessary for sites that outgrow shared servers because they use a lot of bandwidth and resources or they require total control over software environment.  

DES

Data Encryption Standard - an U.S. government approved cipher. It is easy to break in its simplest form, but used multiple times with key of at least 128 bits provides good security.

DHCP

(Dynamic Host Configuration Protocol). An automated way of obtaining an IP address in the Local Area Network.

Dial up

Dialup access is a way of connecting a computer to the Internet using a modem and the telephone line. It is rather slow and blocks the telephone line.

DNS

Domain Name System.  Internet service that maps Internet domains into corresponding IP addresses.  DNS database is distributed and replicated among many DNS servers, so when you change your domain's IP address, the changes take a while to propagate.

Domain name

Domain name is an easy-to-remember address that can be translated by DNS into server's IP address.  Domain names are hierarchical.  Domain's suffix indicates which TLD (top level domain) it belongs to, for example .com, .gov, .org, .net, or .jp.  Recently ICANN (Internet Corporation for Assigned Names and Numbers) added several new TLDs, like .biz, .pro., and .museum.

DSL

Digital Subscriber Line. A better way of connecting a computer to the Internet using the telephone line. It's faster than the dialup and doesn't block the telephone line. However, it is more expensive because the special equipment is required.