Master Glossary

glossary glossary

User Manual: glossary

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Master Glossary

Symbols
µ-law

Mu-law. A mathematical function used to encode audio for transmission.

29 July 2005

GL-1

Master Glossary – Numbers

Numbers
1in8 Test

A test pattern consisting of a one (1) followed by seven zeros (on the network only).

10BaseT

A specification for baseband Ethernet running up to 10 Mbps on unshielded twisted-pair
wiring.

100BaseFX

A specification for baseband Ethernet running up to 100 Mbps on two strands of multimode
fiber optic cable.

100BaseT

A specification for baseband Ethernet running up to 100 Mbps on Category 5 or above
unshielded twisted-pair wiring.

100BaseTX

A specification for baseband Ethernet running up to 100 Mbps on two pairs of shielded or
unshielded twisted-pair wiring.

100BaseX

A general term comprising the 100BaseFX and 100BaseTX specifications.

1000BaseLX

A specification for baseband Ethernet running up to 1 Gbps on fiber optic cable using a long
wavelength laser.

1000BaseSX

A specification for baseband Ethernet running up to 1 Gbps on fiber optic cable using a
short wavelength laser.

1000BaseT

A specification for baseband Ethernet running up to 1 Gbps on Category 5 or above
shielded or unshielded twisted-pair wiring.

1000BaseX

A general term for high speed Ethernet based on IEEE 802.3z, including 1000BaseLX and
1000BaseSX.

16-CAP

Carrierless Amplitude/Phase Modulation with a 16-state constellation pattern.

2B1Q

Two Binary, one Quaternary. A line coding technique that compresses two binary bits of
data into one time state as a four-level code.

32767 Test

A pseudo-random bit sequence (PRBS) that is 32767 bits long (on the network only). This is
a PRBS 215-1 test.

4-wire private line

A dedicated data communications channel with separate transmit and receive pairs,
dedicated to one user only.

511

A random bit test 511 bytes in length.

511 bits

A random bit test 511 bytes in length.

511 Test

A pseudo-random bit sequence (PRBS) that is 511 bits long (on the data ports only). This is
a PRBS 29-1 test.

64-CAP

Carrierless Amplitude/Phase Modulation with a 64-state constellation pattern.

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Master Glossary – A

A
AAC

ACCULINK Access Controller. A T1 product which permits connection to a variety of
network services.

AAL

ATM Adaptation Layer. The layer above the ATM layer in the logical protocol stack, the AAL
translates a higher-layer service format into ATM cells.

AAL-1

The ITU-T classification for an ATM Adaptation Layer (AAL) that supports constant bit rate
(Class A), time-dependent data traffic. Also known as circuit emulation.

AAL-2

Not entirely specified, this is the ITU-T classification for an ATM Adaptation Layer (AAL) that
supports variable bit rate (Class B) data traffic.

AAL-3/4

The ITU-T classification for an ATM Adaptation Layer (AAL) that supports variable bit rate,
connection-oriented (Class C) or connectionless (Class D), delay-tolerant data traffic.

AAL-5

The ITU-T classification for a simplified ATM Adaptation Layer (AAL) that supports
connection-oriented, delay-tolerant data traffic.

AAL connection

An association of higher-layer entities established by the ATM Adaptation Layer.

ABR

Available Bit Rate. An ATM layer service type in which feedback is sent to the end system to
limit traffic according to available bandwidth.

ACAMI

Alternate Channel Alternate Mark Inversion. A T1 line coding technique.

ACCA

Auto-Call Auto-Answer. A circuit restoration feature used on point-to-point telephone circuits
that allows a station to initiate a call automatically and respond to a call automatically over a
switched line.

access node

One of several DSLAMs that reside in a Network Access Provider Network.

Access Security

A major alarm signifying that a dial access security alarm is active. This is caused by
accessing the security information via the front panel.

ACCULINK®

A product family and a registered trademark of Paradyne.

ACR

Allowed Cell Rate. In ATM, a traffic management parameter that sets the cell transmission
rate for a connection based on network traffic conditions.

Activ

Active configuration area. The configuration option set that is currently active for the device.
Before a configuration option set becomes active, you must save the set to the Active
configuration area.

active alert

An alarm, abnormal status condition, or event occurrence that is currently being reported to
the NMS. Once the alert is cleared, it becomes a historical alert and is no longer considered
active by NMS.

adapter

Hardware that provides some transitional function between two or more devices.

address

A symbol (usually numeric) that identifies the interface attached to a network.

address mask

A 32-bit mask used to identify the network and local portions of an IP address.

ADPCM

Adaptive Differential Pulse Code Modulation. A low bit-rate audio encoding technique in
which the PCM input data is compared to a signal estimate, and the difference is encoded
based on recent values.

ADR

Alert-Driven Routine. A routine that is triggered for execution by the arrival of an alert to the
NMS.

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Master Glossary – A

ADSL

Asymmetric Digital Subscriber Line. A variety of DSL with which a higher data rate is
employed downstream (to the customer site) than upstream (to the service provider).
Varieties include ANSI T1.413, ITU 992.1 (G.DMT), ITU 992.2 (G.lite), ITU 992.3/4 (ADSL2)
and ITU 992.5 (ADSL2+).

ADSL2

A high speed ADSL technology defined by ITU G.992.3/4, capable of 12 Mbps downstream.

ADSL2+

A high speed ADSL technology defined by ITU G.992.5, capable of 24 Mbps downstream.

ADSL/R®

Asymmetric Digital Subscriber Line/ReachDSL. The trade name for a technology that allows
a modem or circuit to provide both ADSL and ReachDSL service.

ADTF

ACR Decrease Time Factor. In ATM, the time permitted between the sending of RM-cells
before the rate is decreased to the Initial Cell Rate (ICR).

AFI

Authority and Format Identifier. In ATM, the part of the network level address header that
describes the Initial Domain Identifier type.

agent

A software program housed within a managed network device, such as a host, gateway, or
terminal server. An agent stores management data and responds to the manager’s data
requests.

agent (SNMP)

A software program housed within a device to provide SNMP functionality. Each agent
stores management information and responds to the manager’s request for this information.

aggregate

To combine two or more bit streams into a single bit stream.

aggregate rate

The sum of the DTE rates.

AHFG

ATM-attached Host Functional Group. The class of capabilities of a host in a Multiprotocol
Over ATM environment.

AID

Access IDentifier. In TL1, the address of an entity in the network.

AIR

Additive Increase Rate. In ATM, the rate of increase in cell transmission rate.

AIRF

Additive Increase Rate Factor. In ATM, a signal calculated as AIR times Nrm over Peak Cell
Rate (AIR*Nrm/PCR).

AIS

Alarm Indication Signal. A signal transmitted downstream instead of the normal signal to
preserve transmission continuity and to indicate to the rest of the network that a fault exists.
Also called a Blue Alarm.

AIX

Advanced Interactive eXecutive. IBM’s implementation of UNIX.

alarm

An abnormal condition affecting communications equipment, usually requiring attention.
Major alarms indicate a service disruption; minor alarms are less severe, but are indications
of a developing problem.

Alarm Indication
Signal

A signal transmitted downstream instead of the normal signal to preserve transmission
continuity and to indicate to the rest of the network that a fault exists. Also called a Blue
Alarm.

alert

An occurrence of interest within the network. Alerts include alarms and changes of status
experienced by communications equipment.

alert export

A feature permitting the export of alert data to external systems.

alert filtering

A feature that times or judges each alert and passes it only if the alert exceeds the specified
duration threshold or other criteria.

alert group

A predefined collection of alerts used to manage alerts for filtering purposes. An alert group
may consist of one or more alerts.

alternate destination

A designated port, DLCI, and EDLCI that provides an alternate path for backup when the
primary link or path is out of service.

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Master Glossary – A

alternate port

The unused Port 1, either the V.35 or the EIA-232-D interface, that provides an aggregate
data path for an external dial backup unit.

AMI

Alternate Mark Inversion. A line coding technique used to accommodate the ones density
requirements of E1 or T1 lines.

Access Node.

analog bridge

A multiport broadcast polling bridge that is used to increase the number of dial backup units
available for multipoint backup. An analog bridge can be used at either a remote tributary
site or at the control modem site.

analog loop

A test in which the modem’s transmit VF signal is looped to its receiver.

analog signal

A type of signal composed of continuously variable values, used to transmit voice or data
over telephone lines.

ANSI

American National Standards Institute. A member of ISO, ANSI accredits and implements
standards.

ANSI T1.403

The ANSI specification that defines T1 operation.

ANSI T1.413 Issue 2

An ANSI specification that describes DMT line modulation, used for a version of ADSL.

Answer mode

The state of a modem that is ready to receive an incoming call.

answering

One of a device’s internal operational modes that indicates the device is receiving a request
to connect.

API

Application Program Interface. The facility provided with application software for its
customization, or for communication with other software.

APL

Analog Private Line. The private circuit used for data transmission. Also called 4-wire
private line, private line, or leased line.

APM

APplication Module. A circuit card that supports a particular application, such as
synchronous data or voice.

application

The use to which a device is put.

ARP

Address Resolution Protocol. Part of the TCP/IP suite, ARP dynamically links an IP address
with a physical hardware address.

ASCII

American Standard Code for Information Interchange. The standard for data transmission
over telephone lines. A 7-bit code establishes compatibility between data services. The
ASCII code consists of 32 control characters (nondisplayed) and 96 displayed characters.

ASCII
terminal/printer

A device that can be attached, either locally or remotely, to data communications equipment
to display or print alarm messages.

ASDS

ACCUNET Spectrum of Digital Services. An AT&T network service offering the alternatives
of fractional T1, 9.6, 56 or 64 Kbps (clear channel) digital, and analog access to a digital
core network.

ASP

Application Service Provider. A business that provides to multiple users access to an
application maintained at a central facility.

asymmetric rate

The ability of a device to transmit at a different rate than it receives.

asynchronous

Lacking concurrence, such as a data transmission synchronized by framing characters with
leading and trailing bits.

asynchronous data

Data that is formatted so it is synchronized by a transmission start bit at the beginning of a
character and one or more stop bits at the end.

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Master Glossary – A

asynchronous
transmission

Data transmission that is synchronized by a transmission start bit at the beginning of a
character (five to eight bits) and one or more stop bits at the end.

async terminal

Asynchronous terminal. A terminal such as the VT100 used for controlling computing
devices.

AT Command mode

The idle state prior to the device establishing a successful connection with a remote device.
It is from the AT Command mode that AT Commands are issued.

AT command set

A group of commands, issued from an asynchronous DTE, that allow control of the modem
while in Command mode. All commands must begin with the characters AT and end with a
carriage return.

AT command string

Several AT commands issued at once. The string is preceded by an AT prefix.

AT commands

The group of commands used to control and configure a device through a DTE, such as a
personal computer. The commands must begin with the characters AT and end with a
carriage return.

AT prefix

A prefix issued before AT commands that identifies the DTE’s data rate, parity, and
character length.

ATI

Asynchronous Terminal Interface. A menu-driven, VT100-compatible system for configuring
and managing a termination unit.

ATM

Asynchronous Transfer Mode. A high-speed, low-delay, connection-oriented switching and
multiplexing technique using 53-byte cells to transmit different types of data concurrently
across a single physical link.

ATM Forum

An international organization for the promotion and standardization of ATM.

ATM layer link

The connect of two entities at the ATM layer level of the logical protocol stack.

ATM link

A virtual path link or virtual channel link.

ATM switch

A high-capacity, cell-based switch in the carrier backbone network. It provides access,
multiplexing, and switching functions, permitting combined data, video, imaging, and voice
services on a single platform.

ATM traffic
descriptor

A list of traffic management parameters that characterizes a virtual connection, including
Peak Cell Rate (PCR), Sustainable Cell Rate (SCR), and Maximum Burst Size (MBS).

ATR

Automatic Trouble Reporting. A feature that allows the automatic reporting of alerts or
alarms to local or remote printers or terminals.

attenuation

The dissipation of the power of a transmitted signal as it travels over a wire.

ATU

ADSL Transmission Unit. Sometimes used broadly to mean any xDSL termination device.

ATU-C

ATU – Central Office. An ATU at the CO end of the local loop.

ATU-R

ATU – Remote. An ATU at the remote (customer premises) end of the local loop.

authentication
server

A server whose function is to authenticate and log an end-user’s access location.

authentication
Failure trap

An SNMP trap that indicates that the device has received an SNMP protocol message that
has not been properly authenticated.

autobaud

The mode in which the device automatically determines the asynchronous DTE data rate.

AutoBaud

A connection algorithm, agreed upon by a consortium of CLECs and manufacturers, for
SDSL transceivers using 2B1Q.

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Master Glossary – A

autobaud mode

The mode in which the access unit forces automatic redetermination of the DDS line rate
(56 or 64 Kbps) as soon as a valid DDS network signal is detected.

auto-configuration
(LMI)

A FrameSaver feature that simplifies configuration. The FrameSaver unit creates network
and port interface DLCIs that match DLCIs identified in an LMI response message, then
connects the network interface DLCIs with the port DLCIs.

auto-configuration
(ILMI)

A FrameSaver feature that simplifies configuration. Using VPI/VCI numbers returned from
an ILMI request on the network port or entered manually, the FrameSaver SLV 9580 DSU
creates and cross-connects associated DLCIs and EDLCIs.

automatic adaptive
equalization

Equalization of a transmission channel that is adjusted while signals are being transmitted
to adapt to changing line characteristics.

automatic answer

A capability to respond to a call received over a dial line.

automatic rate
control

A feature which allows modems to adjust their signaling rate based on current line
conditions.

automode

To change modulations or rates within a modulation when modems first connect. A modem
may automode to a different modulation than what it is configured for due to the limitations
of the remote modem, or automode to a lower rate due to unfavorable VF line conditions
during connection.

autorate

In analog modems, the ability to adjust to varying VF line conditions by changing the data
rate to a higher or lower rate after connection. The lowest rate the modem autorates to is
4800 bps; the highest possible rate depends on the modulation the modems connected
with. In V.34, the modems may autorate asymmetrically.

AutoRate

A feature that allows a DSL termination unit to train to the optimal line rate.

AVC

Aggregated Virtual Circuit. In multilink frame relay, a virtual circuit comprising one or more
independent virtual circuits.

AWG

American Wire Gauge. An indication of wire diameter. The heavier the gauge, the lower the
AWG number, and the lower the impedance.

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Master Glossary – B

B
B8ZS

Bipolar 8 Zero Substitution. Encoding scheme for transmitting clear channel signals over a
T1 line.

BAC

Broadband Access Concentrator. Another name for a DSLAM or BLC.

backbone

The main circuit that carries the data before it is split into extended circuits going to their
final destination. Often used to refer to the part of the network that joins LANs together.

backhaul

The act of, or mechanism for, transmission from a remote site to a central site.

backplane

A common bus at the rear of a nest or chassis that provides communications and power to
circuit card slots.

backup

The process of preserving copies of files on a different drive, directory, or medium to protect
against the destruction or loss of the original files in the event of hardware or system failure.

bandwidth

The range of frequencies that can be passed by a transmission medium, or the range of
electrical frequencies a device is capable of handling

baseband

A category of transmission in which a single signal is sent over a single medium without
frequency division.

basic NAT

Basic Network Address Translation. An implementation of NAT in which a group of external
addresses is reserved for dynamic mapping to private network addresses.

baud

A unit of signaling speed that is equal to the number of symbols per second. This is not
necessarily the same as bits per second, although the terms are frequently interchanged.

Committed burst size. In frame relay networks, the maximum amount of data the network
agrees to deliver in a particular time interval under normal conditions. Expressed in bits.

B-channel

ISDN Bearer Channel. A 56 or 64 Kbps channel that carries customer information like voice
calls, circuit-switched data, or packet-switched data.

Excess burst size. In frame relay networks, the maximum amount of uncommitted data over
the committed burst size that the network can attempt to deliver in a particular time interval.
Expressed in bits.

BECN

Backward Explicit Congestion Notification. A bit set and forwarded by the network to notify
users of data traffic congestion, sent in the opposite direction of the frame carrying the
BECN indicator or bit. Outbound frames may encounter congestion and be dropped.

Bell 103J

A standard for 300 bps data transmission.

Bell 212A

A standard for 1200 bps data transmission.

BER

Bit Error Rate. The number of bits in error over a given period compared to the number of
bits transmitted successfully.

BERT

Bit Error Rate Test. A local pattern test used to analyze the network circuit that causes the
device to transmit and monitor a test pattern.

BES

Bursty Error Seconds. A second in which more than one but less than 320 CRC6 error
events have occurred.

B-ICI

B-ISDN InterCarrier Interface. An ATM Forum interface specification for public ATM
networks.

bilateral loopback

A combination of the DTE and Digital Loopbacks operating simultaneously in the same
DSU.

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Master Glossary – B

BIOS

Basic Input/Output System. The program interface between the hardware and the operating
system of a PC.

bipolar signal

A signal in which successive ones (marks, pulses) are of alternating positive and negative
polarity, and in which a zero (space, no pulse) is of zero amplitude.

bis

Latin for twice. Used to distinguish the second version of a standard from other versions;
e.g., V.32bis.

B-ISDN

Broadband ISDN. A high-speed (over 1.544 Mbps) ISDN implementation that can include
multiprotocol services such as data, voice, and video in the same network.

bisync

Binary synchronous communications. An IBM communications protocol that has become an
industry standard. It uses a defined set of control characters and control-character
sequences for synchronized transmission of binary-coded data between stations in a data
communications system.

bit

Binary digit. The smallest unit of digital information, having a value of one or zero.

bit robbing

A method of transmitting signaling information by displacing a digit time slot at regular
intervals.

BitStorm®

The trade name for a series of IP DSLAMs and CPE.

BLC

Broadband Loop Carrier. Paradyne BLCs include 1U units and multi-slot chassis.

BLEC

Building Local Exchange Carrier. A telephone service provider whose equipment and
network are contained within a building or complex.

BLERT

BLock Error Rate Test. A local pattern test used to analyze the network circuit that causes
the device to transmit and monitor a test pattern.

block allocation
method

A method of allocating digital signal level 0 (DS0) channels as a group rather than
individually.

BNC

Bayonet Neil Concelman. A bayonet-type connector for coaxial cables.

BONDING

Bandwidth ON Demand INteroperability Group. A method for combining two B-channels
onto one channel, allowing more data to flow through an ISDN connection.

BOOTP

Bootstrap Protocol. Described in RFCs 951 and 1084, it is used for booting diskless nodes.

bps

Bits per second. Indicates the speed at which bits are transmitted across a data connection.

BPV

Bipolar Violation. In a bipolar signal, a one (mark, pulse) which has the same polarity as its
predecessor.

BRI

Basic Rate Interface. An ISDN service rate of 144 Kbps, provided as two B-channels of
64 Kbps each for data transfer and one D-channel of 16 Kbps for control and signaling.

bridge

A connection that allows the passing of data packets between two network segments.

bridge mode

A mode in which all ports are assigned to one digital-sharing group.

bridged tap

Any part of the local loop that is not in the direct electrical path between the CO and the
service user.

BRITE

Basic Rate Interface Transmission Extension. A device that extends ISDN functionality over
a T1 trunk.

broadband

A system requiring or providing communication channels with transmission rates in excess
of 64 Kbps.

broadcast

A method of transmission. The simultaneous transmission to two or more communicating
devices.

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Master Glossary – B

brouter

A device used as a bridge or router utilizing the SNMP protocol.

Burst Tolerance. The limit parameter of the Generic Cell Rate Algorithm (GCRA).

buffer

A temporary storage area used to compensate for differences in data flow rate when
transmitting data from one device to another.

bus

An assembly of conductors that carries signals to and from devices along its path.

busied out

One of a device’s operational states. When a device is in the busy out (or make busy) state,
it will not be able to answer calls. If the busied out device is on a rotary, the rotary will skip
the device when servicing incoming calls. A device that has its dial line busied out may
switch to the service line for further use.

busy

The state of a communications device when it is occupied with processing a call, or has
been made to appear that way. A device appears busy when its Tip and Ring signals are
joined together.

BVI

Bridge group Virtual Interface. A representation of a bridge group used to exchange packets
between the bridge group interface and routed interfaces.

byte

A sequence of successive bits (usually eight) handled as a unit in data transmission.

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Master Glossary – C

C
cabinet

A structure that houses carriers (usually a maximum of six).

cable binder

Multiple insulated copper pairs bundled together in the telephone network.

CAC

Connection Admission Control. The set of actions taken at SVC or PVC establishment to
determine whether the connection should be rejected.

campus

The grounds of an institution or business, comprising multiple buildings in close
geographical proximity.

CAP

Carrierless Amplitude and Phase Modulation. A transmission technology for implementing a
DSL. Transmit and receive signals are modulated into two wide-frequency bands using
passband modulation techniques.

capacitance

The property of an electric nonconductor that permits the storage of energy as a result of
electric displacement.

carrier

A continuous frequency signal that can be modulated by another signal that contains
information to be transmitted.

CAS

Channel Associated Signaling. A type of signaling in which the state of the circuit is denoted
by status bits appropriated from information packets. Also called Robbed Bit Signaling.

CAT3

Category 3. A level of unshielded twisted-pair wiring performance as defined by
EIA/TIA-568. CAT 3 cable is used for transmission speeds up to 20 Mbps.

CAT5

Category 5. A level of unshielded twisted-pair wiring performance as defined by
EIA/TIA-568. CAT 5 cable is used for transmission speeds up to 100 Mbps.

C-bit

One of several bits in a DS3 subframe used for parity checking, error reporting, and other
control functions.

CBR

Constant Bit Rate. An ATM service category with a guaranteed rate, used for video, voice,
and other applications to which timing is critical.

Cluster Controller. A device that handles remote communications for multiple async (or
other VT100-compatible) terminals or workstations.

Control Channel. The diagnostic interface between an NMS and a network device.

CCA

Circuit Card Assembly. A printed circuit board to which separate components are attached.

CCITT

Consultative Committee on International Telegraphy and Telephony. An advisory committee
established by the United Nations to recommend communications standards and policies. It
was renamed ITU in March 1993.

CCR

Current Cell Rate. In ATM, an RM-cell field set by the source to its own current Allowed Cell
Rate (ACR).

CCS

Common Channel Signaling. A type of signaling in which a group of circuits share a single
reserved signaling channel.

CCV

C-bit Coding Violation. A CP-bit parity error.

Carrier Detect. The received line signal detector. V.24 circuit 109.

CDF

Cutoff Decrease Factor. In ATM, a parameter that controls the decrease in Allowed Cell
Rate (ACR) in the Cell Rate Margin (CRM).

CDV

Cell Delay Variation. In ATM, differences in cells’ transmission times caused by buffering
and cell scheduling. Peak-to-peak CDV is a Quality of Service (QoS) delay parameter in
CBR and VBR services.

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Master Glossary – C

CDVT

Cell Delay Variation Tolerance. In ATM, the maximum CDV that can be tolerated by the
recipient.

cell

The unit of transmission in ATM. An ATM cell contains a 5-byte header and a 48-byte data
payload.

cell header

Protocol control information used at the ATM layer, providing flow control, addressing,
prioritization, and error control.

cell site

A facility that provides the equipment needed to establish wireless communication links.

central office

CO. The PSTN facility that houses one or more switches serving local telephone
subscribers.

CEPT

The European Conference of Postal and Telegraph Authorities. A European standards
organization.

CER

Cell Error Ratio. In ATM, the number of cells with errors relative to the total number of cells
transmitted.

CES

C-bit Errored Second. A second during which a CCV, OOF, or incoming AIS was detected.

CES

Circuit Emulation Service. A facility that extends a non-ATM circuit (such as T3 or E3) over
an ATM network.

CEU

Commercial End User.

CGA

Carrier Group Alarm. Indicates one of the following on the T1 interface: AIS (Blue alarm),
Yellow alarm, or LOS or OOF (Red alarm).

CGI

Common Gateway Interface. A standard for running programs on an HTTP server.

channel

A bidirectional DS0, voice, or data path, for electrical transmission between two or more
points. Also called a circuit, line, link, path, or facility.

channel allocation

Assigning specific DS0 channels in the device to specific interfaces (Network, DTE
Drop/Insert, etc.).

channel group

An end-to-end allocation of bandwidth in integer multiples of 64 Kbps in the range of
64 Kbps to 1536 Kbps.

channeling device

A device in which the data coming in to or going out of a certain port or ports is distributed to
or gathered from the devices attached to various other ports, such as multiplexers and
control modems on a multipoint circuit.

CHAP

Challenge Handshake Authentication Protocol. A security technique that allows a user
password to be encrypted for transmission.

character

A letter, figure, number, punctuation, or other symbol.

character echo

A way to check the accuracy of data transmission by sending (displaying) all the characters
being transmitted to the monitor.

chassis ground

Pin 1 of an EIA RS-232 interface.

checksum

A value transmitted with a data packet, used by the receiver to assess the fidelity of the data
received. It is created by adding the bytes or words of data, ignoring overflow.

Congestion Indicator. In ATM, an RM-cell field sent to a source to cause it to reduce its
Allowed Cell Rate (ACR).

CIR

Committed Information Rate. Less than or equal to the access rate, the CIR is used by the
service provider for rate enforcement when the network allocates bandwidth. When rates
exceed the CIR, frames may be discarded.

circuit

A logical connection between two devices.

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Master Glossary – C

circuit multiplexing

A proprietary method that provides the ability to multiplex the data of multiple DLCIs or data
coming from multiple frame relay devices onto a single DLCI, sharing a single PVC
connection.

circuit pack lock

A screw lock tab installed over a circuit card’s latch release tab to prevent the unit from
being removed without a tool.

CISPR

International Special Committee on Radio Interference. A technical committee of the
International Electrotechnical Commission (IEC).

clamping

A function of the DSU that forces the output signal to go low (Off) and causes the DSU to
ignore input signals.

Class 1 fax

A fax modem standard. Under Class 1 computer software handles most of the protocol,
compression, and conversion tasks.

Class 2 fax

A fax modem standard. Under Class 2 the modem handles most of the protocol,
compression, and conversion tasks as well as modulation, leaving the computer free for
other work.

CLEC

Competitive Local Exchange Carrier. A telecommunications service provider that competes
with an RBOC to provide local telephone service.

CLI

Command Line Interface. Used to access a DSL router’s internal interface to display status,
edit configuration settings, and access router tests.

client

A device that receives a specific service, such as database management, from a server.

CLLM

Consolidated Link Layer Management. An ANSI-defined method for sending Link Layer
messages to a node to warn of congestion or link failure.

CLP

Cell Loss Priority. A bit in the ATM header that identifies cells that can be discarded during
periods of congestion. Cells with a CLP of 1 have lower priority than cells with a CLP of 0.

CLR

Cell Loss Ratio. A network-specific Quality of Service (QoS) parameter in ATM, CLR is the
number of lost cells compared to the total number of cells transmitted.

cluster

Composite object containing a group of sites which have been aggregated together in order
to avoid icon overlap on the screen.

cluster controller

A device that controls communications processing for multiple terminals.

CMI

Control Mode Idle. A control signal sent over the DDS line to indicate that no data is being
sent.

CMR

Cell Misinsertion Rate. In ATM, the number of cells received that were not transmitted by the
proper source compared to the number of cells correctly received.

Concentrator Node.

CNIS

Calling Number Identification Service. A service package ordered from the service provider
that supports ISDN Caller ID.

Central Office/Central Site. The PSTN facility that houses one or more switches serving
local telephone subscribers.

coaxial cable

A transmission cable consisting of a conducting outer tube which encloses and is insulated
from an inner conducting core.

coding

A technique used to accommodate the ones density requirements of E1 lines.

collision

Occurs when two tributary DSUs transmit data onto the network at the same time. The
transmissions interfere with each other and neither is successfully received.

COM port

Communications port. A computer’s serial communications port used to transmit to and
receive data from a modem. The modem connects directly to this port.

29 July 2005

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Master Glossary – C

COMCODE

A code used when ordering AT&T or Lucent Technologies parts.

command button

An on-screen icon which is selectable with the mouse. Selection of a command button
invokes a specific pre-defined function from a full-feature workstation. Command buttons
are used to invoke application-specific commands and basic commands (e.g., logoff,
refresh, etc.).

Command mode

One of two modem operating modes. When in Command mode, the modem accepts
commands instead of transmitting or receiving data.

Committed Burst
Size

Bc. In frame relay networks, the maximum amount of data the network agrees to deliver in a
particular time interval under normal conditions. Expressed in bits.

Committed
Information Rate

Less than or equal to the access rate, the Committed Information Rate (CIR) is used by the
service provider for rate enforcement when the network allocates bandwidth. When rates
exceed the CIR, frames may be discarded.

Committed Rate
Measurement
Interval

Tc. In frame relay networks, the variable time interval during which only the Committed
Burst Size (Bc) plus the Excess Burst Size (Be) can be sent.

common carrier

A company that provides telecommunications transmission services.

community name

An identification used by an SNMP manager to grant an SNMP server access rights to a
MIB.

compandor

A combination of a compressor at one point in a communication path for reducing the
volume range of signals, followed by an expandor at another point for restoring the original
volume range. Usually its purpose is to improve the ratio of the signal to the interference in
the path between the compressor and expandor.

comparator

A circuit in a DSU or in external test equipment that compares or checks a generated
message for errors and indicates the result of the comparison.

composite object

An object on the network map that contains or is composed of other objects. For example, a
site may contain network devices.

compression

The encoding of redundant data to reduce the number of bits it is necessary to transmit.

COMSPHERE®

A proprietary product family name and a registered trademark of Paradyne.

concentrator node

A switch or multiplexer that resides in the core of the network, providing data transport.

configuration

The arrangement of a system or network as defined by the characteristics of its functional
units.

configuration
management

The storage, administration, and synchronization of data concerning a network; e.g., device,
facility, connectivity, user, and vendor data.

configuration option

Device software that sets specific operating parameters for the device. Sometimes referred
to as straps.

configuration
shortcuts

A feature that simplifies basic setup (configuration) of the access unit. Based upon the
application selected, the access unit automatically configures certain options like DLCIs
from information obtained from the network.

congestion

In a network, the state of having more traffic than capacity.

connected

The state of having one device linked to another for exchanging data.

connector

An outlet on equipment and cables that provides a connection.

constituent link

In multilink frame relay, one of the independent virtual circuits that forms an Aggregated
Virtual Circuit.

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29 July 2005

Master Glossary – C

control

A device that is, for diagnostic purposes, at the logical head of a hierarchical network. It is
the unit from which tests and commands are issued to other units on the same circuit. There
is only one control per link.

Controlled Slip
Seconds

A one-second interval containing one or more controlled slips. A controlled slip is the
replication or deletion of the payload bits of a DS1 frame, occurring when there is a timing
difference between a synchronous receiving terminal and the received signal.

CoS

Cost of Service.

Customer Premises.

CP-bit

A C-bit used to carry DS3-path parity information.

CPCS

Common Part Convergence Sublayer. A component of the ATM Adaptation Layer’s
Convergence Sublayer (CS) that is the same for all traffic types.

CPCS-SDU

Common Part Convergence Sublayer – Service Data Unit. A protocol data unit shipped to
the receiving ATM Adaptation Layer (AAL).

CPE

Customer Premises Equipment. Terminal equipment on the service user’s side of the
telecommunications network interface.

CPU

Central Processing Unit. The main or only computing device in a data processing system.

CPU fail

Central Processing Unit failure. A Self-Test Health message indicating a failure in the
device’s central processing unit.

CRC

Cyclic Redundancy Check. A mathematical method of confirming the integrity of received
digital data.

CRC4

CRC using four check bits.

CRC5

CRC using five check bits.

CRC6

CRC using six check bits.

CRM

Cell Rate Margin. The difference in cells per second between the effective bandwidth and
the bandwidth allocated to cell transmission.

crossed pairs

When the DDS receive and transmit pairs are crossed, a facility alarm is generated.

crosstalk

Line distortion due to wire pairs in the same bundle being used for separate signal
transmission.

CRS

Cell Relay Service. An implementation of ATM standards.

Convergence Sublayer. The upper half of the ATM Adaptation Layer (AAL), which performs
the conversion between ATM and non-ATM formats.

CSA

Canadian Standards Association.

CSA

Carrier Serving Area. The loops extending a limited distance (up to 9,000 feet using
26 AWG unloaded twisted pair wiring or 12,000 feet using 24 AWG) from a CO or a DLC.

CSES

C-bit Severely Errored Second. A second during which 44 or more CCVs were detected, or
an OOF or an incoming AIS was detected.

CSS

Controlled Slip Seconds. A period in which a frame was added or deleted because of a
variance in timing.

CSU

Channel Service Unit. A device that connects service user equipment such as a DSU to the
local digital telephone loop, protects the line from damage, and regenerates the signal.

CTAG

Correlation Tag. In TL1, a unique identifier used to correlate a response message and an
input command.

29 July 2005

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Master Glossary – C

CTD

Cell Transfer Delay. The time it takes a cell to go from one ATM node to another.

CTS

Clear To Send. A signal indicating that the device is ready for the DTE to transmit data.
Usually occurs in response to Request To Send (RTS).

cut-through access

A type of access or terminal emulation from a window or an NMS to another computer
system.

Code Violation. Detected when using HDB3 coding format, this is equivalent to a BPV when
using AMI coding.

CVC

Constituent Virtual Circuit. In multilink frame relay, one of the independent virtual circuits
that forms an Aggregated Virtual Circuit.

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29 July 2005

Master Glossary – D

D
D4

The transmission standard that specifies 12 frames as a superframe that is used for frame
synchronization and to locate signaling bits.

DAA

Data Access Arrangement. Hardware that acts as a protective interface between the
telephone circuit and the modem. It performs such functions as ring detection, DC isolation,
and surge protection to protect the circuit from being disturbed by a modem malfunction.

DACS

Digital Access and Cross-connect System. A device that allows DS0 channels to be
individually rerouted and reconfigured.

daemon

An agent program that runs continuously on a server system and provides resources to
client systems on the network.

daisy chaining

Connecting the COM port of one device to the AUX port of another device to provide SNMP
connectivity.

data carrier

A continuous frequency signal that can be modulated by another signal that contains
information to be transmitted.

data compression

The elimination of empty fields, redundancies, and gaps in order to reduce storage capacity
needs and the amount of data to be transmitted. Anything that is compressed is restored
after the data is received.

Data mode

One of two general operating modes; the other is Command mode. When in Data mode, the
modem considers any input from the computer to be data and transmits it across the
telephone line to the remote modem.

data port

The electrical interface between the device and the synchronous data terminal equipment.

data rate

The speed at which data is transferred over the telephone line. This rate is measured in bits
per second.

data router

A sophisticated circuit switch in the DSU that is capable of connecting several
communication interfaces in more than one way, redirecting or routing data to an alternate
path.

database

An organized compilation of computerized data.

datagram

A data packet used to implement message transmissions between multiplexers and NMS;
these can include alerts, configuration, commands, etc.

dBm

A decibel referenced to one milliwatt into 600 ohms. This unit measures relative signal
power.

DBM

Dial Backup Module. The optional internal ISDN BRI feature that provides automatic dial
backup and service restoration of failed digital circuits. Provides an ISDN U-interface.

DCD

Data Carrier Detect. A signal passed from a local DCE to a local DTE when the DCE has
received an acceptable carrier signal over the line. Also known as RLSD (Received Line
Signal Detect).

DCE

Data Communications Equipment. The equipment that provides the functions required to
establish, maintain, and end a connection. It also provides the signal conversion required for
communication between the DTE and the network.

DCE Manager

See OpenLane.

D-channel

Data channel. The ISDN channel that carries signaling information to control call setup.

DCLB

Data Channel LoopBack. Loops the data received from the network interface, for all DS0
channels allocated to the selected port, back to the network.

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Master Glossary – D

DCP

Diagnostic Control Panel. The front panel of a device that continuously provides status
information about the device’s operation and allows an operator to manage its operation. A
generic term used for both the standalone and carrier-mounted models.

DDD

Direct Distance Dialing. Telephone exchange service, the public switched telephone
network (PSTN) that enables a telephone service user to access telephone lines without
operator assistance.

DDR

Data Delivery Ratio. The number of bytes received by a far-end device divided by the
number of bytes sent to it.

DDS

Digital Data Service, such as DATAPHONE Digital Service or ACCUNET Spectrum of
Digital Services, that provides private digital communication circuits.

Discard Eligibility. Part of the frame header that marks a frame for low priority if there is
congestion on the network. If congestion occurs, DE frames are the first to be discarded by
the network.

decompression

With a unit equipped with the data compression feature, compressed data coming from the
network is routed, decompressed, then serialized again for the DTE port.

default

A factory-preset value that is assumed to be correct unless changed by the user.

default route

The address used for routing packets whose destination is not in the routing table. In
Routing Information Protocol (RIP), this is IP address 0.0.0.0.

deiconification

The transformation of an iconified window back into a full-size window caused by clicking on
an icon.

DELT

Dual-Ended Loop Testing. A measure for obtaining diagnostic information about an ADSL2
loop with equipment connected at both ends.

demarc

The point of demarcation between a telephone communications facility and customer
equipment or wiring.

demodulation

The process of recovering data from a modulated carrier wave.

destination

The endpoint of a PVC connection, comprising a designated port, DLCI, and EDLCI.

DHCP

Dynamic Host Configuration Protocol. A Microsoft protocol for dynamically allocating IP
addresses.

DHCP Relay Agent

A system that detects and forwards DHCP discover or request messages to the appropriate
DHCP server.

DHCP server

A server which uses DHCP to allocate network addresses and deliver configuration
parameters to dynamically configured hosts.

diagnostic network

A network used for transmitting network control, monitoring, and testing information
between devices in the network and the network management system. It shares the same
physical transport facilities as the primary data network.

dial backup

A method of restoring service for data communications during a private line failure by
switching the data traffic to the public telephone network.

dial command
modifiers

A modifier used in the dial string that instructs the modem how to process a dialed
telephone number.

dial line

A communications circuit that is established by a switched circuit connection in the dial
network.

dial network

A public switched telephone network.

Dial Standby

One of a leased line device’s operational states. The Dial Standby mode allows the device
to switch back to leased line operation while still maintaining the dial line.

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Master Glossary – D

dial string

A series of characters that consists of numbers and modifiers used to dial a telephone
number.

dial-up

A temporary, as opposed to dedicated, connection between machines established over a
standard phone line.

dialog

A box or window that displays status or configuration information about an object or subject.

digital bridging

Provides the ability for dial backup of a multipoint configuration by bridging the signal on the
digital side of the front end panel.

Digital Loopback
Test

A local digital loopback test that connects the device’s receiver output back to the
transmitter input. This test disrupts the transmission of primary data.

digital signal

A signal composed of only two discrete values, representing the binary digits 0 and 1.

digital signal
processor (DSP)

A microprocessor designed to perform and execute mathematically intense calculations and
algorithms at high speeds, in real time, for various DSP applications. It is mostly used in
DSP applications involved in the sampling of a signal, such as digital filtering, speech
encoding, image processing, fast Fourier transforms, digital audio, and data transmission.

DIP switch

Dual In-line Package switch.

Digital Loopback. A test used for manual testing of the remote end of a circuit. For example,
a DL may be required to complete an external bit error rate test (BERT) from the remote
DSU. The local DSU receives test data, loops it back to the transmitter, and returns it to the
network.

DLB

DTE LoopBack. Loopback mode that loops the information received on the DTE T1 network
interface back to the network as close to the network interface as possible.

DLC

Digital Loop Carrier. Equipment that multiplexes telephone traffic over a single connection
between a central office and a business or residence.

DLCI

Data Link Connection Identifier. The virtual circuit number corresponding to a particular
connection between two destinations. This number is used as part of the frame relay
header. The total number of DLCIs between endpoints make up the PVC. DLCIs are a local
means of identifying a PVC.

D-lead control

A control signal method which causes the associated modem to go off-hook in the Originate
mode. With D-lead control signaling, a single signal lead is associated with each modem.
Momentary connection of this lead to common ground actuates the signal.

DLL

Dynamic Link Library. Unlike Terminate and Stay Resident applications, DLLs are
automatically loaded into memory when required and unloaded when space is needed for
other applications.

DMI

Data Mode Idle. Refers to a sequence of ones (marks, pulses) transmitted or received on
the DDS or Switched 56 Kbps network.

DMT

Discrete MultiTone. DSL technology using digital signal processors to divide the signal into
256 subchannels.

DNS

Domain Name System. An online distributed database that maps machine names into IP
addresses.

DOC

Canadian Department of Communication.

domain

A named group of machines on a network. In IP, a domain consists of a block of IP
addresses with similar prefixes.

doubleword

A pair of contiguous words. In microcomputers, a doubleword is four bytes long and usually
begins at an address evenly divisible by four.

29 July 2005

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Master Glossary – D

download

A process that transfers device firmware and software from a locally attached PC to a
device, or allows the duplication of firmware and software from a local device to a remote
device.

downstream

In the direction of the customer premises.

downstream

In extended networks, the direction in which diagnostic messages flow from the diagnostic
control site to any intermediate links and then to the final tributary modem.

downstream device

A device that is connected farther from the host computer.

DRAM

Dynamic Random Access Memory. The readable and writable memory used to store data in
PCs and other devices. Usually slower than SRAM, DRAM must also be regularly
refreshed.

driver

A software module that controls an input/output port or external device such as a keyboard
or a monitor. TCP/IP uses a driver to control the network interface cards.

drop

A tributary site.

drop/insert

An interconnection point for terminals, multiplexers, and transmission facilities. Individual
channels may be inserted into the aggregate stream or dropped out to accommodate
specific applications.

DS0

Digital signal level 0 (zero). A 64 Kbps digital telecommunications signal or channel.

DS0 channel
allocation

Assigning specific DS0 channels in the E1 NTU to specific interfaces (HDSL Network,
G.703 DTE, etc.).

DS1

Digital Signal level 1. A digital signal transmitted at the rate of 1.544 Mbps in North America.

DS1/E1 MIB

Defines objects for managing E1 interfaces and supports the network and G.703 DTE
interfaces on the E1 NTU.

DS3

Digital Signal level 3. A digital signal transmitted at the rate of 44.746 Mbps in North
America.

DSA

Digital Switched Access (see IEC).

DSD

Digital sharing device.

DSL

Digital Subscriber Line or Digital Subscriber Loop. The non-loaded, local-loop copper
connection between the customer and the first node within the network.

DSLAM

Digital Subscriber Line Access Multiplexer. A platform for DSL modems that provides
high-speed data transmission over traditional twisted-pair wiring.

DSP

Digital Signal Processor. The microprocessor that handles line signaling in a modem.

DSR

Data Set Ready. A signal from the DCE to the DTE that indicates the DCE is turned ON and
connected to the DTE.

DSU

Data Service Unit. Data communications equipment that provides timing, signal
regeneration, and an interface to data terminal equipment. A subrate DSU/CSU is normally
referred to as a DSU.

DSU/CSU

Data Service Unit/Channel Service Unit. A device that combines the functions of a DSU and
a CSU. It connects Data Terminal Equipment to the digital network, protects the line from
damage, and regenerates the signal.

DSX-1

Digital Signal Cross Connect level 1. An interconnection point for terminals, multiplexers
and transmission facilities.

DTE

Data Terminal Equipment. The equipment, such as a computer or terminal, that provides
data in the form of digital signals for transmission.

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29 July 2005

Master Glossary – D

DTE Loopback

A test that allows you to test each port independently. This test loops the data path at the
DTE interface.

DTE Password

The password required by the device(s) with the security feature before access is permitted
to the DTE interface.

DTE Signals

The signals associated with Data Terminal Equipment (DTE) communications to a device.
Examples: Clear-to-Send, Data Terminal Ready.

DTLB

Data Terminal LoopBack. Loopback mode that loops the data for a particular synchronous
data port back to the port just before it is combined with the rest of the T1 data stream.

DTMF

Dual-Tone Multi-Frequency. A signaling method using two voice frequencies to designate
the tones used for touch-tone dialing, as distinguished from pulse dialing.

DTR

Data Terminal Ready. A signal from the DTE to the DCE, such as that sent via Pin 20 of the
EIA-232 interface (V.24 circuit 108/1, /2), that indicates the DTE is turned ON and
connected to the DCE.

DXI

Data eXchange Interface. The standard for transfer of information between a DTE and an
ATM DSU/CSU.

29 July 2005

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Master Glossary – E

E
E1

A wideband digital interface operating at 2.048 Mbps, defined by ITU recommendations
G.703 and G.704. It is used primarily outside North America.

A wideband digital interface operating at 34.368 Mbps. It is used primarily outside North
America.

EBS

Excess Burst Size. In frame relay networks, the maximum amount of uncommitted data over
the committed burst size that the network can attempt to deliver in a particular time interval.
Expressed in bits.

Error Correction. Common error-correction protocols are V.42, MNP4, MNP 10, and ETC.

edge device

A device capable of forwarding packets between an ATM interface and an unlike network,
such as Ethernet, based on data-link layer and network layer information.

EDL

Embedded Data Link. The 8 Kbps in-band performance channel that provides 4 Kbps of
user bandwidth for the support of an SNMP management link.

EDLCI

Embedded Data Link Connection Identifier. The number or frame relay address that
identifies an individual logical link/connection when a multiplexed DLCI has been selected
for the link. Using a proprietary method, the access unit aggregates multiple frame relay
DLCIs going to the same destination access unit.

EDP

Escape-based Diagnostic Protocol.

EEPROM

Electrically Erasable Programmable Read-Only Memory.

EER

Excessive Error Rate. An error rate that is greater than the threshold that has been
configured in the device.

EFCI

Explicit Forward Congestion Indication. An indicator in the ATM header set by a network
entity that has detected congestion or impending congestion.

EFM

Ethernet in the First Mile. The use of Ethernet starting at the customer premises in
subscriber access networks. This is achieved through various technologies, including those
based on the IEEE 802.3ah standard.

EFS

Error-Free Seconds. EFS is a measurement of the performance of a data carrier.

EGP

Exterior Gateway Protocol. Protocol that distributes routing information to the routers that
connect autonomous systems.

EIA

Electronic Industries Association. This organization provides standards for the data
communications industry to ensure uniformity of interface between DTEs and DCEs.

EIA RS-232

An Electronic Industries Association standard defining the 25-position interface between
data terminal equipment and data communications equipment.

EIA RS-366-A

An Electronic Industries Association standard defining the 25-position interface between
data terminal equipment and data communications automatic calling equipment.

EIA/TIA

Electronics Industries Association/Telecommunications Industry Association. This
organization provides standards for the data communications industry to ensure uniformity
of the interface between DTEs and DCEs.

EIA/TIA-578

An Electronic Industries Association standard for fax modems.

EIA-232-D

An Electronic Industries Association standard defining the 25-position interface between
data terminal equipment and data communications equipment.

EIA-232-E

An Electronic Industries Association standard defining the 25-position interface between
data terminal equipment and data communications equipment.

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Master Glossary – E

EIA-530-A

An Electronic Industries Association standard for a high-speed, 25-position, DCE/DTE
interface.

EIR

Excess Information Rate. In frame relay networks, the rate of transmission above the
insured rate. Calculated as the maximum information rate less the Committed Information
Rate (CIR).

elastic store

A form of buffering between collocated data communications devices in complex networks;
required to maintain timing synchronization for data transmission in the entire network.

E&M

Ear and Mouth. A signaling protocol used in telephony. An E&M card in the AAC controls
the flow of voice traffic.

EMI

ElectroMagnetic Interference. Radio frequency radiation produced by or affecting
high-speed data systems.

encapsulated

Protocol-created control information that is added to the data or frame which has been
broken into blocks or packets. The DTE constructs control packets and encapsulates user
data within those packets.

End-to-End Test

A pattern test run on local and remote devices simultaneously.

end station

In ATM networks, computers that provide an interface between ATM end stations and other
ATM or non-ATM end stations.

enterprise

A company overall, as distinguished from a corporate campus or other smaller subdivision.

enterprise MIB

A MIB consisting of objects unique to a specific company’s devices.

enterprise-specific
trap

A trap unique to a specific company’s devices.

EOC

Embedded Operations Channel. An in-band channel between DSL devices at the physical
layer, used for management data.

EON

End of Number.

EPD

Early Packet Discard. A packet dropping policy for ATM. In EPD, entire packets are dropped
when a certain threshold of buffer usage is reached.

EPROM

Erasable Programmable Read-Only Memory.

ERP

Electronic Resource Planning.

error

A discrepancy between a measured or computed value or condition and the true or
specified value or condition.

error control

An algorithm used to detect and correct data transmission errors.

errored second

A performance measurement reported during a test, defined as a second in which at least
one error has been detected.

Errored Seconds. A second with one or more ESF error events (one or more CRC6 error
events or OOFs).

escape mode

A special data pattern generated when signaling for minimum disruptive effect between
control and tributary diagnostic interactions, and when the network does not support
Switched mode network codes.

escape sequence

A defined sequence of characters that causes a modem to switch from Data mode to
Command mode.

ESD

ElectroStatic Discharge. An undesirable discharge of static electricity that can damage
equipment and degrade electrical circuitry.

29 July 2005

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Master Glossary – E

ESF

Extended SuperFrame. The T1 transmission standard that specifies 24 frames as an
extended superframe to be used for frame synchronization and to locate signaling bits.

ETC

Enhanced Throughput Cellular. A proprietary analog cellular transmission protocol.

EtherLoop®

The trade name for a technology that provides simultaneous voice and high-speed data
services over POTS using Ethernet.

Ethernet

A type of network that supports high-speed communication among systems. It is a widely
implemented standard for LANs. All hosts are connected to a coaxial cable where they
contend for network access using a Carrier Sense, Multiple Access with Collision Detection
(CSMA/CD) paradigm.

Ethernet address

Another name for MAC address. The unique fixed address of a piece of hardware, normally
set at the time of manufacture and used in LAN protocols.

ETSI

European Telecommunications Standardization Institute. An organization that produces
technical standards in the area of telecommunications.

European Union. Formerly known as the European Community, the EU is a confederation of
countries dedicated to a united Europe.

event

Within a network, an occurrence of interest that is reported via an event message.

Excess Burst Size

Be. In frame relay networks, the maximum amount of uncommitted data over the committed
burst size that the network can attempt to deliver in a particular time interval. Expressed in
bits.

excessive BPV

An excessive bipolar violation condition results when at least one invalid bipolar violation
has occurred every 20 milliseconds for 2 seconds. A Health and Status message (under the
Status branch/menu) is generated when this condition is detected.

export

The process that makes a file available so that other systems can access it.

extended network

The extension of a circuit where the tributary DCE is connected to a downstream (extended)
control DCE.

extended result
codes

An asynchronous message (in either numbers or words) that includes VF data rate and
error control information that the modem sends to the DTE after executing or trying to
execute a command.

external alarm

An alert-control DSU feature in which the DSU detects a positive voltage on either Pin 23
or 19, triggering an alarm.

extranet

The portion of an enterprise network that is publicly accessible from the Internet.

EXZ

EXcessive Zeros. An occurrence of more consecutive zeros than is allowed for the line
encoding technique.

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29 July 2005

Master Glossary – F

F
facility

A leased or dial transmission line.

factory defaults

A predetermined set of configuration options containing the optimum settings for operation
on asynchronous dial networks.

failure

An uncorrected hardware error.

fallback

Retraining at a lower rate or speed.

FAS

Frame Alignment Signal. A loss of signal (LOS) error detection.

fast select

An extended data field used on some packet types for X.25 facility.

fault

An accidental condition that causes a functional unit to fail to perform its required function.

FAW

Frame Alignment Word. A loss of synchronization error detection.

fax modem

A modem capable of emulating some features of a fax machine. Working under the control
of fax software, a fax modem can communicate with a fax machine or with another fax
modem.

fax software

A program or system of programs installed on a computer that allows a fax modem to send
and receive facsimile images.

FCC

Federal Communications Commission. The Board of Commissioners that regulates all
electrical communications that originate in the United States.

FCS

Frame Check Sequence. A value calculated at the sending and receiving end of a
connection to determine if errors have occurred in transmission of a frame.

FDDI

Fiber Distributed Data Interface. An ANSI 100 Mbps LAN standard for fiber optic cable
networks.

FDI

Feeder Distribution Interface. The point where cable bundles from a telephone switch are
connected to distribution cables that run to customer sites.

FDL

Facility Data Link. The selected framing bits in the ESF format used in a wide-area link that
are used for control, monitoring, and testing.

FDM

Frequency Division Multiplexing.

FDR

Frame Delivery Ratio. The number of frames received by a far-end device divided by the
number of frames sent to it.

FEBE

Far End Block Error. An indication sent to the transmitting node by the receiving node that a
received packet is in error.

FEC

Forward Error Correction. A method of error control for data transmission where the
receiving device can detect and correct a character or block of code containing a
predetermined number of erroneous bits.

FECN

Forward Explicit Congestion Notification. A bit set and forwarded by the network to notify
users of data traffic congestion, sent in the same direction of the frame carrying the FECN
indicator or bit. Inbound frames may encounter congestion and be dropped.

feeder node

The Interworking Packet Concentrator, which concentrates traffic from multiple LANs onto a
high-speed WAN interface.

FEP

Front-End Processor. A communications computer associated with a host computer that
manages the lines and routing of data through the network.

29 July 2005

GL-25

Master Glossary – F

ferrite choke

A device attached to a cable to reduce electromagnetic interference and ensure compliance
with FCC Part 15 rules.

FEXT

Far End CrossTalk. Crosstalk that occurs at the remote end of a link.

FFS

Flash File System. Software used to manage flash memory.

FGRD

Frame ground.

FIFO

First In, First Out. Specifies order of priority for queued entries.

file access

Allows users to work with a remote file as if the file is local.

file server

A process running on a computer that provides access to files on that computer to programs
running on remote machines.

filler panel

Installed in all carrier slots that do not have a circuit card installed, a filler panel prevents
accidental contact with the carrier backplane.

filter

A rule or set of rules applied to a specific interface to indicate whether a packet can be
forwarded or discarded.

filtering

The act of altering the information displayed on a user interface according to available or
selected options.

firmware

Software that has been temporarily or permanently loaded into read-only memory.

flash memory

A type of RAM that is maintained while the system it resides in is powered down, erasable in
its entirety rather than byte by byte.

flow control

A process in which devices stop and start the flow of data in a network to avoid losing data.

Feeder Node.

FPGA

Field Programmable Gate Array. A digital component whose logic can be reprogrammed
after manufacture.

fractional E1

Individual DS0 channels that may be sold separately or in groups to provide bandwidth that
is some fraction of the total E1 capability.

FRAD

Frame Relay Assembler/Disassembler. The frame relay equivalent of an X.25 PAD, a FRAD
connects non-frame relay devices to the frame relay network. It also provides encapsulation
and translation.

FRAG

Frame Relay Aggregation. This capability statistically multiplexes data streams from
independent sources onto a single frame relay connection.

frame

One identifiable group of data bits that includes a sequence of bits for control and
identification information.

frame relay

A high-speed connection-oriented packet switching WAN protocol using variable-length
frames.

Frame Relay Forum

An association of vendors, carriers, users, and consultants that creates standards for the
implementation of frame relay systems.

frame relay header

The DLCI identifier contained within the frame.

frame relay
switching

The ability to route frames based on the source port and frame relay header (DLCI). The
header contains a DLCI identifier that distinguishes the port for which the data is intended.

framer

A program or device that assembles and disassembles frames.

FrameSaver®

The trade name for a series of products providing service level management over frame
relay.

GL-26

29 July 2005

Master Glossary – F

framing

A technique that separates bits into discrete identifiable groups.

framing

A control procedure used with multiplexed digital channels where bits are inserted so the
receiver can identify time slots allocated to each subchannel.

FRAW

Frame Relay Aware. Said of an access unit that can read the frame relay header and route
the data internally to the correct port.

FR Discovery

Frame Relay Discovery. A configuration shortcut method for automatic PVC configuration
within the FrameSaver access unit.

FRF.5

An implementation agreement endorsed by the Frame Relay Forum and the ATM Forum
that describes frame relay and ATM PVC network interworking.

FRF.8

An implementation agreement endorsed by the Frame Relay Forum and the ATM Forum
that describes frame relay and ATM PVC service interworking.

FRF.15

An implementation agreement endorsed by the Frame Relay Forum that describes protocol
and procedures for DTE-to-DTE multilink frame relay.

FRF.16

An implementation agreement endorsed by the Frame Relay Forum that describes protocol
and procedures for User-to-Network Interface and Network-to-Network Interface multilink
frame relay.

FRoDSL

Frame Relay over DSL.

front panel

The portion of a device that continuously provides status information about the device’s
operation and allows an operator to manage its operation. A generic term used for both the
standalone and carrier-mounted models.

FRS

Frame Relay Service. A service providing frame relay transmission.

FT1

Fractional Timing 1. ANSI standard for DCLB tests.

FTP

File Transfer Protocol. A TCP/IP standard protocol that allows a user on one host to access
and transfer files to and from another host over a network, provided that the client supplies
a login identifier and password to the server.

full-duplex

The capability to transmit in two directions simultaneously.

FUNI

Frame-based User-to-Network Interface. A protocol developed by the ATM Forum to
connect ATM networks and existing frame relay equipment.

FXO

Foreign Exchange Office.

29 July 2005

GL-27

Master Glossary – G

G
G.703

An ITU-T recommendation for the physical and logical characteristics of hierarchical digital
devices.

G.704

An ITU-T recommendation for synchronous frame structures.

G.711

An ITU-T recommendation for the pulse code modulation of voice frequencies.

G.804

An ITU-T recommendation for ATM cell mapping.

G.991.2

An ITU-T recommendation for high speed DSL using TC PAM. Also known as G.shsdl.

G.992.1

An ITU-T recommendation for a type of ADSL. Also known as G.dmt.

G.992.2

An ITU-T recommendation for a type of ADSL. Also known as G.lite.

gateway

A communications device or program that passes data between networks having similar
functions but dissimilar implementations.

gateway address

The subnet that the end-user system is on.

Gigabyte or gigabytes. As a unit of memory measurement, a gigabyte is usually taken to
mean 1,073,741,824 (230) bytes.

GbE

Gigabit Ethernet.

Gbps

Gigabits per second. In data rates a gigabit is usually taken to mean 1,000,000,000 (109)
bits.

GCRA

Generic Cell Rate Algorithm. In ATM, a formula used to determine conformance to the traffic
contract of a connection.

G.dmt

A name for the line modulation specified by ITU recommendation G.992.1.

generator

A circuit in a DSU or in external test equipment that produces a continuous string or stream
of known data patterns.

Generic-Interface
Extension MIB

An extension to MIB II that defines additional objects for control of generic interfaces in
MIB II.

Get (SNMP)

A command providing read-only access to SNMP MIB objects.

GigE

Gigabit Ethernet.

G.lite

A name for the line modulation specified by ITU recommendation G.992.2.

GranDSLAM™

A high-density Paradyne DSLAM supporting a variety of DSL transport types and network
services.

GrandVIEW™

The trade name for an element management system that supports Paradyne products.

ground

A physical connection to earth or other reference point.

ground start

A supervisory signaling technique in which the CPE signals the CO that it is off-hook by
creating a zero-voltage condition.

Group III

A fax standard that specifies a rate of transmission of about one page per minute.

G.shdsl

A name for the ITU recommendation G.991.2. SHDSL stands for Single-pair High-speed
Digital Subscriber Line, and is designed as a replacement for SDSL, HDSL, and other DSL
services.

GL-28

29 July 2005

Master Glossary – G

G.shdsl.bis

A name for a draft ITU recommendation for enhanced SHDSL. It provides for higher data
rates than G.991.2, and other improvements.

29 July 2005

GL-29

Master Glossary – H

H
H0

A 384 Kbps channel comprising six contiguous DS0s.

H10

A 1472 Kbps channel comprising 23 DS0s.

H11

A 1536 Kbps channel comprising an entire T1 line (24 DS0s) except for an 8 Kbps framing
pattern. This is the North American primary rate.

H12

A 1920 Kbps channel comprising an entire E1 line (thirty 64 Kbps channels) except for a
64 Kbps framing and maintenance channel. This is the European primary rate.

H.320

An ITU-T recommendation regarding video conferencing over narrowband facilities such as
ISDN.

half duplex

The capability to transmit in two directions, but not simultaneously.

handshaking

The exchange of predetermined codes and signals (tones) to establish a connection
between two modems. During handshaking the modems determine the modulation, rate,
and type of error control they will use.

HDB3

High-Density Bipolar Three Zeros Substitution. A line coding technique used to
accommodate the ones density requirements of E1 lines.

HDLC

High-Level Data Link Control. A communications protocol defined by the International
Standards Organization (ISO).

HDSL

High-bit-rate Digital Subscriber Line. A technique for high bandwidth, bidirectional
transmission over copper wire for T1 and E1 services.

HDSL2

High-bit-rate Digital Subscriber Line, 2nd generation. An ANSI specification for high
bandwidth, bidirectional transmission over a single twisted pair.

header

The beginning of a frame or cell that bears management and addressing information.

HEC

Header Error Control. In ATM, a CRC byte in the cell header that permits error checking and
correction.

HomeLink

A feature that provides peer-to-peer communications for PCs attached to different MVL
modems at the customer premises.

HomePNA

Home Phone Networking Alliance. A consortium of companies working for the adoption of a
single standard for networking over a home phoneline.

hop

One of the host-to-host links that forms the route between two hosts in a network. Two hosts
with one hop between them have no intervening host.

host

An addressable computer attached to a network.

host route

An IP address with a subnet mask of 255.255.255.255.

Hotwire®

The Paradyne registered trademark for its series of DSL and MVL products.

HSD

High-Speed Digital. A leased line service.

HSSI

High-Speed Serial Interface. An electrical interface supporting serial bit rates up to
52 Mbps.

HTML

HyperText Markup Language. The document format most widely used on the World Wide
Web.

HTTP

HyperText Transfer Protocol. An application-level protocol for the transmission of information
in distributed systems.

GL-30

29 July 2005

Master Glossary – H

hub

A device connecting several computers to a LAN.

hybrid management

An endpoint management facility permitting access to the endpoint from a DSL provider's
network operations center using the same management PVC used to manage the DSLAM.
It is useful when the network service provider, not the DSL provider, owns the endpoint.

Hertz. A unit of frequency that equals one cycle per second.

29 July 2005

GL-31

Master Glossary – I

I
I.356

An ITU-T specification for ATM traffic measurement.

I.361

An ITU-T specification for the B-ISDN ATM layer.

I.362

An ITU-T functional description of the ATM Adaptation Layer (AAL).

I.363

An ITU-T specification for the ATM Adaptation Layer (AAL).

IAB

Internet Architectural Board. Chartered by the Internet Society (ISOC), the IAB defines the
architecture of the Internet and provides technical guidance to the ISOC and the IETF.

IAC

Integrated Access Concentrator. An access gateway providing aggregation and switching
for multiple DSL connections.

IAD

Integrated Access Device. Customer premises equipment used for aggregrating diverse
traffic types, such as voice and data.

IBF

In-Band Framing. See bit robbing.

IBMC

In-Band Management Channel. A facility for managing DSLAMs, line cards, and endpoints
using a DS0 timeslot.

ICMP

Internet Control Management Protocol. Internet protocol that allows for the generation of
error messages, tests packets, and information messages related to IP.

iconification

The transformation of a window into a small rectangular object on the screen caused by
clicking on the iconify icon.

ICP cell

IMA Control Protocol cell. Used by the receiver in an IMA arrangement to maintain protocol
and link delay synchronization.

ICR

Initial Cell Rate. In ATM, the number of cells per second a source should transmit initially
and after an idle period. ICR is an Available Bit Rate service parameter.

IDC

Insulation Displacement Connector. A type of wiring terminal requiring no stripping of wire
insulation.

identity

Information about a particular data communications device, including the serial number,
model number and software version number.

idle state

A state in which the modem’s configuration options can be modified or commands can be
issued to the modem using AT commands.

IDSL

ISDN DSL using 2B1Q line code.

IEC

InterExchange Carrier. A company that provides inter-LATA (local exchange carrier)
telecommunications services, like AT&T, MCI, and US SPRINT. Access to these services
can be provided through DDS dedicated channels, T1.5 dedicated access channels, or
digital switched access (DSA) channels.

IEC

International Electrotechnical Commission. An international organization for the promotion
of standards and conformity in electrotechnology.

IEC connector

A connector specified by the International Electrotechnical Commission (an organization
which recommends technical standards).

IEEE

Institute of Electrical and Electronic Engineers.

IEEE 802.1Q

A standard that defines VLAN bridges.

IEEE 802.3

A standard for a LAN protocol suite, implemented as Ethernet.

GL-32

29 July 2005

Master Glossary – I

IETF

Internet Engineering Task Force. An open international organization concerned with the
evolution of the Internet.

IGMP

Internet Group Management Protocol. The method by which a host notifies neighboring
routers of its multicast group membership.

ILEC

Incumbent Local Exchange Carrier. The primary regional carrier; in the U.S., an RBOC or
its descendant company.

ILM

In-Line Monitor.

ILMI

Integrated Local Management Interface. An ATM Forum specification for network
management between public and private networks.

IMA

Inverse Multiplexing for ATM. An ATM Forum specification for sending an ATM cell stream
over multiple physical links.

IMC

Internal Management Channel. Internal to the DSLAM, the IMC is the management
interface of the MCC card.

interface

A shared boundary between functional units.

interference

The disturbance of a transmitted signal by an outside source, such as crosstalk, which has
a frequency or harmonic frequency similar to the desired signal.

internet

An internetwork.

Internet

The worldwide internetwork, which predominantly uses the TCP/IP protocol suite.

Internet address

An Internet Protocol address that uniquely identifies a node on an internet.

internetwork

An interconnected group of networks (also called an internet).

interoperability

The ability of equipment from different vendors to communicate using common protocols.

intranet

A private network or internet using Internet standards and software, but protected from
public access.

Inventory Code

The status of the device in the network.

inverse ARP

Inverse Address Resolution Protocol. Also called InARP, a protocol that permits a frame
relay router at one end of a management PVC to acquire the address of the device at the
other end of the PVC through the PVC’s associated DLCI.

inverse multiplexer

A device which divides a high speed circuit into lower speed circuits for transmission of data
over a WAN.

I/O

Input/Output. The act or capability of reading or writing data.

I/O Base Address

Areas of memory the CPU uses to distinguish between the various peripheral devices
connected to the system when transferring or receiving data.

IOC

ISDN Ordering Code.

Internet Protocol. An open networking protocol used for internet packet delivery.

IP address

Internet Protocol address. The address assigned to an internet host.

IPC

Interworking Packet Concentrator. A device that concentrates traffic from multiple LANs
onto a high-speed WAN interface.

IPCP

Internet Protocol Control Protocol.

IPsec

A protocol providing secure IP communications, used in implementing virtual private
networks (VPNs).

29 July 2005

GL-33

Master Glossary – I

IPX

Internetwork Packet Exchange. A LAN communications protocol used to move data
between server and workstation programs running on different network nodes.

IRQ

Interrupt Request. An event that causes a computer to halt normal execution and start an
interrupt handler routine to service an I/O request.

ISA

Industry Standard Architecture. A standard for connections among a CPU, memory, and I/O
devices on a single computer chassis.

ISDN

Integrated Services Digital Network. Telecommunication service that uses digital
transmission and switching technology to provide voice and digital data communications on
a bearer channel (B-channel) while sending signaling on the data channel (D-channel).

ISO

International Standards Organization.

ISOC

Internet SOCiety. A worldwide organization of Internet experts that oversees such
Internet-related boards and task forces as the IAB and IETF.

ISP

Internet Service Provider. A vendor who provides direct access to the Internet.

ITU

International Telecommunications Union. The telecommunications agency of the United
Nations, established to provide standardized communications procedures and practices.
Before March 1993 it was called CCITT.

ITU-T

The Telecommunications Standardization Sector of the International Telecommunications
Union, an advisory committee established by the United Nations to recommend
communications standards and policies. Before March 1993 it was called CCITT.

ITU-TSS

International Telecommunications Union Telecommunications Standardization Sector. An
advisory committee established by the United Nations to recommend communications
standards and policies and allocate transmission frequencies. Before March 1993 it was
called CCITT.

IWF

InterWorking Function. A process for protocol conversion, or the entity that performs the
conversion.

IXC

IntereXchange Carrier. A provider of telecommunications services between exchanges or
LATAs.

GL-34

29 July 2005

Master Glossary – J

J
Jetstream®

The trade name for a series of integrated telephone communication devices providing voice
over broadband.

JM8

A jack used for leased-line networks. Pins 1 and 2 are the transmit pair and Pins 7 and 8 are
the receive pair.

K
kB

Kilobyte or kilobytes. As a unit of memory measurement, a kilobyte is usually taken to mean
1,024 (210) bytes.

Kbps

Kilobits per second. In data rates a kilobit is usually taken to mean 1,000 bits. Also
abbreviated kbps and Kb/s.

kft

Kilofeet. 1,000 feet.

kHz

Kilohertz. A unit of frequency equal to 1,000 cycles per second.

29 July 2005

GL-35

Master Glossary – L

L
L2TP

Layer 2 Tunneling Protocol. L2TP is a standard, defined in RFC 2661, for creating Virtual
Private Networks.

LADS

Local Area Data Set. Used to provide a point-to-point link between two devices (also called
LDM).

Lamp Test

A test to verify that all status indicators and the control panel’s LCD are operating.

LAN

Local Area Network. A privately owned and administered data communications network
limited to a small geographic area.

LAN adapter

A device that allows a serial device to be connected to a LAN.

LANE

LAN Emulation. A technique for the encapsulation and transmission of connectionless
protocols over connection-oriented networks.

LAPB

Link Access Procedure for Balanced mode (X.25). A modification of HDLC, LAPB is a
layer 2 protocol defined by the ITU-T.

LAPD

Link Access Procedure for the D-channel (ISDN). A layer 2 protocol defined by the ITU-T.

LAPF

Link Access Procedure for Frame mode bearer services. A layer 2 protocol defined by the
ITU-T.

last mile

The telephone line between the local telephone company and the customer premises; also
known as the local loop.

LATA

Local Access Transport Area. A region served by a local exchange carrier (LEC) that
consists of one or more area codes.

latching loopback

A loopback that is maintained until a specific release code is detected. A latching loopback
can only be initiated or terminated by the 64 Kbps clear channel network service provider.

latency

The time it takes to transfer data from its source to its destination.

layer

A logical level in the Open Systems Interconnection model.

Leaky Bucket. The Generic Cell Rate Algorithm (GCRA) in ATM.

LoopBack. A diagnostic test that sends data through a loop of circuitry.

LBO

Line Build-Out. The amount of attenuation of the transmitted signal that is used to
compensate for the length of wire between the transmitter and the receiver.

A small, low-cost modular connector used for fiber optic cable.

LCD

Liquid Crystal Display. Thin glass plates containing liquid crystal material. When voltage is
applied, the amount of light able to pass through the glass plates is altered so that
messages can be displayed.

LCD

Loss of Cell Delineation. An indication that the receiving equipment cannot identify the
boundaries of a cell.

LCP

Link Control Protocol.

LCV

Line Code Violation. A bipolar violation or excessive zeros error.

LDAP

Lightweight Directory Access Protocol. An IETF-defined protocol for searching and
updating directories.

LDIF

LDAP Data Interchange Format. A file format used to transfer information between directory
servers.

GL-36

29 July 2005

Master Glossary – L

LDM

Limited-Distance Modem (also called a local area data set or LADS).

Leaky Bucket

An analogy used by the ATM Forum to illustrate the Generic Cell Rate Algorithm (GCRA).

Leased

A device operating on a private line where no dialing is necessary to make the connection.
A dial device can be configured to run on a leased line. Some local leased-line devices can
be switched over to dial mode while attached to a leased line.

leased line

A private line connection exclusively for the user. No dialing is necessary.

LEC

Local Exchange Carrier. A company that provides intra-LATA (local access transport area)
telecommunications services.

LED

Light Emitting Diode. A light or status indicator that glows in response to the presence of a
certain condition (e.g., an alarm).

LES

Line Errored Second. A second during which one or more Coding Violations or Loss Of
Signals occurred.

link

The physical connection between one location and another used for data transmission.

link configuration

Provides a communication path between point-to-point or multipoint units for compatibility
with network operations.

link delay

The estimated roundtrip delay in a diagnostic link immediately downstream from the specific
modem.

link layer protocol

The protocol that regulates the communication between two network nodes.

link-level address

Address for a particular device that is a concatenation of network addresses. It begins with
the device immediately downstream from the starting device (control channel address),
includes all intermediate devices, and ends with the destination device. Also known as
sequential address.

link trap

A trap that identifies the condition of the communications interface (linkDown or linkUp
traps).

LIU

Line Interface Unit. A physical layer data transmitter and receiver.

Local Loopback. A diagnostic test in which data is looped through data communications
equipment from the DTE interface and back to the DTE.

LLB

Line LoopBack. A test in which the received signal on the network interface is looped back
to the network without change.

LMI

Local Management Interface. In frame relay, the standard set of procedures and messages
for link-management signaling (information exchange) between a DTE and the network.

Load Number. The portion of total load to be connected to a telephone loop used by the
labeled equipment.

LOC

Loss of Cell delineation. An indication that the receiving equipment cannot identify the
boundaries of a cell.

local analog
loopback

A test in which the modem’s transmit voice frequency (VF) signal is looped to its receiver.

local loop

A twisted-pair cable that connects the subscriber’s premises to the local switching office.

local loopback test

An analog loopback test that connects the device’s transmitter output back into the device’s
receiver input. The local loopback test is disruptive and will disconnect the local device from
a remote device. The remote device remains disconnected from the local device after the
test.

LOF

Loss of Frame. Occurs when a DS1 terminal is unable to synchronize on the DS1 signal for
some interval.

29 July 2005

GL-37

Master Glossary – L

LOFC

Loss Of Frame Count. The number of LOFs declared.

To perform a sequence of actions at a terminal that establishes a user’s communication with
the operating system and sets up default characteristics for the user’s terminal session.

log out

To terminate interactive communication with the operating system, and end a terminal
session.

long-form
addressing

Addressing scheme used in networks in which the addresses of all intermediate devices,
including the tributary modems, are included in the address of the downstream device.

long space
disconnect

A disconnect effected when the modem receives an extended space from a remote modem.
When a modem is commanded to disconnect, it transmits a continuous space to the
opposite modem before disconnecting.

loop start

A supervisory signaling technique in which the CPE signals the CO that it is off-hook by
closing a relay at the CO.

loopback

A diagnostic procedure that sends a test message back to its origination point. Used to test
various portions of a data link in order to isolate an equipment or data line problem.

LOP

Loss of Pointer. An indication that the receiving equipment cannot identify the start of a cell.

LOS

Loss of Signal. A digital line condition where there are no pulses.

LOSW

Loss Of Sync Word. A detected failure of synchronization.

LPDA

Link Problem Determination Aid. A series of testing procedures used in NetView that are
initiated by the network control program (NCP) that provides the status of modems and
attached devices, and the overall quality of the link.

LQR

Link Quality Reports.

LSD

Line Signal Detect. A signal between the DTE and the DCE indicating energy exists on the
transmission circuit.

Line Termination. In ADSL, the CO line interface.

LTU

Line Termination Unit. The control unit on the network end of a link. (The NTU is on the
customer premises end.)

GL-38

29 July 2005

Master Glossary – M

M
M1

Management interface 1. An ATM Forum term for the management of ATM end devices.

M13

A system for multiplexing DS1 circuits into a DS3 circuit.

Management interface 2. An ATM Forum term for the management of private ATM networks
or switches.

Management interface 3. An ATM Forum term for the management of links between private
and public networks.

Management interface 4. An ATM Forum term for the management of public ATM networks.

Management interface 5. An ATM Forum term for the management of links between two
public networks.

MAC

Media Access Control. The lower of the two sublayers of the data link layer, the MAC
sublayer controls access to shared media.

MAC address

Media Access Control address. The unique fixed address of a piece of hardware, normally
set at the time of manufacture and used in LAN protocols.

manager (SNMP)

The device that queries agents for management information, or receives unsolicited
messages (traps) indicating the occurrence of specific events.

margin (DSL)

The additional noise, measured in dB, that would need to be added to the existing noise on
a given DSL loop to bring the Bit Error Rate to IE-7 (107).

Megabyte or megabytes. As a unit of memory measurement, a megabyte is usually taken to
mean 1,048,576 (220) bytes.

Mbps

Megabits per second. In data rates a megabit is usually taken to mean 1,000,000 (106) bits.

MBS

Maximum Burst Size. In ATM, the number of cells that may be transmitted at the peak rate
without violating the Generic Cell Rate Algorithm (GCRA).

MCC

Management Communications Controller. The circuit card used to configure and monitor
Paradyne Hotwire 8600 and 8800 series DSLAMs.

MCDV

Maximum Cell Delay Variance. In ATM, this is the uppermost CDV objective for the service
category.

MCLR

Maximum Cell Loss Ratio. In ATM, the upper limit of the number of cells lost compared to
the total number of cells.

MCP

Management Communications Processor. The circuit card used to provide consolidated
management access for DSL cards in a DSLAM.

MCR

Minimum Cell Rate. In ATM, the rate expressed in cells per second that the source is always
allowed to send.

MCTD

Maximum Cell Transfer Delay. In ATM, the sum of the Maximum Cell Delay Variance
(MCDV) and the fixed delay across the link or node.

MCU

Multi-Commercial Unit. A building or complex with commercial tenants, such as an office
building or shopping mall.

MDF

Main Distribution Frame. The point where all local loops are terminated at a central office.

MDI

Medium-Dependent Interface. A connection for twisted-pair cabling in Ethernet devices.
MDI-to-MDI connections require a crossover cable; MDI to MDIX connections require a
straight-through cable.

29 July 2005

GL-39

Master Glossary – M

MDIX

Medium-Dependent Interface Crossover. A connection for twisted-pair cabling in Ethernet
devices. MDIX-to-MDIX connections require a crossover cable; MDIX to MDI connections
require a straight-through cable.

MDU

Multi-Dwelling Unit. A building housing multiple residences, such as an apartment building.

menu tree

The structure containing the menu hierarchy starting at a Top-Level menu and extending
down to various device functions.

mesh network

A network configuration in which each node has a path to every other node.

MFA

Multiframe Alarm. A condition in which two consecutive multiframe alignment signals are
received in error.

MFR

Multilink Frame Relay. A method for aggregating multiple logical or physical links into a
single virtual circuit.

M-frame

A cyclic set of uniquely identifiable consecutive M-subframes.

M/HDSL

Multirate High-bit-rate Digital Subscriber Line. (See HDSL.)

MHU

Multi-Hospitality Unit or Multi-Hotel Unit. A hotel or motel.

MIB

Management Information Base. A database of managed objects used by SNMP to provide
network management information and device control.

MIB II

MIB Release 2. The current Internet-standard MIB, defined by RFC 1213.

MI/MIC

Mode Indicate and Mode Indicate Common. A control signal method which causes the
associated modem to go off-hook in the Originate mode.

MIR

Maximum Information Rate. In ATM, the rate of cell transmission that the source may never
exceed. Also known as Peak Cell Rate (PCR).

mixed inbound rates

In a multipoint network, several different data rates from tributary modems’ transmitters
communicating with one control modem.

MLP

MultiLink Protocol. A technique for combining B-channels to increase bandwidth for a
connection.

MMF

MultiMode Fiber optic cable. Fiber optic cable in which light is transmitted over multiple
paths.

mnemonic
addressing

The identification of system components by a customer-defined, easy to remember,
alphanumeric name, such as tokyo1.

MNP

Microcom Networking Protocol. Levels 2–4 of this protocol, similar to ITU V.42, detect and
correct data errors caused by telephone line noise and signal distortion. Level 5, similar to
ITU V.42bis, includes data compression.

MNP 10

Microcom Networking Protocol 10. A Microcom proprietary error-correction protocol for
cellular communications.

mobile switching
center

A facility that provides overall control for a wireless communication system. Cell sites are
linked to the public telephone network through a mobile switching center.

mode

Mode of operation for the DSU based on settings in effect and additional installed hardware
features.

modem

MOdulator/DEModulator. A device used to convert data from a digital signal to an analog
signal so that data can be transmitted over a telephone line. Once the data is received, the
analog signal is converted back into a digital signal.

modem bank

An organized array of dial modems, such as the modems loaded in an individual carrier.

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29 July 2005

Master Glossary – M

modem modulation

A set of guidelines that determines how the modems connect and at what speed they
communicate. Modulations, such as V.32bis and Bell 103, have a maximum and minimum
data rate. See also data rate.

modem pool

A number of modems grouped logically such that individual modems are accessible
according to availability by addressing the group.

modem port

The connection or interface between the modem and the telephone line.

modulation

The process of varying some characteristics (usually amplitude, frequency, and/or phase) of
a carrier wave to form data transmissions.

module

A compact assembly functioning as a component in a larger system or unit.

MPEG

Motion Picture Experts Group. An ISO committee that develops standards for digital video
and audio, including MPEG Audio Layer-3 (MP3).

MPLS

Multi-Protocol Label Switching. An IETF standard for using fast switching techniques like
ATM and frame relay over an IP network.

MRU

Maximum Request Unit.

MSA

Multiservices Access. Used to refer to a single platform that supports a variety of
applications, such as frame relay, synchronous data, and analog and digital voice.

M/SDSL

Multirate Symmetric Digital Subscriber Line. (See SDSL.)

MSO

Multiple System Operator. A TV cable company that operates more than one cable system.

M-subframe

A cyclic set of uniquely identifiable consecutive time slots.

MTBF

Mean Time Between Failures.

MTM

Multimedia Traffic Management. A suite of features that allow providers to identify multiple
services or applications, and apply intelligent service delivery and traffic steering.

MTSO

Mobile Telephone Switching Office. A generic name for the main cellular switching center
which supports multiple base stations.

MTU

Maximum Transmission Unit. The largest unit of data that can be sent across a network.

MTU

Multi-Tenant Unit. A building housing multiple tenants, such as an office building.
Sometimes used as a generic term to encompass Multi-Commercial Units (MCUs),
Multi-Dwelling Units (MDUs), and Multi-Hospitality Units (MHUs).

Mu-law

Normally written µlaw, a mathematical function used to encode audio for transmission.

multicasting

The ability of a network node to send identical data to a number of endpoints.

multiframe

An ordered, functional sequence of frames on a multiplexed digital circuit.

multi-homed host

A computer connected to more than one physical data link.

multilink frame
relay

The splitting of a high-speed stream of frame relay traffic over multiple interfaces.

multiplexer

A device used to interleave or simultaneously transmit multiple independent data streams
into a single high-speed data stream. Multiplexing techniques include FDM (frequency
division multiplexing), TDM (time division multiplexing), and STDM (statistical time division
multiplexing).

multiplexing

A method for interleaving several access channels onto a single circuit for transmission over
the network.

29 July 2005

GL-41

Master Glossary – M

multipoint circuit

A special type of circuit where one control device communicates in a broadcast mode with
one or more tributary devices. Communication from a tributary device is always directly to
the control device, and not to any of the other tributary devices.

multipoint line

A circuit connecting one control modem with one or more tributary modems.

mux

Multiplexer. A device used to interleave or simultaneously transmit multiple independent
data streams into a single high-speed data stream. Multiplexing techniques include FDM
(frequency division multiplexing), TDM (time division multiplexing), and STDM (statistical
time division multiplexing).

MVIP

Multi-Vendor Integration Protocol. A standard for using a variety of devices on a single
computer chassis.

MVL®

Multiple Virtual Lines. A Paradyne proprietary local loop access technology that permits
several services to concurrently and discretely use a single copper wire loop.

MVL card

A card with MVL ports used in Paradyne Hotwire 8600 Series and 8800 Series DSLAMs.

MVL modem

An endpoint (customer premises) modem that provides high-speed Internet or corporate
LAN access over twisted-pair copper lines using MVL technology.

GL-42

29 July 2005

Master Glossary – N

N
NAM

Network Access Module. It is a type of CCA that accesses or acts as an interface with the
network.

NAP

Network Access Provider. The provider of the physical network that permits connection of
service subscribers to NSPs.

NAPT

Network Address Port Translation. A type of NAT by which multiple hosts in a private
network can simultaneously access hosts in a remote network using a single IP address.

NAS

Network Access System.

NAT

Network Address Translation or Network Address Translator. A technique or device for
binding addresses in a private network with addresses in a global network to allow
transparent routing between the two domains. The two main variations of NAT are called
basic NAT and NAPT.

NDIS

Network Driver Interface Specification. Used for all communication with network adapters.
The specification was developed by Microsoft and 3Com to provide a common
programming interface for MAC drivers and transport drivers. NDIS works primarily with
LAN Manager and allows multiple protocol stacks to share a single network interface card.

Network Element. An addressable managed object.

NEBE

Near End Block Error. An indication that an error has been detected in a received packet.

NEBS

Network Equipment Building System. A set of requirements for the reliability and usability of
equipment, established by Bellcore (now Telcordia Technologies).

network

A configuration of data processing devices used for information exchange.

network address

A unique number associated with a host that identifies it to other hosts during network
transactions. This is the network portion of an IP address. In the Internet, assigned network
addresses are globally unique.

network data

The site profile data that describes the physical location of network devices and vendor
profile data that describes the providers of equipment, facilities, or services for the network.

network delay

The sum of all link delays downstream from a given modem.

network
management address

The customer-assigned diagnostic address of a modem.

Near End CrossTalk. Crosstalk in which the interfering signal is traveling in the opposite
direction as the desired signal.

NFS

Network File System. An application of IP developed by Sun Microsystems that permits one
computer to access another computer’s file system as if it were local.

NIC

Network Information Center. Assigns IP addresses and network numbers per request
submitted by an organization. The number assigned is appropriate to the number of host
devices on the network.

NIC

Network Interface Card. The circuit board or other hardware that provides the interface
between a DTE and a network.

NID

Network Interface Device. A device that connects the local loop to the customer premises
and includes the demarcation point.

NIM

Network Interface Module. The interface provided for the public switched telephone network
(PSTN). There are two NIMs per carrier.

29 July 2005

GL-43

Master Glossary – N

NMS

Network Management System. A computer system used for monitoring and controlling
network devices.

NMU

Network Monitoring Unit. A front-end microprocessor providing the diagnostic interface
between the modem network and the NMS processor.

NNI

Network-to-Network Interface. The point of connection of two frame relay networks.

NNI

Network Node Interface. The interface of ATM switches on different networks.

NOC

Network Operations Center. The point at which a network is monitored and controlled.

node

A connection or switching point on the network.

noise

The disturbance of a transmitted signal by an outside source of unlike frequency and
character, such as lightning.

nondisruptive
diagnostics

Diagnostics that are transmitted over the in-band secondary channel or routed through a
DBM in Standby mode so that primary data is not affected.

nondisruptive
session

A session in which executing commands will not disrupt primary data.

nonlatching
loopback

A loopback that is not maintained unless network loopback codes are interspersed with the
test data. A nonlatching loopback can only be initiated or terminated by the network service
provider.

nonlinear distortion

VF line distortion which is usually associated with pulse-code modulation (PCM)
compandor noise on the phone line.

nonvolatile

Memory that does not lose its contents when the device is powered down.

Nrm

In ATM, a Quality of Service (QoS) parameter denoting the maximum number of cells per
RM-cell that a source is allowed to send in the Available Bit Rate (ABR) service category.

nrt-VBR

Non-real-time Variable Bit Rate. An ATM service category that supports average and peak
traffic rate parameters, designed for applications with highly variable traffic.

NSP

Network Service Provider. A local telephone company or ISP that provides network services
to subscribers.

Network Termination. In ATM, the termination of a virtual channel or path at the
User-Network Interface. In ADSL, the customer premises line interface.

NTP

Network Time Protocol. A method for maintaining accurate local time with respect to radio
and atomic clocks on the Internet.

NTU

Network Termination Unit. The unit on the customer premises end of a link. (The LTU is on
the network end.)

NT1

Network Termination 1. In ISDN, the device the terminates the network at the customer
premises and provides a connection for terminal equipment.

NVRAM

Non-Volatile RAM.

Nx64

Usually pronounced “N by 64,” a number (N) of DS0s in aggregate forming a
high-bandwidth channel.

NxT1

Usually pronounced “N by T1,” a number (N) of T1s in aggregate forming a high-bandwidth
channel.

GL-44

29 July 2005

Master Glossary – O

O
OAM

Operations, Administration, and Maintenance. A group of network management functions in
ATM.

object (SNMP)

A specific item within a Management Information Base (MIB).

OCn

Optical Carrier level n signal. The fundamental transmission rate for SONET. OC3
represents a transmission rate of about 155 Mbps.

OCD

Out of Cell Delineation. When operating in direct mode, an OCD event is declared if seven
consecutive cells have header error control violations.

octet

Eight contiguous bits. Also known as a byte.

ODI

Open Data-link Interface. A standard architecture for device drivers and network interface
cards jointly developed by Novell and Apple.

off-hook

The state of a telephone or modem that is connected to the network.

offline

The state of a modem that is not connected to another modem.

on-hook

The state of a telephone or modem that is not connected to the network.

online

The state of a modem that is connected to and communicating with another modem.

Online Help

Assistance that is available by selecting Help from the current menu bar.

OOF

Out Of Frame. An error condition in which frame synchronization bits are in error.

OOS

Out Of Service. A digital network trouble signal reported by the remote unit.

OpenLane®

A standards-based network management system providing diagnostics, real-time
performance monitoring, historical reports, and health and status indications for Paradyne
SNMP-managed devices.

OpIQ

Operational Intelligence. A corporate goal that focuses on product and service
enhancements that lower the ongoing operational costs of a network through
solution-oriented network management, service and support, interoperability assurance,
and improved network security.

OSI

Open Systems Interconnection. The seven-layer architecture of data communication
protocols developed by ISO and ITU.

OSP

On-site Service Provider. A company that provides broadband service to an MDU or MTU.

OSS

Operations Support System. Software that facilitates management, planning, repair,
inventory, and provisioning in a service network.

29 July 2005

GL-45

Master Glossary – P

P
packet

A group of control and data characters that are switched as a unit within a communications
network.

PAD

Packet Assembly and Disassembly. The term PAD often is used with regard to X.25
networks; however, it can apply to any packet-switched network, such as frame relay.

PAP

Password Authentication Protocol. A security technique that requires a user password for
access to a system.

passband

A category of transmission in which multiple signals are sent over a single medium by
restricting channels to specific frequency ranges.

parity

A way of checking data accuracy by counting the number of bits that have a value of one.

partial backup

Partial backup on multipoint circuits is possible when not all tributaries are affected by a
network failure. The tributaries that are affected by the network failure communicate with the
control DSU through a backup connection.

pattern test

A local test causing the device to transmit and monitor for a particular test pattern. This test
disrupts the transmission of primary data.

payload

The user information bits in a frame, as distinguished from control and routing information.

P-bit

One of the bits carrying parity information for the preceding M-frame.

PBX

Private Branch Exchange. Telephone switching equipment dedicated to one customer. A
PBX connects private telephones to each other and to the public dial network.

Personal Computer.

PCC

Pseudo Carrier Control. Used by tributaries in a multipoint environment to communicate
with the control device via manipulation of the RTS Control Signal. Also known as V.13
signaling.

PCI

Peripheral Component Interconnect. A standard for a local bus used in most PCs.

PCM

Pulse Code Modulation. A method for encoding an analog signal onto a digital medium.

PCMCIA

Personal Computer Memory Card International Association. A standard used to define the
physical and operational characteristics of credit card-sized integrated circuits.

PCR

Peak Cell Rate. In ATM, the rate of cell transmission that the source may never exceed. Also
known as Maximum Information Rate (MIR).

PCV

P-bit Coding Violations. A received P-bit code that does not match the locally calculated
code.

PDP

Packet Dropping Policy. A strategy, such as EPD and PPD, for eliminating congestion in
ATM and IP networks.

PDH

Plesiochronous Digital Hierarchy. A network architecture developed for digitized voice over
twisted-pair cable.

PDU

Protocol Data Unit. A message containing protocol-specific information.

PDV

Pulse Density Violation. The number of ones (marks, pulses) is not adequate for the line
requirement.

PEC

Price Element Code. A code used when ordering parts.

peer address

An IP address used to indicate directly connected systems.

GL-46

29 July 2005

Master Glossary – P

peer entities

Entities at the same layer.

PEM

Power Entry Module. A module that provides 48V power isolation and distribution,
overcurrent protection, and power filtering and monitoring for the Hotwire 8820 GranDSLAM
chassis.

permissive interface

A dial modem operating mode characterized by a fixed output power level of –9 dBm. It is
one of two possible modes of operation for modems connected to dial lines.

PES

P-bit Errored Second. A second during which a PCV, OOF, or incoming AIS was detected.

Picofarads.

phase jitter

A rapid or repeated shifting of the relative phase of a signal resulting in unwanted distortion.

PHY

PHYsical layer. The physical medium connecting ATM devices.

PHY connection

An association between ATM entities established by the physical layer.

physical address

The diagnostic address of a control device derived from its location in the carrier; its carrier
and slot number.

ping

Named for its analogy to sonar, ping is a program that sends an echo packet to a specified
host, waits for a response, then reports the results of its operation. It is used for testing and
debugging networks.

ping

To verify the accessibility of a host or other device by sending it a message.

PLB

Payload LoopBack. Loopback mode that loops the information received on the T1 network
interface back to the network after it has passed through receive and transmit framing
section.

PLCP

Physical Layer Convergence Protocol. An IEEE-defined protocol for D3 transmission of
ATM.

PLD

Programmable Logic Device. A programmed integrated circuit, such as a PROM.

PLL

Phase Lock Loop. A timing mechanism in which timing information is sent in the data
stream.

PNNI

Private Network-Network Interface. A protocol that permits ATM switches from different
vendors to function on the same network.

POH

Path OverHead. A maintenance channel used in SONET.

point-to-multipoint
connection

In ATM, Virtual Channels or Virtual Paths representing a single root link and multiple leaf
nodes that can communicate with the root link but not with each other.

point-to-point circuit

A data network circuit with one control and one tributary device.

point-to-point
connection

Any connection with only two endpoints.

point-to-point line

A line or circuit connecting two stations.

poll list

A list containing the network management addresses of downstream modems.

polling

The continuous process by which NMS solicits network information network.

POP

Point Of Presence. The Network Service Provider’s access point on a Network Access
Provider’s network.

port

An access point for data entry or exit.

port aggregation

The feature that allows two ports to share a single frame relay link.

29 July 2005

GL-47

Master Glossary – P

POST

Power-On Self-Test. A test that checks most hardware components when power is applied
to the device or a reset is initiated.

POTS

Plain Old Telephone Service. Standard telephone service over the PSTN, with an analog
bandwidth of less than 4 kHz.

POTS splitter

A device that filters out the DSL signal and allows POTS frequencies to pass through.

power-on self-test

A test that checks most hardware components when power is applied to the device or a
reset is initiated.

PPD

Partial Packet Discard. A packet dropping policy for ATM. In PPD, cells in a packet following
a cell that must be dropped due to buffer overflow are also dropped.

PPP

Point-to-Point Protocol. A protocol for packet transmission over serial links, specified by
RFC 1661.

PPPoE

Point-to-Point Protocol over Ethernet. A method for establishing sessions and encapsulating
PPP packets over an Ethernet, specified by RFC 2516.

PPTP

Point-to-Point Tunneling Protocol. An extension of PPP used to create virtual private
networks of PCs running Windows NT.

PRBS

Pseudo-Random Bit Sequence. A test pattern containing any possible combination of digital
ones and zeros for a given string length.

PRI

Primary Rate Interface. An ISDN service rate of 1.544 Mbps (T1) or 2.048 Mbps (E1)
consisting of 23 (T1) or 30 (E1) B-channels and one signaling D-channel.

primary data
network

A network used to transport data from terminal to computer or from computer to computer. It
shares the same physical transmission facilities with the diagnostic network.

primary destination

A designated port, DLCI, and EDLCI for the primary data path from the data source so a
PVC connection can be established.

PRM

Performance Report Messages. Messages indicating the current state of a T1 line as
specified by ANSI-T1-403.

probe

Specialized agent software designed to gather a wide variety of statistical information about
network operation. The probe gathers the information, and the agent (the FrameSaver 9x24
unit) stores the statistical information locally.

programmable
interface

A dial modem operating mode characterized by an output power level (–12 to 0 dBm) set by
a programming resistor in the jack. It is one of two possible modes of operation for modems
connected to dial lines.

PROM

Programmable Read-Only Memory.

protocol

A set of rules that determines the behavior of devices in achieving and maintaining
communication.

protocol stack

The rules for timing, format, error control, and flow control during data transmission.

proxy ARP

Proxy Address Resolution Protocol. A technique for using a single network IP address for
multiple networks. A device responds to ARP requests with its own physical address, then
routes packets to the proper recipients.

PSC

Public Service Commission. State-level regulators of the local phone company in the United
States.

PSD

Power Spectral Density. The power in a specified bandwidth divided by the bandwidth. To
avoid crosstalk, DSL standards use a PSD mask to define by frequency what PSD may be
used.

PSES

P-bit Severely Errored Second. A second during which 44 or more PCVs were detected, or
an OOF or an incoming AIS was detected.

GL-48

29 July 2005

Master Glossary – P

PSTN

Public Switched Telephone Network. A network shared among many users who can use
telephones to establish connections between two points. Also known as dial network.

PTA

Postal and Telecommunications Administration. In The People’s Republic of China, a local
or provincial government-controlled communications authority.

PTT

Post, Telegraph, and Telephone. A national communications authority, sometimes
government-controlled and monopolistic, which acts as a common carrier.

pulse density

A measure of the number of ones (marks, pulses) in relation to the total number of bits
transmitted.

pulse dialing

One of two dialing methods in which telephone numbers are sent as pulses (brief changes
in voltage or current intensity) across the telephone line. Rotary telephones use pulse
dialing.

punchdown block

Used for connecting cable circuits of a network interface.

PVC

Permanent Virtual Circuit. A connection established administratively. Used in networks
supporting frame relay, X.25, and ATM.

PVC

Permanent Virtual Circuit. The DSU’s in-band management channel that supports remote
management via a Telnet connection. It is the logical link, identified by a DLCI, used for
routing frames over the network from their source to their destination.

PVC multiplexing

A patented method for multiplexing the data of multiple DLCIs onto a single DLCI to share a
single PVC connection.

29 July 2005

GL-49

Master Glossary – Q

Q
QAM

Quadrature Amplitude Modulation. A line code using phase and amplitude changes to send
digital data over an analog carrier.

QoS

Quality of Service. In ATM, a level of service dependent on Cell Loss Ratio (CLR), Cell
Transfer Delay (CTD), and Cell Delay Variation (CDV).

QRSS

Quasi-Random Signal Source. A test pattern simulating a random pattern of digital ones
and zeros used to simulate normal transmission.

GL-50

29 July 2005

Master Glossary – R

R
RADIUS

Remote Authentication Dial-In User Service. A user authentication protocol defined by
RFC 2058.

RADSL

Rate Adaptive Digital Subscriber Line. A technique for the use of an existing twisted-pair
line that permits simultaneous POTS and high-speed data communication at adaptive
symmetric and asymmetric rates.

RADSL card

A card with RADSL ports used in Paradyne Hotwire 8600 Series and 8800 Series DSLAMs.

RADSL modem

An endpoint (customer premises) modem that provides high-speed Internet or corporate
LAN access over twisted-pair copper lines using RADSL technology.

RAI

Remote Alarm Indication. A failure message sent by the remote unit in a link.

RAM

Random-Access Memory. Read/write memory that is volatile and loses its contents when
power is removed.

RAS

Remote Access Service. A Windows NT feature that permits the remote connection to a
server using ISDN, X.25, or standard telephone lines.

rate adaption

The ability to automatically adapt when the port speed is lower than the line speed.

RBOC

Regional Bell Operating Company. A Bell Operating Company in a particular geographic
area.

RBS

Robbed Bit Signaling. A type of signaling in which the state of the circuit is denoted by
status bits appropriated from information packets. Also called Channel Associated
Signaling.

Receive Data.

RDI

Remote Defect Indication. An LOS, LOF, or AIS defect detected on the far-end receiver.

ReachDSL®

A Paradyne proprietary subscriber line technology providing up to 1 Mbps throughput.
Compliant with ANSI T1.417, ReachDSL guarantees a minimum rate of 256 Kbps at 18 kft.

ReachDSL+

The trade name for a technology that allows a line card to provide both ADSL and
ReachDSL service.

receiver

A circuit that accepts data signals from a transmitter.

A part of the device’s memory that holds stored values.

Registry

In Microsoft Windows, the repository of information about users, applications, and
computers.

remote

Files, devices, and users not attached to your local DTE.

remote digital
loopback test

A request from the local device to the remote device to perform a remote digital loopback.
This test connects the remote digital receiver output back into the transmitter input. This test
disrupts the transmission of primary data.

remote host

The computer receiving the network command.

REN

Ringer Equivalence Number. A guide to help determine the number of devices that can be
connected to a telephone line.

reset

An initialization of the device that occurs at power-on or in response to a reset command.

response time

The elapsed time between a device receiving the first character of a message and the
receipt of the first character of the reply.

29 July 2005

GL-51

Master Glossary – R

result code

An asynchronous message (in either numbers or words) that the device sends to the DTE
after executing or trying to execute a command.

RFC

Request for Comments. One of the documents published by the Internet Engineering Task
Force that describe Internet protocols and policies.

RFC 1490-compliant

Standard of multiprotocol interconnect over frame relay. The encapsulation method for
carrying network interconnect traffic over a frame relay backbone; it also covers both
bridging and routing.

RFC 1695

An RFC self-described as definitions of managed objects for ATM management.

RFI

Radio Frequency Interference. Electromagnetic radiation generated by equipment during
normal operation that can interfere with neighboring equipment.

RIP

Routing Information Protocol. A protocol for exchanging routing information.

RISC

Reduced Instruction Set Computing. A computer architecture designed to achieve high
speed through use of a small number of simple machine instructions.

RJ11

A type of 6-position jack normally used with permissive dial networks and telephone sets.

RJ11C

A type of 6-position jack normally used with permissive dial networks and telephone sets.

RJ21

A type of 50-position jack normally used with permissive dial networks providing the
appropriate conductors for up to eight telephone lines.

RJ21X

A type of 50-position jack normally used with permissive dial networks providing the
appropriate conductors for up to eight telephone lines.

RJ27

A type of 50-position jack normally used with programmable dial networks providing the
appropriate conductors for up to eight telephone lines.

RJ45

A type of 8-position jack normally used with programmable dial networks.

RJ48C

An 8-position modular connector.

Remote digital Loopback. A test typically used when testing an external device. A test
message from the external device is looped back from the receiver to the transmitter in the
remote device and then returned to the local device. An RL puts the remote device into
Digital Loopback.

RLB

Repeater LoopBack. Loops the signal being sent to the network back to the DTE
Drop/Insert and data ports after it has passed through the framing circuitry of the device.

RLSD

Received Line Signal Detect. A signal passed from a local DCE to a local DTE when the
DCE has received an acceptable carrier signal over the line. Also known as Data Carrier
Detect (DCD).

Resource Management. The management of critical resources such as buffer space and
bandwidth in an ATM network.

RM-cell

Resource Management cell. In ATM, special cells sent to the source to convey information
about the state of the network.

RMA

Return Material Authorization. Provided by customer assistance center for equipment
return.

RMON

Remote MONitoring. A management standard that was developed to provide traffic
statistics and analysis for comprehensive network fault diagnosis, planning, and
performance tuning.

RMON1

Remote MONitoring, Version 1. A management standard that was developed to provide
traffic statistics and analysis for comprehensive network fault diagnosis, planning, and
performance tuning.

GL-52

29 July 2005

Master Glossary – R

RMON2

Remote MONitoring, Version 2. An industry standard used to remotely and proactively
monitor and troubleshoot switched networks at layers higher than the data link. RMON2 can
identify the server that sent a packet, the user the packet is going to, and the application that
the packet represents.

Read-Only.

ROM

Read-Only Memory. This is nonvolatile memory which cannot be written to. The modem’s
operational firmware is stored in this type of memory.

rotary

A telephone company service whereby multiple lines to a customer site share a common
telephone number.

router

A device that connects LANs by dynamically routing data according to destination and
available routes.

routing table

A table used by a node to route traffic to another node in the multiplexer network.

RS-232

An Electronic Industries Association’s standard for a low-speed, 25-position, DCE/DTE
interface.

RS-232-D

An Electronic Industries Association’s standard defining the 25-position interface between
data terminal equipment and data communications equipment.

RS-232-like MIB

RFC 1659, which defines objects for managing RS-232-type interfaces (e.g., RS-422,
RS-423, etc.) and supports synchronous data ports and management communication ports
on the device.

RS-449

An Electronic Industries Association’s standard for a general-purpose, 37-position,
DCE/DTE interface.

Remote Terminal.

RTS

Request To Send. A signal from the DTE to the DCE, indicating that the DTE has data to
send. V.24 circuit 105.

RTT

Round Trip Time. A measurement of the delay between two hosts.

RTU

Remote Termination Unit. A DSL device installed at the customer premises.

rt-VBR

Real-time Variable Bit Rate. An ATM service category that supports average and peak
traffic rate parameters, designed for applications with a low tolerance for delay and delay
variation.

Read-Write.

Receive. To obtain transmitted signals.

RXC

Receive Clock. V.24 circuit 115.

RXD

Receive Data.

29 July 2005

GL-53

Master Glossary – S

S
SA

Source Address. In ATM, the originator’s address.

SAR

Segmentation And Reassembly. The function of breaking apart or reassembling packets of
arbitrary size, or the entity that provides this function.

scheduling

The ability to mark a transaction or command for execution at a specific time and/or for
repeated execution.

SCR

Sustainable Cell Rate. The upper limit of the average rate of an ATM connection.

SCSI

Small Computer Serial Interface. A standard for electrical interfaces between a computer
and peripheral devices.

SCM

Shelf Concentration Module. A circuit card that provides connectivity between DSL devices
and an ATM uplink.

SDC

Synchronous Data Compression. A proprietary compression and error correction protocol.

SDCP

Shared Diagnostic Control Panel. A feature that allows carrier-mounted devices to share the
same diagnostic control panel.

SDH

Synchronous Digital Hierarchy. Based in part on SONET, SDH is an ITU standard for the
interworking of ANSI and ITU transmission techniques.

SDL

Supervisory Data Link. The connection between multiplexer nodes, used to pass network
control data.

SDLC

Synchronous Data Link Control. An IBM standard data link protocol.

SDSL

Symmetric Digital Subscriber Line. A technique for the use of an existing twisted-pair line
that permits high bandwidth, bidirectional transmission.

SDU

Service Data Unit. In ATM, interface information preserved from end to end in a layer
connection.

SDU

Shared Diagnostic Unit. A circuit card installed in Slot 0 of the COMSPHERE 3000 Series
Carrier that provides an interface between an optional SDCP or network management
system and the devices in the carrier.

secondary clock

The secondary clock source used to provide timing to the device when the primary clock
fails.

SEEP

Serial (interface) Electrically Erasable PROM. Also known as serial EEPROM.

SEFS

Severely Errored Frame Second. A second during which an OOF or an incoming AIS was
detected.

self-test

A test that checks most hardware components when power is applied to the device or a
reset is initiated.

SELT

Single-Ended Loop Testing. A measure for obtaining diagnostic information about an
ADSL2 loop with equipment connected only at one end.

sequential address

The concatenation of the network addresses of all nodes between two nodes, beginning
with the control channel address and ending with the node itself.

server

A device that offers a specific service, such as database management, to a client.

Service Level
Agreement

A contract between a frame relay service provider and a customer in which the service
provider guarantees a certain level or quality of service to the customer. Level of service is
defined by a set of measurable parameters, each having thresholds that are negotiated by
the service provider and customer.

GL-54

29 July 2005

Master Glossary – S

Service Level
Management

Managing and monitoring of network parameters to ensure Quality of Service as defined in
a Service Level Agreement between a network service provider and an end user. Includes
monitoring, diagnostics, and reporting of critical network parameters such as availability,
latency and throughput.

service network

A logical grouping of users regardless of their physical location on a network.

SES

Severely Errored Seconds. Usually defined as a second during which a specific number of
CRC errors was exceeded, or an OOF or other critical error occurred.

Set (SNMP)

A command providing write access to SNMP MIB objects.

Superframe. Also known as D4 framing, the T1 transmission standard that specifies
12 frames to be used for frame synchronization and to locate signaling bits.

SFP

Small Form-factor Pluggable. A specification for modular optical transceivers.

SGML

Standard Generalized Markup Language. An ISO standard language for the representation
of documents and the interrelationship of information in them.

SGRD

Signal Ground. Pin 7 of an EIA RS-232 interface.

Shared Diagnostic
Unit (SDU)

A circuit card that plugs into the control slot of a carrier to provide the shared diagnostic
control panel and network management interfaces to the devices in the carrier. It translates
the network management protocol to the devices in the carrier and routes incoming
messages to the appropriate slots.

SHDSL

A name for the ITU recommendation G.991.2. SHDSL stands for Single-pair High-speed
Digital Subscriber Loop, and is designed as a replacement for SDSL, HDSL, and other DSL
services.

short packet

A packet containing fewer than 80 bytes of data.

signal ground

Pin 7 of an EIA RS-232 interface.

SIM

System Interface Module. A module that provides user interface connections on the front of
the Hotwire 8820 GranDSLAM chassis.

SIP

SMDS Interface Protocol. A three-layer protocol implemented in SMDS networks.

SLA

Service Level Agreement. A contract between a frame relay service provider and a
customer in which the service provider guarantees a certain level or quality of service to the
customer. Level of service is defined by a set of measurable parameters, each having
thresholds that are negotiated by the service provider and customer.

SLIP

Serial Line Internet Protocol. Protocol for serial operation on an internet.

SLM

Service Level Management. Managing and monitoring of network parameters to ensure
Quality Of Service as defined in a Service Level Agreement between a network service
provider and an end user. Includes monitoring, diagnostics, and reporting of critical network
parameters such as availability, latency and throughput.

slot

A bay in the carrier into which a circuit card can be installed.

SLV

Service Level Verifier. A feature that monitors and ensures frame relay network service
levels.

SMDS

Switched Multimegabit Digital Services. A packet switching service connecting LANs.

SMF

Single Mode Fiber. Optical fiber in which light is transmitted over one path.

SMI

Structure of Management Information. SMI presents a prefix tree with defined object
identifiers.

Service Node. The endpoint modem at the customer premises, also known as a Remote
Termination Unit (RTU).

29 July 2005

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Master Glossary – S

Sequence Number. A 4-byte field in an ATM Resource Management cell (RM-cell)
representing the ITU-T I.371-defined sequence.

SNA

Systems Network Architecture. An IBM specification of layered protocols for communication
between programs, and between terminals and applications.

SNAP

SubNetwork Access Protocol. An IEEE-defined frame format used for TCP/IP and other
protocols.

SNAP

SubNetwork Attachment Point. The unique address of a host attached to a subnetwork.

SNMP

Simple Network Management Protocol. Protocol for open networking management.

SNMP agent

An application program that facilitates communication between an SNMP management
system and a device.

SNMP trap

A message sent to an SNMP manager to notify it of an event, such as a device being reset.

SNR

Signal-to-Noise Ratio. The ratio of the amplitude of a desired signal to the amplitude of
noise on the same carrier.

SOHO

Small Office/Home Office. Used to denote a single-building computing or networking
environment, as distinguished from a campus or enterprise environment.

SONET

Synchronous Optical NETwork. An ANSI standard for the transmission of digital data over
optical networks.

source-based routing

A security feature that ensures that all upstream traffic within a service domain is sent to the
Network Service Provider and not to another end-user system.

Spanning-Tree
Protocol

A link management protocol that provides path redundancy while preventing undesirable
loops in the network.

SPID

Service Profile Identification. A unique number assigned to an ISDN terminal that identifies
the ISDN services that have been configured for the terminal.

SRAM

Static Random Access Memory. The readable and writable memory used to store data in
PCs and other devices. Usually faster than DRAM, SRAM maintains its contents as long as
power is applied to it.

SRU

Signal Regenerator Unit. A repeater in an SHDSL span.

SSCS

Service Specific Convergence Sublayer. A component of the ATM Adaptation Layer’s
Convergence Sublayer (CS) that differs according to traffic type.

static route

A user-specified permanent entry in a routing table that takes precedence over routes
chosen by dynamic routing protocols.

status enquiry

Message sent by the customer’s frame relay equipment to maintain its user-network keep
alive process, and requesting a status from the network. Network responds to each status
enquiry frame.

STD

A subseries of RFCs that specify Internet standards. The official list of Internet standards is
in STD 1.

STM

Synchronous Transfer Mode. Transport and switching of digital data in a regular and fixed
pattern.

STM-1

Synchronous Transmission Module 1. The fundamental SDH transmission frame and
payload rate (155.52 Mbps).

StormTracker™

The trade name for an element management system that supports Paradyne products.

STP

Shielded Twisted Pair. A cable consisting of one or more pairs of wires twisted together and
wrapped with foil.

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29 July 2005

Master Glossary – S

STP

Spanning-Tree Protocol.

STS-1

Synchronous Transport Signal 1. The fundamental SONET transmission frame and payload
rate (51.84 Mbps).

STU-C

SHDSL Transceiver Unit, Central site.

STU-R

SHDSL Transceiver Unit, Remote terminal site.

Service User. The end user at the customer premises.

subnet

A portion of a network, which may be a physically independent network segment, that
shares a network address with other portions of the network and is distinguished by a
subnet number. A subnet is to a network what a network is to an internet.

subnet address

The subnet portion of an IP address. In a subnetted network, the host portion of an IP
address is split into a subnet portion and a host portion using an address (subnet) mask.
This allows a site to use a single IP network address for multiple physical networks.

subnet mask

A number that identifies the subnet portion of a network address. The subnet mask is a
32-bit Internet address written in dotted-decimal notation with all the 1s in the network and
subnet portions of the address.

subtend

To aggregate and service data from several sources.

SVC

Switched Virtual Circuit. In ATM, a connection established through signaling.

SWC

Service Wire Center. The location of the CO designated to provide service to a particular
customer premises.

switched 56 Kbps
digital service

A service provided by local exchange and interexchange carriers (LECs and IECs) that
allow customers to use high-speed switched digital data capability without having to
subscribe to private network services.

synchronous

Concurrent, such as a data transmission synchronized by a time signal that accompanies
the data.

synchronous data

Data transmission that is synchronized by timing signals. Characters are sent at a fixed rate.

synchronous
transmission

Transmission in which the data characters and bits are transmitted at a fixed rate with
transmitter and receiver synchronized. This eliminates the need for start and stop bits as
used in asynchronous transmission, and is thus faster and more efficient.

29 July 2005

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Master Glossary – T

T
T1

A term for a digital carrier facility used to transmit a DS1 formatted digital signal at
1.544 Mbps. It is used primarily in North America.

T1-PRI

T1 Primary Rate Interface. A DS1 configured for 23 bearer channels and one control
channel. Usually associated with ISDN, its bearer DS0s are suitable for audio, ITU-T
V.xx-series modulations, and clear channel synchronous data.

T1-RBS

T1 Robbed Bit Signaling. A DS1 configured for 24 bearer channels using robbed bit
signaling. Its DS0s are suitable for µlaw transport of audio, and ITU-T V.xx-series
modulations. Called DS1 service by some RBOCs.

A term for a digital carrier facility used to transmit a DS3 formatted digital signal at
44.746 Mbps. It is used primarily in North America.

TACACS

Terminal Access Controller Access Control System. A user authentication protocol defined
by RFC 927.

Committed Rate Measurement Interval. In frame relay networks, the variable time interval
during which only the Committed Burst Size (Bc) plus the Excess Burst Size (Be) can be
sent.

Transmission Convergence. The sublayer of the ATM layer that converts cells into a steady
flow of bits for transmission, and delineates cells received as a bit stream.

TCP

Transmission Control Protocol. An Internet standard transport layer protocol defined in
STD 7, RFC 793. It is connection-oriented and stream-oriented.

TC PAM

Trellis-Coded Pulse Amplitude Modulation. The modulation technique used for G.shdsl,
TC PAM produces little crosstalk when implemented in the same binder group with other
services, and is well suited for voice traffic.

TCP/IP

Transmission Control Protocol/Internet Protocol. The dominant protocol suite in the
worldwide Internet, TCP allows a process on one machine to send data to a process on
another machine using the IP. TCP can be used as a full-duplex or one-way simplex
connection.

TCS

Transmission Convergence Sublayer. The sublayer of the ATM layer that converts cells into
a steady flow of bits for transmission, and delineates cells received as a bit stream.

Transmit Data.

TDM

Time Division Multiplexer. A device that enables the simultaneous transmission of multiple
independent data streams into a single high-speed data stream by simultaneously sampling
the independent data streams and combining these samples to form the high-speed
stream.

Terminal Equipment. The endpoint of an ATM connection.

Telnet

Virtual terminal protocol in the Internet suite of protocols. Allows the user of one host
computer to log into a remote host computer and interact as a normal terminal user of the
remote host.

ter

Latin for thrice. Used to denote the third version of a standard or recommendation, as in
V.27ter.

terabit

A terabit is usually taken to mean one million megabits, or 1,000,000,000,000 (1012) bits.

terabyte

As a unit of memory measurement, a terabyte is usually taken to mean
1,099,511,627,776 (240) bytes.

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29 July 2005

Master Glossary – T

terminal emulation

Software that allows a PC to mimic the signals of a specific type of terminal, such as a
VT100 or 3270, to communicate with a device requiring that terminal interface.

TFTP

Trivial File Transfer Protocol. A standard TCP/IP protocol that allows simple file transfer to
and from a remote system without directory or file listing.

throughput

Amount of data, or the number of data units per units of time, that pass through the network
when it is operating a peak capacity.

TID

Target IDentifier. In TL1, the network entity to which a command is directed.

time slot

One of the ways in which bandwidth can be specified for multiplexer channel groups. Time
slots are specified by any number from one to twenty-four, with each time slot equal to
64 Kbps.

TL1

Transaction Language 1. A language developed by Bellcore (now Telcordia Technologies,
Inc.) as a user interface for telecommunications equipment.

Test Mode. An EIA lead standard for V.24 circuit TM, ITU 142; an output signal
(DCE-to-DTE).

Traffic Management. The actions taken by the ATM layer to deter network congestion.

TMp

Trellis Multipoint. A proprietary high speed, fast poll multipoint modulation scheme.

token ring

A type of network that supports high-speed communications between computers.

tone dialing

A dialing method in which telephone numbers are sent as tones across the telephone lines.

top talkers

Network users generating the most traffic.

TOS

TR 54016

AT&T Technical Reference 54016, Requirements for Interfacing Digital Terminal Equipment
to Services Employing the Extended Superframe Format. An AT&T specification that
defines T1 operation.

TR 62310

AT&T Technical Reference 62310, DS0 Digital Local Channel: Description & Interface
Specification.

TraceRoute

A program that lists the hosts in the path to a specified destination.

traffic descriptor

A generic description consisting of a list of traffic parameters, a cell delay variation
tolerance, and a conformance definition, used to negotiate a connection.

training

A process where two modems try to establish a connection over the telephone (voice
frequency) line.

transceiver

A circuit capable of acting as both a transmitter and a receiver.

transmitter

A circuit capable of generating, modulating, and sending a signal for communication,
control, and other purposes.

trap (SNMP)

A notification message to the SNMP manager when an unusual event occurs on a network
device, such as a reinitialization.

trellis-coded
modulation

Advanced error correction coding technique for primary data typically used on higher speed
modems. This modulation scheme uses Forward Error Correction for multipoint and
high-speed point-to-point applications.

tributary unit

A unit that is under the control of another unit.

Triple Play

A term used to describe a device or system that supports concurrent transmission of data,
voice, and video.

29 July 2005

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Master Glossary – T

TTL

Time To Live. A hop counter in a datagram used to protect a best-effort delivery system
from routing loops.

Transmit. To send signals from a device.

TXC

Transmit Clock. V.24 circuit 114.

TXD

Transmit Data.

GL-60

29 July 2005

Master Glossary – U

U
UAS

Unavailable Seconds. A count of one-second intervals when service is unavailable.

UAWG

Universal ADSL Working Group. An organization consisting of representatives from
Compaq, Intel, Microsoft, RBOCs, and other companies, that is formulating a standard for
the implementation of ADSL.

UBR

Unspecified Bit Rate. An ATM service category with no commitment of bandwidth.

UDP

User Datagram Protocol. A TCP/IP protocol describing how messages reach application
programs within a destination computer.

U-Interface

Marks the demarcation line between the customer-provided equipment and the local
telephone company. Interface provides basic rate access.

Underwriter’s Laboratories, Inc. An organization which promotes product safety.

unassigned cell

An ATM cell that contains a Virtual Path Identifier (VPI) and a Virtual Channel Identifier
(VCI) but no application data.

UNI

User-Network Interface. The interface of an ATM end user and an ATM switch, or an ATM
switch and a public carrier.

UNI

User-to-Network Interface. The interface of frame relay user equipment and a frame relay
network.

unicasting

In ATM, the sending of a Protocol Data Unit (PDU) to a single destination.

UNIX

An operating system developed at AT&T Bell Laboratories and since used as the basis of
similar operating systems.

UPC

Usage Parameter Control. In ATM, the set of actions taken by the network to control traffic.

upload

A file transfer in which you send a file to another computer.

upstream

In the direction of the telephone network.

upstream modem

A device connected logically closer to the host computer.

URL

Uniform Resource Locator. An Internet standard addressing protocol for location and
access of resources.

USB

Universal Serial Bus. A standard for a low-cost external peripheral device interface that
operates at 12 Mbps.

USOC

Universal Service Ordering Codes. Generic telephone company service ordering codes.

UTOPIA

Universal Test and OPerations Interface for ATM. The electrical interface of sublayers of the
ATM physical layer.

UTC

Coordinated Universal Time. An international time used in navigation and networking,
supplanting Greenwich Mean Time. It is also known as Zulu time.

UTP

Unshielded Twisted Pair.

29 July 2005

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Master Glossary – V

V
V.17

An ITU-T fax communications standard for devices operating half-duplex with synchronous
data at 14,400 bps.

V.21

An ITU-T standard for devices operating full-duplex with asynchronous or synchronous data
at 300 bps over dial telephone lines.

V.22

An ITU-T standard for modems operating full-duplex with asynchronous or synchronous
data at 1200 bps over the dial network (PSTN).

V.22bis

An ITU-T standard for modems operating full-duplex with asynchronous or synchronous
data at 1200 or 2400 bps over the dial network (PSTN).

V.23

An ITU-T standard for modems operating full-duplex with asynchronous or synchronous
data at 1200 or 600 bps over dial or leased telephone lines.

V.24

An ITU-T standard for a low-speed, 25-position, DCE/DTE interface.

V.25bis

An ITU-T standard dialing protocol that permits direct and stored-number dialing in
asynchronous, bisynchronous, or HDLC modes.

V.27bis

An ITU-T communications standard for modems operating in synchronous mode at 4800 or
2400 bps.

V.27ter

An ITU-T fax communications standard for modems operating half-duplex with synchronous
data at 2400 and 4800 bps.

V.29

An ITU-T communications standard for modems operating half-duplex with synchronous
data at 7200 and 9600 bps.

V.32

An ITU-T standard for modems operating full-duplex with asynchronous or synchronous
data at 4800 or 9600 bps on switched (dial) or leased telephone lines.

V.32bis

An ITU-T standard for modems operating full-duplex with asynchronous or synchronous
data over dial networks (PSTN) or leased lines at 14,400, 12,000, 9600, 7200, or 4800 bps.

V.32terbo

A modulation that adds the 19,200 bps and 16,800 bps data rates to the V.32bis data rates.
It is a proprietary modulation, not an ITU-T standard.

V.33

An ITU-T standard for devices operating half-duplex with synchronous data at 14,400 and
12,000 bps.

V.34

An ITU-T standard for modems operating full-duplex with asynchronous or synchronous
data over leased lines or dial networks at 33,600, 31,200, 28,800, 26,400, 24,000, 21,600,
19,200, 16,800, 14,400, 12,000, 9600, 7200, 4800, 2400 bps.

V.35

An ITU-T standard for a high-speed, 34-position, DCE/DTE interface.

V.42

An ITU-T standard for error control protocol.

V.42bis

An ITU-T standard for data compression.

V.42t

A proprietary Synchronous Data Compression and error correction technique.

V.54

An ITU-T standard for local and remote diagnostic loopback tests.

V.54 Loop 2

An ITU-T standard for a data channel loopback (DCLB).

V.54 Loop 3

An ITU-T standard for a data terminal loopback (DTLB).

variable binding

The pairing of the name of a variable with a stored value. A list of variable bindings is used
in SNMP Get and Set requests.

GL-62

29 July 2005

Master Glossary – V

VBR

Variable Bit Rate. An ATM service category that supports average and peak traffic rate
parameters.

Virtual Circuit. A logical connection or packet-switching mechanism established between
two devices at the start of transmission.

VCC

Virtual Channel Connection. A concatenation of Virtual Circuit Links (VCLs) that joins users
of the ATM layer.

VCI

Virtual Channel Identifier. The 16-bit field in an ATM cell header that specifies the virtual
channel over which the cell is to be transmitted.

VCID

Virtual Circuit IDentifier. A non-unique local endpoint circuit identifier used by a switch to
look up a path for data packets presented to it.

VDSL

Very-high-speed DSL. A developing recommendation for a DSL protocol running at up to
52 Mbps over short distances.

Voice Frequency. The part of the audio frequency range used to transmit voice sound
(usually 300 Hz to 3400 Hz). This band is used by the modem for its modulated signal.

VF Impairments

A type of voice frequency line distortion, such as receive level or frequency offset.

VF Threshold

Voice Frequency Threshold. The set of programmable parameters used to define
acceptable ranges (thresholds) of voice frequency channel characteristics. An alarm
generates when a measured voice frequency channel characteristic is outside the
acceptable range defined by the threshold(s).

VF Threshold Alarm

A notification that a measured voice frequency channel characteristic is outside the
acceptable range defined by the threshold(s).

VGA

Video Graphics Adapter.

virtual circuit

A logical link/connection or packet-switching mechanism established between two devices
at the start of transmission.

VLAN

Virtual Local Area Network. A logical grouping of users regardless of their physical location
on a network.

VLAN switch

A layer 2 networking device used for implementing a VLAN.

VNID

Virtual Network IDentifier. In IEEE 802.1Q, a tag that identifies the connection between the
user and the ISP.

VOD

Video On Demand. A service that provides video to subscribers upon request.

VoDSL

Voice over DSL.

volatile

A term used to describe memory which loses its contents when the device is powered
down.

VPC

Virtual Path Connection. In ATM, a unidirectional concatenation of Virtual Path Links (VPLs)
between Virtual Path Terminators (VPTs).

VPI

Virtual Path Identifier. The 8-bit field in an ATM cell header that specifies the virtual path
over which the cell should be routed.

VPL

Virtual Path Link. The medium between the point where a Virtual Path Identifier (VPI) is set
and the point where it is interpreted or removed.

VPN

Virtual Private Network. A network implemented over a public network and rendered private
by use of encryption.

VPT

Virtual Path Terminator. In ATM, the system that separates for processing the individual
Virtual Circuits (VCs) of a Virtual Path Connection (VPC).

29 July 2005

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Master Glossary – V

VSAT

Very Small Aperture Terminal. A ground station for satellite-based telecommunications.

VT100

A Digital Equipment Corporation terminal, and a common terminal emulation mode used for
asynchronous communications.

GL-64

29 July 2005

Master Glossary – W

W
W3C

World Wide Web Consortium. The international organization that develops standards for the
World Wide Web.

WAN

Wide Area Network. A network that spans a large geographic area.

WAN-C

Wide Area Network Concentrator. A router or VLAN switch that concentrates data traffic
onto facilities providing access to the WAN.

WFQ

Weighted Fair Queueing. A congestion management algorithm in which a traffic class is
assigned a relative amount of bandwidth.

wink start

A supervisory signaling technique in which the CPE signals the CO that it is off-hook by
sending a momentary pulse to the CO.

winkback detection

In telephone switching systems, a momentary signal state change from control mode idle
(CMI) to data mode idle (DMI), and back to CMI (sometimes referred to as a wink start).

WIPO

World Intellectual Property Organization. An international organization dedicated to the
protection of intellectual property.

wire center

A point of access to the physical wires of a telecommunications network.

word

In microcomputers, two contiguous bytes treated as a datum, usually beginning at an
address evenly divisible by two.

workstation

A user terminal.

X, Y, Z
X.21

An ITU-T standard for a high-speed, 15-position, DCE/DTE interface.

xDSL

A generic term for all varieties of DSL taken as a whole.

XML

EXtensible Markup Language. A simplified dialect of SGML proposed by the W3C for use
on the World Wide Web.

XOFF

A character that tells the DTE or modem to stop transmitting data.

XON

A character that tells the DTE or modem to start or resume transmitting data.

XSL

EXtensible Stylesheet Language. A language used for formatting XML documents.

XSLT

XSL Transformations. A language for describing how one XML document is transformed
into another.

XTACACS

EXtended Terminal Access Controller Access Control System. A user authentication
protocol, it is a Cisco extension of RFC 927.

XTXC

External Transmit Clock. V.24 circuit 113.

Yellow Alarm

An outgoing signal transmitted when a DS1 or DS3 terminal has determined that it has lost
the incoming signal.

29 July 2005

GL-65

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