DB9, DB15, DB15HD, DB25, DB37, and DB50 are the common names for D-shaped connectors used to data communications. The number indicates the number of possible pins in sockets in the connector.

Data transfer rate is the speed with which data can be transmitted from one device to another. Data rates are often measured in mbps.

DTE stands for Data Terminal Equipment, and DCE stands for Data Communications Equipment. These terms are used to indicate the pin-out for the connectors on a device and the direction of the signals on the pins. Your computer is a DTE device, while most other devices such as modem and other serial devices are usually DCE devices

Decryption is the process of converting encrypted data back into its original form, so it can be understood

DHCP (Dynamic Host Configuration Protocol) assigns IP addresses dynamically from an IP address pool, which is managed by the network administrator. Once the user disconnects from the Internet, their dynamic IP address goes back into the IP address pool so it can be assigned to another user. Even if the user reconnects immediately, odds are they will not be assigned the same IP address from the pool.

In the dynamic IP mode, users don't have to specify all the parameters manually such as IP addresses, the network subnet mask, the gateway computer and the domain name server computers. This means computer receives a different IP address each time it boots up. For more information, please refer to this page http://www.networksorcery.com/enp/protocol/dhcp.htm

An attachment to an electronic message used for security purposes. The most common use of a digital certificate is to verify that a user sending a message is who he or she claims to be, and to provide the receiver with the means to encode a reply.

A digital certificate is an electronic "credit card" that establishes your credentials when doing business or other transactions on the Web

The most widely used standard for digital certificates is X.509.

DNS (Domain Name System or Service) is an Internet service that translates domain names into IP addresses. Because domain names are alphabetic, they're easier to remember. The Internet however, is really based on IP addresses. Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address. For example, the domain name www.sena.com might translate to 198.105.232.4. For more information, please refer to this page http://www.networksorcery.com/enp/protocol/dns.htm

A domain name locates an organization or other entity on the Internet. For example, the domain name

www.sena.com

locates an Internet address for "sena.com" at Internet point xxx.xxx.xxx.xxx and a particular host server named "www". The "com" part of the domain name reflects the purpose of the organization or entity (in this example, "commercial") and is called the top-level domain name.

The domain name system (DNS) is the way that Internet domain names are located and translated into Internet Protocol addresses. A domain name is a meaningful and easy-to-remember "handle" for an Internet address.

DSL (Digital Subscriber Line) is a technology for bringing high-bandwidth information to homes and small businesses over ordinary copper telephone lines. xDSL refers to different variations of DSL, such as ADSL, HDSL, and RADSL

Dynamic DNS is the ability to automatically update a DNS server when an IP address is automatically assigned (typically from DHCP) to a network device. A dynamic DNS (domain name system) service is a company that charges a small fee to allow a user connecting to the Internet with a dynamic IP address.