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Dark fibre
Fibre optic cable without the necessary equipment to transmit a telecommunication signal over the fibre. A telecommunication network operator can sell the right to use their dark fibre to other carriers or directly to end users, who have the obligation of supplying the necessary electronics to transmit on the fibre.
Data Centre
Purpose built facility providing a secure, resilient environment for server and firewall hosting.
Dedicated server
A server which is used solely for one company's purpose, it is not shared with any other party. This can be located at the company's own premises or located/managed by Star from our Data Centre.
See also Virtual server; Data Centre
DES
(Data Encryption Standard) - Is a widely used method of data encryption that uses a 40-bit and 56-bit key to encrypt and decrypt data. DES and Triple-DES are used as encryption algorithms by S/MIME.
See also S/MIME
DHCP
(Dynamic Host Configuration Protocol) – This is a protocol that lets network administrators centrally manage and automate the assignment of IP Addresses on the corporate network. When a company sets up its computer users with a connection to the Internet , an IP address must be assigned to each machine. Without DHCP , the IP address must be entered manually at each computer . DHCP lets a network administrator supervise and distribute IP addresses from a central point and automatically sends a new IP address when a computer is plugged into a different place in the network. DHCP uses the concept of a ‘lease’ or amount of time that a given IP address will be valid for a computer. Using very short leases, DHCP can dynamically reconfigure networks in which there are more computers than there are available IP addresses
See also IP Address
See Configuration Scenarios for full details
Dial-up
Term used to describe an Internet connection that is not 'always-on', you have to 'dial-up' to access the Internet. You are charged on a usage basis rather than a fixed fee, as with leased line and broadband connections. Dial-up connections use either your normal telephone line or an ISDN line.
See also ISDN; broadband
Directory
A directory is a system that your computer uses to organise files on the basis of specific information. Directories can be organised hierarchically so that files appear in a number of different ways, such as the order in which they were created, alphabetically by name or by type, and other ways.
DNS
An acronym for Domain Name Server, DNS is used to map names to IP addresses and vice versa. Domain Name Servers maintain central lists of domain name/IP addresses and map the domain names in your Internet requests to other servers on the Internet until the specified web site is found.
see also Domain name; IP Address
See Domain Name Service for full details
Domain Name
The domain name is the unique name that identifies an Internet site. The Internet is made up of hundreds of thousands of computers and networks, all with their own domain name or unique address. Domain names always have two or more parts separated by dots. A given server may have more than one domain name, but a given domain name points to only one server.
See also DNS
DSL
An acronym for Digital Subscriber Line, DSL is a technology that dramatically increases the digital capacity of ordinary telephone lines (the local loops) into the home or office. DSL speeds are tied to the distance between the customer and the telco central office. DSL is geared to two types of usage. Asymmetric DSL (ADSL) is for Internet access, where fast downstream is required, but slow upstream is acceptable. Symmetric DSL (SDSL, HDSL, etc.) is designed for short haul connections that require high speed in both directions.
Unlike ISDN, which is also digital but travels through the switched telephone network, DSL provides "always-on" operation.
See also ADSL; SDSL, ISDN
DWDM
An acronym for Dense Wave Division Multiplexing, DWDM is the technology by which the frequencies of light carried on a single optical fibre are subdivided into discrete wavelengths allowing for the greater transmission of data.
Dynamic IP
The term used to describe how IP address is dynamically assigned to computers as and when needed. Unlike Static IP addresses, the IP address is temporary e.g. when you connect to your ISP using a dial-up connection , your PC or router will be dynamically assigned an IP address whilst you are on-line.
See also IP Address
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