D
D ChannelA channel that carries WAN synchronization and signaling information on a T1 PRI or EI PRI line.
D4-frame
A T1 line uses the D4 format, also known as the superframe format, to frame data at the physical layer. The D4 format consists of 12 consecutive frames, each one separated by framing bits.
DBA
Dynamic Bandwidth Allocation. Adding or subtracting bandwidth from a switched connection in real time without terminating the link. MPP and AIM support Dynamic Bandwidth Allocation based upon a set of parameters you specify.
DBM Database
A RADIUS users file in a UNIX database format. Compare with flat ASCII users file.
DBMS
Database management system. A collection of programs that enables you to store, modify, and extract information - organized in fields, records, and files - from a database.
DBS
Direct Broadcast Satellite.
DC
Direct Current
DCE
Data communications equipment or data circuit-terminating equipment. Devices and connections of a network that make up the network end of the interface between the network and the user. A modem is an example of a DCE.
DCE (Data Circuit-Terminating Equipment)
As defined in the RS-232 specification, equipment to which DTE (Data Terminal Equipment) is connected, often to enable access to network facilities. A DCE converts the format of the data coming from the DTE into a signal suitable to the communications channel. DCE often refers to equipment such as network access equipment, and DTE refers to application equipment, such as a videoconference terminal.
DDE
Dynamic data exchange. A form of communication that uses shared memory to exchange data between applications.
DDP
Datagram Delivery Protocol
DE
Discard Eligibility
DGP
Dissimilar Gateway Protocol
DHCP
Dynamic Host Configuration. DHCPis a standards-based protocol for dynamically allocating and managing IP addresses. DHCP runs between individual computers and a DHCP server to allocate and assign IP addresses to the computers as well as limit the time for which the computer can use the address. When the time expires on the use of the IP address, the computer must contact the DHCP server again to obtain an address.
DHCP Spoofing
There are some cases where the DHCP server is on a remote network, and an IP address is required to access the network, but since the DHCP server supplies the IP address, the requester is at an impasse. To supply access to the network, when the Pipeline receives a DHCP Discover packet (a request for an IP address from a PC on the network), it responds with a DHCP Offer packet containing the configured (spoofed) IP address and a renewal time, which is set to a few seconds. The requester then has access to the DHCP server and gets a real IP address. (Other variations exist in environments where the APP server utility is running.)
DLCI
Data link connection identifier. A unique number that represents a particular permanent virtual circuit on a particular physical segment of the Frame Relay network.
DLCI (Data Link Connection Indicator)
In a Frame Relay network, DLCIs uniquely identify each virtual circuit. In most circumstances, DLCIs have strictly local significance at each Frame Relay interface.
DLL
Dynamic link library. A file containing executable routines-generally performing a specific function or set of functions-that is stored separately, loaded into memory only when required, and unloaded when space is needed for other applications. A DLL conserves memory, can be shared by other programs, and can be modified without changes to the calling program or other DLLs.
DLO
Data Line Occupied
DMA
Direct memory access. Transfer of data from a peripheral device, such as a hard disk drive, into a computer memory without mediation by a microprocessor.
DNS
Domain Name System. A TCP/IP service that enables you to specify a symbolic name instead of an IP address. A symbolic name consists of a user name and a domain name in the format user name@domain name. The user name corresponds to the host number in the IP address. The domain name corresponds to the network number in the IP address. A symbolic name might be steve@crocker.com or joanne@cal.edu. The domain identifier is the last part of the domain name, and identifies the type of organization to which the host belongs.
DOSBS
Data Over Subscriber Bearer Service. This is the same as 3.1 Khz audio bearer service.
DRAM
Dynamic random access memory. A type of semiconductor random access memory that stores information in integrated circuits.
DS0
A 64 kbit/s unit of transmission bandwidth. A worldwide standard speed for digitizing one voice conversation, and more recently, for data transmission. Twenty-four DS0s (24x64 kbit/s) equal one DS1.
DS1
A 1.544 Mbit/s unit of transmission bandwidth in North America, and a 2.048 Mbit/s unit of transmission elsewhere. A telephony term describing a 1.544 or 2.048 Mbit/s digital signal carried on a T1 facility.
DS1 Channel
For a T1, a 1.544 Mbps unit of transmission bandwidth in North America, and a 2.048 Mbps unit of transmission elsewhere. A telephony term describing a 1.544 or 2.048 Mbps digital signal carried on a T1 facility.
DS2 Channel
For a T1 line, a 6.312-Mbps channel that consists of four DS1 channels; for an E1 line, an 8.45-Mbps channel that consists of four DS1 channels.
DS3 Channel
A 44.736-Mbps line consisting of seven DS2 channels. A DS3 line is also called a T3 line.
DSL
Digital subscriber line. A modem technology for transmitting information at high speeds on existing copper phone lines to homes and businesses. DSL operates over existing copper telephone lines and require runs of usually less than 20,000 feet to a central telephone office. Types of DSL include asymmetric DSL (ADSL), symmetric DSL (SDSL), high-data-rate DSL (HDSL).
DSL MAX
A digital subscriber line (DSL) access concentrator that provides high-speed secure access over existing telephone wires within buildings or local loops. The DSL MAX is ideally suited for multi-dwelling units (MDUs), small central offices, hotels, and campus/ enterprise applications.
DSLPipe
A Lucent product that enables you to take advantage of high-speed SDSL services. This powerful router lets you access multiple destinations simultaneously in order to download high-resolution graphics, access multimedia applications, or transmit large files from a corporate intranet.
DSR
Data Set Ready
DSU
A digital service unit, tasked to convert terminal interfaces such as RS-2323 connections to DSX-1 interfaces. Increasingly, the functions of these DSUs are incorporated into sophisticated remote access devices located at the central site.
DTE
Data Terminal Equipment. As defined in the RS-232 specification, equipment to which DCE (Data Communications Equipment) is connected, such as personal computers or data terminals. DTE refers to application equipment, such as a videoconference terminal or LAN bridge or router, while DCE refers to equipment such as network access equipment.
DTH
Direct to Home. Predecessor to DBS (direct broadcast satellite)
DTMF
Dual-Tone Multifrequency
DTR
Data Transmit Ready
DWDM
Dense wavelength division multiplexing
Daemon
A type of program that, once activated, carries out a specific task without user intervention. A daemon typically handles a task that runs repeatedly, such as printing, mail, and communications services.
Data Base Connector
A DB connector is a cable connector for parallel or serial ports. The number following DB indicates the number of pins on the connector. For example, a DB-25 has 25 pins.
Data Bits
In asynchronous transmission, the bits which contain the data being sent. Data bits are sometimes referred to as a payload.
Data Carrier Detect (DCD)
DCD is a hardware signal defined by the RS-232C standard. It indicates that the device is online and ready to receive a transmission.
Data Communication Equipment (DCE)
Any device that connects a DTE to a communication line. Modems and channel service/data service units (CSU/DSU) are two types of DCE.
Data Communications
The transfer of data between points.
Data Communications Equipment (DCE)
In the RS-232-C standard specification, there are DCE devices (modems or printers) and DTE (data terminal equipment) devices (personal computers or data terminals). The main difference between a DCE and DTE is the wiring of pins two and three. Check with the wiring diagram; but typically with an RS-232-C connection, the modem is usually regarded as DCE, while the user device (terminal or computer) is DTE.
Data Compression
A method for current modem standards and protocols to attain higher rates of speed. Compression algorithms, such as those in the V.42bis standard, take advantage or redundancies in data files by substituting a few characters for many. Compression is especially effective with text files and certain graphic-file formats, and has become an important topic for network administrators as multimedia, video, document imaging, and other technologies emerge.
Data Encryption
Encypting data is accomplished by applying a special scrambling code that makes the data unreadable to anyone who does not have a decryption key. Authorized personnel with access to this key can unscramble it. Data encryption is a useful tool against network snoopers.
Data Exchange Interface (DXI)
Described in RFC 1483, DXI defines how a network device can convert data for transmission between different network services.
Data Filters
A data filter is a filter that applies to the actual data stream. It can be set to drop packets addressed to particular hosts or to prevent packets from going across the WAN.
Data Line Interface
The point at which a data line is connected to a telephone system.
Data Link Connection Identifier (DLCI )
The frame relay virtual circuit number corresponding to a particular destination which is part of the frame relay header and is usually ten bits long.
Data Link Layer Protocols
The second layer of the Open Systems Interconnection (OSI) reference model created by the International Standards Organization (ISO). The data link layer assembles messages and coordinates their flow. The term can also be used to refer to a connection between two computers over a telephone.
Data Network
A network that connects computer systems for transmitting data.
Data Over Voice
Sending digital data over telephone trunks conditioned for voice. Data over voice is sometimes used to mean sending data using voice bearer service or 3.1 Khz audio bearer service.
Data Service
A service provided over a WAN line and characterized by the unit measure of its bandwidth. A data service can transmit either data or digitized voice.
Data Svc
A settable parameter in telco options in the menu interface under the connection profile.
Data Terminal Equipment (DTE)
Any device that sends information to or receives information from any other device on the network. Personal computers are an example of DTE. So are both terminals and hosts in terminal-to-host networks.
Data Transmit Ready
DTR is a signal indicating that a device is ready to transmit and receive data.
Data-transfer Mode
The speed at which data is transferred, usually measured in megabits per second (Mbps).
Database
A large collection of data organized for rapid search and retrieval, relatively simple management, and ease of updating. Traditional databases are organized by fields, records, and files. A database management system (DBMS) is required to access information from a database.
Datagram
A message unit that contains a source address, destination address, and data. A datagram is routed through a packet-switched network.
Dedicated Line
A communications circuit used for one specific purpose, and not shared between users.
Dedicated Server
A network device that functions only as a server, performing specific network tasks.
Default
A factory-set hardware or software setting or configuration. It is the preset value that the program or equipment comes with.
Default Gateway
When setting up the PC to operate with a Pipeline, the gateway setting (in the Network settings) must be set to the IP address of the Pipeline. Using the IP address of the Pipeline as the gateway, lets your computer know that you will use the Pipeline to access remote networks.
Defense Advanced Research Projects Agency (DARPA)
Formerly called ARPA. The government agency that funded research and experimentation with ARPANET and later the Internet. The group within DARPA responsible for the ARPANET is ISTO (Information Systems Techniques Office), formerly IPTO (Information Processing Techniques Office).
Defense Communication Agency (DCA)
Responsible for installation of Defense Data Network.
Define Path
A function that allows you to define a manual path for the permanent virtual circuit (PVC), bypassing the Open Shortest Path First (OSPF) algorithm for PVC routing decisions.
Delay
Wait time between two events. For example, the time between when a signal is sent and when it is received.
Demilitarized Zone (DMZ)
A special LAN that is on the public network side of the firewall. DMZs allow a single WAN router or access switch to support both private (VPN) and public access to resources. Normally, publicly accessible Web and other servers are placed in the DMZ.
Dense Wavelength Division Multiplexing
Using optical multiplexers and optical amplifiers, DWDM combines multiple optical signals so they can be amplified as a group and transported over a single fiber to increase capacity.
Dense Wavelength Division Multiplexing (DWDM)
Using optical multiplexers and optical amplifiers, DWDM combines multiple optical signals so they can be amplified as a group and transported over a single fiber to increase capacity.
DeskDial Client
Lucent client software for network modem pool access.
Destination
The final autonomous system whose IP address prefixes are reported in the network layer reachability information field of an update message. A destination and its path comprise a Border Gateway Protocol route.
Destination Address
In a frame, packet, or message sent over a bridged or routed connection, the IP, IPX, AppleTalk, or hardware address of the intended recipient of the transmission.
Destination Node
System nodes that receive messages over the control packet network from the transmitting node.
Destination Port
The port to use to communicate with the destination machine, such as a User Datagram Protocol (UDP) Port on an authentication server, or a Simple Mail Transfer Protocol (SMTP) Port on a mail server.
Detail File
A file containing RADIUS accounting records.
Dial #, Phone #
The preferred term is dial #.
Dial Query
Dial query is a parameter of a connection profile that tells the Pipeline to initiate the connection when a local NetWare client queries a remote server and the Pipeline routing table is empty. (A routing table is a list of destinations known to the Pipeline.)
Dial String
The sequence of characters sent to a device, such as a modem, that can dial a telephone number.
Dial-in Modem Access
The ability of a remote worker using a modem with a PC or other computer device to dial into a remote access server (RAS) at the corporate office, a central-site location, or a service provider’s point-of-presence (POP).
Dial-in User
A remote user or device that calls the Lucent unit over a switched circuit and requests a connection.
Dial-out Modem Access
The ability of a user at a workstation on a corporate LAN to dial out through a shared modem to a service provider’s point-of-presence (POP) or a branch-office location.
Dial-out Timer
A timer that specifies the maximum number of seconds the system waits for a call setup complete from the remote side when dialing out.
Dial-up Line
A connection or circuit between two sites through a switched telephone network. A dial-up is most commonly associated with a voice telephone call between two locations. For modem access, a dial-up line forms a link between two distant pieces of equipment, such as computers or LANs. Not restricted to landline connections, a dial-up connection can also be established through a circuit-switched cellular network or a combination of landline and cellular or wireless
Digital
A type of signal that represents information as a discrete voltage, or intensity level. Digital+D16 transmission is typically used for modern telephony and data networking.
Digital Access And Cross-connect System (DACC, DACS)
A digital switching device for routing and switching T1 lines.
Digital Compression
The technology that encodes digital information to take up less storage space or to require less bandwidth for efficient transmission.
Digital Compression Program Delivery System
A system to move and manage video programming over satellite and cable distribution facilities. It includes encoding and decoding equipment and software, as well as multiplexing and transmission systems for efficient program delivery.
Digital Cross Connect
An electronic switching system, found in telephone central offices, that switches groups of signals from one route to another, without the need to demultiplex them. An optical cross connect is an optical switch that routes wavelength channels from one fiber route to another without first converting them into electricity and back.
Digital Data
Data that can have only a limited number of separate values. The time of day represented by a digital clock, or the temperature represented by a digital thermometer are examples of digital data; the digital values do not change continuously, but remain at one discrete value and then change to another, discrete value.
Digital Data Service (DDS)
In telecommunications, a private line channel at 56 or 64 Kbps.
Digital Dial-Up Bandwidth
Communications channels created by signaling to the network, from the caller's site, the intended destination of the connection. These channels may be terminated when the caller or called party chooses. The user pays for the bandwidth only when it is used. Digital Dial-Up Bandwidth operates in a fashion similar to the dialed voice telephone network, but the resultant connections are digital and of specified bandwidths.
Digital Enhanced Cordless Telecommunications (DECT)
A wireless communications standard used in Europe, the Mid-East and Africa.
Digital Loop Carrier (DLC)
DLC is equipment that concentrates analog local loop lines, digitizing and multiplexing calls for transmission to the central office.
Digital Modem
A system component which allows communication over digital access facilities with a remotely located system connected to the public network over analog facilities. Converts incoming digital data stream containing PCM-encoded modem waveform into actual data contained in waveform at data rate transmitted by far-end modem; performs inverse function for outgoing data stream.
Digital Multiplexer System (DMS)
Digital multiplexer system.
Digital Private Network Signaling System (DPNSS)
DPNSS is a standard that defines how different private branch exchange (PBX) systems can interoperate to produce a single virtual PBS.
Digital Signal
A type of signal that encodes data transmitted over a wire using a limited number of discrete values. The value of the data encoded in a digital signal depends upon the state of the signal during a particular time period. Therefore, the sender and the receiver must synchronize their clocks. Each clock runs at a baud rate, the number of times per second the state of the signal is read or set. Several clocking schemes are available, and digital signals often include clock timing cues.
Digital Signal Level (DSO)
In telecommunications, hierarchical arrangement of digital signals beginning at DS0 (64 Kbps) up to DS3 (45 Mbps).
Digital Signal Processor
A DSP analyzes and processes analog signals, converting them to a digital format.
Digital Signal Processor (DSP)
Invented at Bell Labs in 1980, a semiconductor chip that runs at turbo speed to convert analog signals, such as voice and video, into digital form. It then performs mathematical computations on the signal to compress it for transmission. DSPs made possible modern communications devices like cellular phones, pagers, modems, and digital answering machines.
Digital Spread Spectrum Frequency Hopping
Radio technology that operates by expanding a single message over a broad frequency range rather than a single, narrow band.
Digital Subscriber Line (DSL)
A modem technology that increases the digital speed of ordinary telephone lines by a substantial factor over common V.34 (33.6 Kbps) or V.90 (56 Kbps) modems. DSL technologies are either asymmetric or symmetric. Asymmetric provides faster downstream speeds, which is suited for Internet usage and video on demand. Symmetric provides the same rate coming and going.
Digital Technology
Technology that converts a message to a series of computer codes. Each bit of code has a possible value of only "1" or "0." In telephony, this technique enhances security, delivers virtually interference-free conversations, and makes possible advanced services.
Digital-to-analog Conversion
D-A conversion is a process in which a digital signal is modified into an analog signal. D-A conversion takes place, for example, when digital data reaches an analog modem.
Diode
An electronic device that controls the flow of electrons. A diode lets current flow in only one direction.
Diplexer
A device that allows the feeding of signals from two transmitters to a single antenna at the same time without interference.
Direct Line Trunk
A logical configuration that allows a direct trunk connection to another Lucent switch on a frame relay network. The trunk connection carries traffic destined for other switches in the network using Lucent’s trunk protocols. This configuration takes advantage of such value-added features as manually defined paths, and are rate-monitoring designators for frames.
Direct Modulation
The process in which a RF or digital signal is a applied directly to a laser for transmission.
Direct Route
A route that can reach a destination without going through any intervening routers.
Direct broadcast satellite
System of delivering satellite television signals direct to the home.
Directory Enabled Networks (DEN)
The management of a network from a central depository of policy-based information about users, applications and network resources. DEN is an emerging standard that is expected to supplant other systems now used for managing VPN membership, such as RADIUS.
Disaster Recovery
The use of alternative network circuits to reestablish communications channels in the event that the primary channels are voice. Data over voice is sometimes used to mean sending data using voice bearer service or 3.1 Khz audio bearer service.
Disconnect-request Packet
A message from a client of the Lucent unit, asking the Lucent unit to disconnect the session.
Discrete Device
An electronic device that contains only one active element, such as a transistor or diode. Compare to integrated circuits, the latest of which contain millions of transistors and other devices.
Discrete MultiTone (DMT)
A modulation method that divides the frequency range into 256 subfrequencies, from 64 KHz to 1.1 Mhz. Each subfrequency is an independent channel with its own signals.
Disk Capture Feature
A feature that allows your terminal emulator to capture to disk the ASCII characters it receives as its serial port.
Dispersion
In fiber optics, dispersion indicate the pulse spreading limitations of a fiber.
Distortion
The variance between two measures of a signal; for example, a signal as it is transmitted versus the signal as it is received.
Distributed Computing Environment
An arrangement of servers and clients in which portions of the applications and the data reside on the various elements.
Distributed Database
A database that can be dispersed or replicated among different points in a network. See also database.
Distributed-Queue Dual Bus (DQDB)
Also known as IEEE 802.6, this protocol was used as the standard medium access control (MAC) protocol in local area networks. DQDB was modeled after the QPSX (Queued Packet and Synchronous Exchange).
Domain Identifier
The portion of a domain name that appears last and specifies the type of organization to which the host belongs. The Internet's Network Information Center (NIC) provides these domain identifiers:
Domain Name
The portion of a symbolic name that corresponds to the network number in the IP address. In the symbolic name steve@crocker.com, the domain name is crocker.com.
Doping
Also called ion implantation. The introduction of a selected chemical impurity, such as phosphorous or boron, into the crystal structure of a semiconductor to change its electrical properties. For example, adding phosphorous transforms the crystal into a negative conductor of electricity.
Downstream Path
The path a call takes from a carrier’s central office to the end user’s home.
Drop and Insert
A process of adding data (insert) to a T1 data stream, or terminating data (drop) from a T1 data stream to other devices connected to the drop and insert equipment.
Dual 56
Two switched 56 calls made between videoconferencing equipment to allow data transfer at 112 kbit/s. The videoconferencing equipment performs a two-channel inverse-multiplexing procedure to assure channel alignment.
Dual Homing
A network topology in which a device is connected to the network through two independent access points, or points of attachment.
Dual IP
A method of assigning a second IP address to the Ethernet interface in order to give the Lucent unit a logical interface on two networks or subnets on the same backbone.
Dual-Port Call
A call in which the serial host (such as a video codec) performs inverse multiplexing on two channels so that the call can achieve twice the bandwidth of a single channel. The serial host provides two ports, one for each channel. Two serial host ports on the MAX connect a dual-port call to the serial host; these ports are the primary port and the secondary port. Because the MAX places the two calls in tandem and clears the calls in tandem, it considers them a single call.
Dual-Tone Multifrequency
DTMF is a technology enabling a touch-tone telephone to create 16 tones by means of 8 frequencies.
Dynamic Bandwidth Overflow
This is the mode enabled to supplement bandwidth during periods of peak demands. Through the mechanism of inverse multiplexing, additional bandwidth is dialed up when traffic reaches a preassigned level. E1
Dynamic Data Exchange (DDE)
The ability to have two programs share data, such as financial figures stored in a spreadsheet linked to a word processor report. When the user makes changes to data in one program, these changes are automatically reflected in the other program.
Dynamic IP
The process of assigning an IP address to a dial-in caller from an IP address pool.
Dynamic Random Access Memory (DRAM)
The readable/writable memory used to store data in PCs. DRAM stores each bit of information in a "cell" composed of a capacitor and a transistor. DRAM must be continually refreshed to retain its data. In contrast, static RAM or SRAM, requires no refresh and delivers better performance, but it is more expensive to manufacture.
Dynamic Route
A path to another network that the router learns by means of dynamic updates from other routers, rather than by means of a static specification in a configured profile. Routers that use Routing Information Protocol (RIP) broadcast their entire routing tables every 30 seconds, updating other routers about which routes are usable. Hosts that run Internet Control Message Protocol (ICMP) can also send ICMP redirects to offer a better path to a destination network. Open Shortest Path First (OSPF) routers propagate link-state changes as they occur in order to update their routing tables.
Dynamic Routing
A routing technique that enables a message’s route to change as the message proceeds along the network.
dB
deciBel, defined as 10 multiplied by the logarithm of the ratio of two power levels.
.jpg)