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Jargon Buster
The du Pré Jargon Buster found the following for - DNos A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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Term
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Explanation
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| D Channel | The ISDN channel that carries the signalling information between users | |
| Dark | Owned. Eg, ‘Dark fibre’ means fibre which is owned. See ‘Light’ | |
| DARPA | Defence Advanced Research Projects Agency. See TCP/IP | |
| DASS2 | Digital Access Signalling System number 2. BT’s proprietary signalling system for the ISDN which has not been adopted by ETSI as the European standard. Based on BT’s BTNR 190. New supply was terminated in 2002 | |
| DAT | Digital Audio Tape. Often used as a medium for data back-up | |
| Data Driven Attack | A form of intrusion in which the attack is encoded in seemingly innocuous data, and it is subsequently executed by a user or other software to actually implement the attack. | |
| Data Link | A segment of cabling, either hard wired or soft wired. E.g., a hard wired link could be one of the cables from the patch panel to the socket, and a soft wired link could be a patch lead, or a fly lead – see Topology | |
| DateLink | A BT term. Associted with BT's Advanced Features. Many businesses will wish to arrange for calls to be dealt with differently (in terms of where and how calls are answered) at weekends as compared to weekdays; these two set treatments constitute a straightforward, regular weekly pattern. However, a business may require Bank Holidays to be dealt with in a different way again; furthermore, it may require each individual Bank Holiday to be dealt with in a different manner. | |
| Daughter Extension | A facility only available on some telephone systems. A Daughter Extension is the term given to an extension which has been cabled to another extension instead of the CCU of a telephone system. Hence, both the daughter and parent extensions are connected to the CCU using the same cable. The parent always has to be a keyphone. Both extensions can be used simultaneously, each with its own extension number. Depending on the telephone system, the daughter extension may either be a POT or a keyphone. Connection of the daughter is either direct to the parent, or to a small optional card inserted into it | |
| DayLink | A BT term. Associted with BT's Advanced Features. Different arrangements made for different days of the week - e.g., weekends productivity enhanced by tailoring resources to meet different calling patterns | |
| dB | see Decibel | |
| DB-25 | The colloquial name given to the 25 pin connector | |
| DC | An electrical term, referring to Direct Current. The opposite of AC | |
| DC10 | The signalling that preceded DC5. Almost extinct, but sometimes found in use with very old BT telephone systems | |
| DC5 | The type of signalling used on an analogue ‘speech line’ which joins two telephone systems, or links a telephone system to a multiplexor, for example. Requires either a 4 or 6-wire speech line but can only cope with distances of up to 120 metres. The cost of DC5 is less than AC15A | |
| DCE | A Frame Relay term. Data Circuit Terminating Equipment. The switching equipment in the network to which DTEs attach. A network node or equipment at which a network circuit terminates, such as a modem or bridge | |
| DDE | Dynamic Data Exchange is software which provides a link between documents created in different Windows based application programs, eg, MS Word and MS Excel. The advantage of using DDE is that when information is updated in the linked document using its native application, it is also updated in the main document of the primary application | |
| DDI | Direct Dialling Inwards. A BT Digital Select Service available from some other PTOs as well. Where a specific telephone number can be dialled to target an extension on a telephone system | |
| DE | A Frame Relay term. Discard Eligibility. User-set bit indicating that a frame may be discarded in preference to other frames if congestion is encountered, to maintain the committed quality of service within the network. Frames with the DE bit set tend to be considered Be excess data by frame relay networks | |
| Decibel | The smallest increment in sound loudness detectable by the human ear | |
| DECT | Digital European Cordless Telephony. Created in 1988 by ETSI. Able to transmit data at 552Kbit/s and using 1880 – 1900MHz with 20MHz bandwidth, 1.728MHz carrier Due to ETSI’s radio transmission requirements for DECT, handsets will ring for up to 2 additional rings if an incoming call is hung up ended before being answered | |
| Dedicated Server | A computer on a network which is assigned a single task such as a print server or file server | |
| DEL | Direct Exchange Line. A PSTN exchange line provided independently from any other, which terminates on its own dedicated Master Socket | |
| Denial of Service Attack | A user or program takes up all the system resources by launching a multitude of requests, leaving no resources and thereby "denying" service to other users. Typically, denial-of-service attacks are aimed at bandwidth control. | |
| Dense Wave Division Multiplexing | A technology which provides immense throughput, using more than 8 different light colours, each of which is used as a data stream. The theoretical maximum is 32 x 2.5Gbit/s | |
| DHCP | Dynamic Host Configuration Protocol. An extension of BOOTP, which can provide just about any information required for network configuration. Although not widely prevalent, DHCP could eventually be a service found on all corporate networks, and also provided by ISPs in preference to IPCP | |
| Dial Pulse | The original method of automatic mechanical dialling, originally used with the Strowger exchange, and still in use today. Each digit would be composed of the same number of on/off pulses as the number being dialled, transmitted at a rate of 10 pulses per second. Hence, each digit would take approximately one second to transmit. Allowed the sending of digits 1 to 0 (ten) | |
| Dial Up | A connection to an Internet Services Provider (ISP) over the PSTN or ISDN | |
| Dialplus | A BT service, which in some geographical areas, allows V.90 compatible modems to access the service at a maximum speed of 28.8k (V.34 protocol). The service runs with packet size of 256k | |
| DID | Direct Inward Dialling. Where a PSTN line is connected to a telephone system, and programmed to ring a specific extension | |
| Digital Certificate | A Digital Certificate service is for use over open networks such as the Internet, Intranets and Extranets. A Digital Certificate acts as a digital ID for users required to give some proof of their identify online and offers senders and recipients of e-mail the ability to encrypt and authenticate messages. It also enables Web sites to confirm the customer's identity and status - essential for customer trust | |
| Digital Select Services | see BT Digital Select Services | |
| Digital Signal | A series of ‘on/off’ signals. Also known as ‘one/zero’, or ‘yes/no signals | |
| Digital Signature Standard | see DSS. | |
| Digital Subscriber Line | see ADSL | |
| DIMM | Dual In-Line Memory Module. Similar to SIMM, but less preferred | |
| Direct Connection | Refers to products which are able to be connected to a PTO’s network either by plugging into a telephone socket, or by being hard-wired – physically cabled to the network | |
| DISA | Direct Inward Station Access. A facility offered by some telephone systems where the system answers the incoming call, returns internal dial tone, whereupon the caller can dial the required extension | |
| Disconnect Clear time | A ‘slang’ term for Calling Party Clear (CPC) time | |
| Disk Mirroring | A security feature which protects against HD failure by copying data from one disk to another. The latter operates automatically should the first fail | |
| Display Adaptor | Also known as a video controller or graphics adaptor. Interprets date to display it on a VDU | |
| DistributionLink | A BT term. Associted with BT's Advanced Features. Reduces the chances of calls not being answered callers receive consistent response levels answering resources are maximised ideal for businesses with a number of answering centres. | |
| Diversity | A BT network term. Used where BT provides a client with more than one route through the network, although the user connection will be provided from one exchange | |
| Divert Busy/No Reply | A BT term. Associted with BT's Advanced Features. Reduces the chances of calls not being answered. Useful for small businesses, tele-workers. | |
| DivertLink | A BT term. Associted with BT's Advanced Features. ideal for short-term ad hoc arrangements no need to resort to a second number for callers to make contact reduces cost changes can normally be put into effect within 30 minutes useful for small businesses. | |
| DLCI | A Frame Relay term. Data Link Connection Identifier. Unique number assigned to a PVC end point that has local significance only. Identifies a particular PVC endpoint within a user’s physical access channel in a frame relay | |
| DMI | Desktop Management Interface. An open industry standard for managing PCs and peripherals more efficiently | |
| DMZ | De Militarised Zone. A network added between a protected network and an external network in order to provide an additional layer of security. Sometimes called a Perimeter Network. | |
| DND | Do Not Disturb – a telephony term | |
| DNS | An Internet term. Domain Name System. The system that locates the numerical IP address corresponding to a host | |
| DNS Spoofing | Breaching the trust relationship by assuming the DNS name of another system. This is usually accomplished by either corrupting the name service cache of a victim system or by compromising a domain name server for a valid domain. | |
| Domain | Refers to a functional group of users on a network, such as the marketing or accountancy domains | |
| Domain Name | The name used when locating an IP address, such as dupre.co.uk | |
| Domain Name Server | A repository of addressing information for specific Internet hosts. Name servers use the domain name system to map IP addresses to Internet hosts. | |
| DOS | The widely used abbreviation for Data Operating System, which comprises a program or suite of programs that manages a disk-based computer system. It schedules and supervises work, and allocates computer resources and the operation of peripherals. There are a number of versions of DOS from different vendors, some of which have several updated versions. The most common forms for PCs are Microsoft's MS-DOS and IBM's PC-DOS. DOS 3.1 was the first version of MS-DOS and PC-DOS able to support LAN functions. One of its most important innovations was record and file locking which is now virtually standard on any multi-user system | |
| Download | The term used when copying a file from one media to another | |
| Downloadable | A "Downloadable" is a file that has been transmitted from one computer system to another, usually smaller computer system. From the Internet user's point-of-view, to download a file is to request it from another computer (or from a Web page on another computer) and to receive it. | |
| Downstream | A BT term. Indicates data flow to the End User | |
| DP | i) see Dial Pulse ii) Distribution Point. The point to which a multicore cable is terminated and split to smaller cables from onward distribution. DPs are usually boxes with Krone connections when associated with telephone systems |
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| dpi | Dots per inch (square inch). The density of printing | |
| D-PITS | A Panasonic telephony term. Digital Proprietary Integrated Telephone System. Typically applied to the integration capabilities of some Panasonic systems, such as the KX-TD 816 & 1232 telephone systems and KX-TVP100E & KX-TVP200E voice mail systems | |
| DPNSS | Digital Private Network Signalling System. The UK’s proprietary inter-PABX signalling system, developed in the early 1980s by a group of PABX manufacturers including BT. Presented using G.703 with a 64k timeslot per voice connection, and a separate 64k timeslot handling the signalling. Based on pre-ISDN technology. It is being replaced by ECMA’s Q.sig | |
| DRAM | Dynamic Random Access Memory. Less costly and slower than other forms of RAM | |
| Drop | An Internet access term. Drop time is the amount of time allowed before the connection is forcibly terminated | |
| Drop and Insert | A technique used with three or more TDM multiplexors whereby data is routed from one to another via an intermediate multiplexor | |
| Drop Cable | A cable that allows connection and access to the trunk cable in a network. It is also called AUI cable, and sometimes transceiver cable | |
| Drop Wire | see Catenary Wire. | |
| DSL | Digital Subscriber Line. See xDSL | |
| DSL Lite | Digital Subscriber Line – Lite. Same principles as ADSL, but at reduced speeds. Intended primarily for consumer high speed Internet access. Lower installation costs. 64k – 1.5 Mbit/s downstream & 32 – 512Mbit/s upstream. PSTN can be used and without a splitter. Max distance is 3 – 4.5km – see xDSL, ADSL, HDSL & VDSL | |
| DSLAM | Digital Subscriber Line Access Multiplexer. Allows a telephone line to make a faster connection to the Internet. It is a network device located near the customer's location, which connects multiple DSLs to a high speed Internet Backbone using multiplexing techniques | |
| DSS | i) Direct Station Selection. A proprietary device for use with a Keyphone to offer the equivalent of an Operator’s Console. Often called a DSS Console. ii) A Frame Relay term. Digital Subscriber Signalling. iii) Digital Signature Standard is a cryptographic standard promulgated by the National Institute of Standards and Technology (NIST) in 1994. It has been adopted as the federal standard for authenticating electronic documents, much as a written signature verifies the authenticity of a paper document. |
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| DSU | A BT term. Data Service Unit. The name given to the NTE for SMDS | |
| DSX | Dynamic Security Extension is a proprietary technology that is patented and works in the following way. The operating system has a system call (or vector) table that contains memory address pointers for each system call. These pointers point to a location in memory where the actual kernel code of the system calls resides. DSX stores the address pointers for the security sensitive system calls and then redirects these pointers to the corresponding SECURED system call code, which is located elsewhere in memory | |
| DTE | Date Terminal Equipment. CCITT terminology for the data terminal device such as a printer or PC | |
| DTI | Department of Trade and Industry | |
| DTMF | Dual Tone Multi-Frequency. For fast dialling on the PSTN. For any number dialled, two tones would be mixed and transmitted. These would be identified at the local exchange and de-coded into numbers. Introduced in the 1980s to replace Dial Pulse. Allowed the sending of digits 1 - 0 (ten) plus a star and a hash, making 12 numbers in all | |
| DTMF Receiver | A device to convert whatever method of dialling an analogue device uses into DTMF for dialling internally within a telephone system, or externally on an AC15 circuit or a PSTN exchange line. | |
| DTP | Desk Top Publishing. An advanced form of word processing | |
| du Pre Connect | see du Pré Connect. | |
| du Pré Connect | A pure VoIP system using non-contended broadband, removing the need for PSTN, ISDN, and SIP trunks, allowing total flexibility of location, disaster recovery, home working, and voice recording (as just some of the features) as well as no capital investment. | |
| Dual Access | A fax term. Allows reception of a fax whilst scanning another into memory to send | |
| Dual Homed Gateway | A system that has two or more network interfaces, each of which is connected to a different network. In firewall configurations, a Dual Homed Gateway usually acts to block or filter some or all of the traffic trying to pass between the networks. See Bastion Host. | |
| Dumb Terminal | A terminal which draws on the power of a central computer, usually a mini or main frame, having no processing power itself | |
| Duplex | Simultaneous, non-interfering transmission of two signals in opposite directions. Typically, where one can both speak and listen at exactly the same time on a telephone | |
| Duplexing | The same as mirroring, except the controller is included in the fault tolerance solution, eg, two controllers used | |
| DVD | Digital Versatile Disk. A new high capacity disk drive which many predict will supercede CD-ROM | |
| DXI | Data Exchange Interface | |
| Dynamic Security Extension | see DSX. |