| Word
/Term/Acronym |
Definition |
| 100BaseT |
A
100-Mbps local area network that maintains backward
compatibility with 10BaseT networks running at 10 Mbps. |
| 10BaseT |
A
10-Mpbs Ethernet local area network that runs over
twisted pair wiring. This network interface was
originally designed to run over ordinary twisted pair
(phone wiring) but is predominantly used with Category 3
or 5 cabling |
| 5ESS |
A
digital central-office switching system made by
AT&T. It is typically used as an
"end-office," serving local subscribers. |
| Access
Network |
That
portion of a public switched network that connects
access nodes to individual subscribers. The Access
Network today is predominantly passive twisted pair
copper wiring. |
| Access
Nodes |
Points
on the edge of the Access Network that concentrate
individual access lines into a smaller number of feeder
lines. Access Nodes may also perform various forms of
protocol conversion. Typical Access Nodes are Digital
Loop Carrier systems concentrating individual voice
lines to T1 lines, cellular antenna sites, PBXs, and
Optical Network Units. |
| Adapter
Card |
An electronics
board installed in a PC, which provides a network
interface to and from that computer. Also called a
network interface card (NIC). |
| ADSL |
Asymmetric
Digital Subscriber Line. An xDSL technology providing
asymmetrical bandwidth over a single wire pair. The
downstream bandwidth going from the network to the
subscriber is typically greater than the upstream
bandwidth going from the subscriber to the network. |
| ADSL
Termination Unit - Central Office |
(ATU-C)
The device at the end of an ADSL line that stands
between the line and the first item of equipment in the
telephone switch. It may be integrated within an access
node. |
| ADSL
Termination Unit - Remote |
(ATU-R)
The device at the end of an ADSL line that stands
between the line and the first item of equipment in the
subscriber's premises. It may be integrated within an
access node. |
| Aerial
Cable |
Telecommunications
cable that is attached to poles. |
| American
National Standards Institution |
(ANSI) A
private (nonprofit membership) organization, founded in
1918, which develops and publishes standards for
voluntary use in the United States. It is chartered to
define, evaluate, and promote industrial standards for
product compatibility. ANSI created ASCII, or American
Standard Code for Information Interchange. |
| American
Wire Gauge |
(AWG)
A measure of the thickness of copper, aluminum and other
wiring in the U.S. and elsewhere. Copper cabling
typically varies from 18 to 26 AWG. The higher the
number, the thinner the wire. The thicker the wire, the
less suceptible it is to interference. In general, thin
wire cannot carry the same amount of electrical current
the same distance that thicker wire can. |
| Analog |
A signal that
varies continuously over time (for example, as in sound
waves). Analog signals are described in terms of
frequency (Hz, cycles per second), amplitude, and phase
relationship. All DSL signals are modulated from digital
signals at the modem to analog signals on the telephone
lines. |
| ANSI |
American
National Standards Institution. A private (nonprofit
membership) organization, founded in 1918, which
develops and publishes standards for voluntary use in
the United States. It is chartered to define, evaluate,
and promote industrial standards for product
compatibility. ANSI created ASCII, or American Standard
Code for Information Interchange. |
| Asymmetric
Digital Subscriber Line |
(ADSL)
An xDSL technology providing asymmetrical bandwidth over
a single wire pair. The downstream bandwidth going from
the network to the subscriber is typically greater than
the upstream bandwidth going from the subscriber to the
network. |
| Asymmetric
digital subscriber line Termination Unit Central office |
(ATU-C) The
device at the end of an ADSL line that stands between
the line and the first item of equipment in the
telephone switch. It may be integrated within an access
node. |
| Asymmetric
digital subscriber line Termination Unit Remote |
(ATU-C)
The device at the end of an ADSL line that stands
between the line and the first item of equipment in the
subscriber's premises. It may be integrated within an
access node. |
| Asymmetrical |
Transmission
where the downstream bit rate and the upstream bit rate
differ. |
| Asynchronous
Transfer Mode |
(ATM)
An internationally standardized implementation of cell
relay technology, ATM represents the first worldwide
standard to be embraced by the computer, communications,
and entertainment industry. ATM is a high-bandwidth,
low-delay, connection-oriented, packet-like switching
and multiplexing technique for data transmission that
communicates all types of information (traditionally
data, burst data, voice, video, image, and cell) over a
common backbone using fixed cell lengths. ATM uses a
53-byte cell format that includes a 5-byte header and 48
bytes of payload. |
| ATM |
Asynchronous
Transfer Mode. An internationally standardized
implementation of cell relay technology, ATM represents
the first worldwide standard to be embraced by the
computer, communications, and entertainment industry.
ATM is a high-bandwidth, low-delay, connection-oriented,
packet-like switching and multiplexing technique for
data transmission that communicates all types of
information (traditionally data, burst data, voice,
video, image, and cell) over a common backbone using
fixed cell lengths. ATM uses a 53-byte cell format that
includes a 5-byte header and 48 bytes of payload. |
| ATM
Backbone |
Uses
technology based on transferring data in packets of a
fixed size. By packetizing traffic into cells and
providing very fast switches, it allows video, audio and
computer data to be transmitted over the same network,
and assures that no single type of data saturates the
line. The ATM backbone is the equipment that provides
high-speed connectivity for users. |
| Attenuate |
The decrease
in power of a signal across any communications transport
medium. Also known as loss (opposite of gain); measured
in decibels (dB). |
| ATU-C |
ADSL
Termination Unit - Central Office. The device at the end
of an ADSL line that stands between the line and the
first item of equipment in the telephone switch. It may
be integrated within an access node. |
| ATU-C |
Asymmetric
digital subscriber line Termination Unit Central office.
The device at the end of an ADSL line that stands
between the line and the first item of equipment in the
telephone switch. It may be integrated within an access
node. |
| ATU-R |
ADSL
Termination Unit - Remote. The device at the end of an
ADSL line that stands between the line and the first
item of equipment in the subscriber's premises. It may
be integrated within an access node. |
| ATU-R |
Asymmetric
digital subscriber line Termination Unit Remote. The
device at the end of an ADSL line that stands between
the line and the first item of equipment in the
subscriber's premises. It may be integrated within an
access node. |
| AWG |
American
Wire Gauge. A measure of the thickness of copper,
aluminum and other wiring in the U.S. and elsewhere.
Copper cabling typically varies from 18 to 26 AWG. The
higher the number, the thinner the wire. The thicker the
wire, the less suceptible it is to interference. In
general, thin wire cannot carry the same amount of
electrical current the same distance that thicker wire
can. |
| B
Channel |
Bearer
Channel. A communications channel. It is usually in an
Integrated Services Digital Network (ISDN) system, but
possibly in any system that carries user (as opposed to
system) data at the standard DS0 data rate of 64 kbps. |
| Backbone |
Equipment
that provides connectivity for users of distributed
network and includes all the network infrastructure
required to provide connectivity between the edge
vehicles. In the context of the Internet, this terms
also refers high-volume, "primary" data
carriers that make-up the long-haul capabilities of the
network. |
| Band |
A range of
frequencies from a lower limit to an upper limit. For
example, the voice frequency (VF) band is the range from
300 to 3400 Hz. |
| Bandpass
Filter |
A device that
passes or transmits a given band of frequencies and
blocks all other frequencies. In asymmetric digital
subscriber line (ADSL), the voice frequency band of 300
Hz is blocked and redirected to a telephone set and all
other frequencies are passed through to the modem or
transceiver. The plain old telephone service (POTS)
splitter is essentially a combination low-pass and
high-pass filter; <10 kHz frequencies go to the phone
service, and 15 kHz> f >1 MHz frequencies to ADSL
(carrierless amplitude phase [CAP] and discrete
multitone [DMT]). |
| Bandwidth |
The amount of
information or data that can be sent over the Internet
in a given period of time. Bandwidth is usually stated
in bits per second (bps), kilobits per second (Kbps) or
megabits per second (Mbps). |
| Bandwidth |
The frequency
range that a device or medium will pass or respond to.
It is computed by subtracting the lower frequency limit
from the upper frequency limit and is expressed in hertz
(Hz). For example, the typical telephone circuit
responds to all frequencies between 300 and 3400 Hz;
therefore, its bandwidth is 3100 Hz. In informal common
usage in digital communications, bandwidth is used to
indicate the maximum transmission rate of a facility in
bits per second (for example, 4800 bps), or the
information carrying capacity of a medium or system. In
E1/2M, cycles per second (CPS) is still commonly used in
lieu of hertz. |
| Basic
Rate Interface |
(BRI) In an
ISDN, the BRI is a two-wire interface between the
customer premises equipment (CPE) and the telco end
office (EO), and a four-wire interface at the customer
premises. BRI service provides two clear 64-kbps (B)
channels for voice or data and one 16-kbps (D) channel
for signaling information or data. BRI service is
primarily for home or small business use.B161 |
| Basic
Rate Interface |
(BRI) This is
an Integrated Services Digital Network (ISDN) interface
typically used by smaller sites and customers. This
interface consists of a single 16 Kbps Data (or
"D") channel plus 2 Bearer (or "B")
channels for voice and/or data. Also known as Basic Rate
Access, or BRA. |
| BDSL |
Broadband
Digital Subscriber Line. Same as VDSL. |
| Bearer
Channel |
(B
Channel) A communications channel. It is usually in an
Integrated Services Digital Network (ISDN) system, but
possibly in any system that carries user (as opposed to
system) data at the standard DS0 data rate of 64 kbps. |
| BER |
Bit
Error Rate. Represents the ratio of the number of erred
bits to the total number of hits delivered in a digital
system. BERs of less than one in one billion are not
uncommon in today's digital communication systems. |
| BERT |
Bit
Error Rate Test. A test that reflects the ratio of
errored bits to the total number transmitted. Usually
shown in exponential form (10^-6) to indicate that one
out of a certain number of bits are in error. |
| Binary
Digit |
(Bit) A bit is
the smallest unit of data that can be processed by a
computer; expressed as the presence or absence of a
pulse to represent a binary 1 or 0. |
| Bit |
Binary Digit.
A bit is the smallest unit of data that can be processed
by a computer; expressed as the presence or absence of a
pulse to represent a binary 1 or 0. |
| Bit
Error |
When the value
of a bit has been changed during transmission and is
incorrectly received. |
| Bit
Error Rate |
(BER)
Represents the ratio of the number of erred bits to the
total number of hits delivered in a digital system. BERs
of less than one in one billion are not uncommon in
today's digital communication systems. |
| Bit
Error Rate Test |
(BERT)
A test that reflects the ratio of errored bits to the
total number transmitted. Usually shown in exponential
form (10^-6) to indicate that one out of a certain
number of bits are in error. |
| Bit
Rate |
The
transmission speed of bits, usually expressed as bits
per second. |
| Bits
Per Second |
(bps) A
measurement of transmission speed |
| Bonding |
Often referred
to as dial-in channel aggregation, takes place at the
customer premises through inverse multiplexing.
Multiplexing takes a high-bandwidth signal and splits it
for transport through the network over multiple
lower-bandwidth channels. At the receiving end, the
multiple lower-bandwidth signals are recombined into the
original high-bandwidth signal. The industry-accepted
standards for inverse multiplexing ISDN connections are
defined by the Bandwidth On Demand Interoperability
Group (BONDING) Consortium and are listed in TIA/EIA 961
and ISO 13871. |
| bps |
Bits Per
Second. A measurement of transmission speed |
| BRI |
Basic Rate
Interface. In an ISDN, the BRI is a two-wire interface
between the customer premises equipment (CPE) and the
telco end office (EO), and a four-wire interface at the
customer premises. BRI service provides two clear
64-kbps (B) channels for voice or data and one 16-kbps
(D) channel for signaling information or data. BRI
service is primarily for home or small business use. |
| BRI |
Basic Rate
Interface. This is an Integrated Services Digital
Network (ISDN) interface typically used by smaller sites
and customers. This interface consists of a single 16
Kbps Data (or "D") channel plus 2 Bearer (or
"B") channels for voice and/or data. Also
known as Basic Rate Access, or BRA. |
| Bridge
Tap |
Any
segment of cable not on a direct path between a central
office (CO) and a subscriber. Also referred to as
bridged tap. |
| Broadband |
A
type of transmission that shares the bandwidth of a
medium--such as copper or fiber optic cable--to carry
more than one signal. Broadband facilities have a
bandwidth (capacity) greater than a voice grade line of
3 kHz. Such a broadband facility--typically coaxial
cable--may carry numerous voice, video and data channels
simultaneously. Each "channel" will take up a
different frequency on the cable. "Guardbands"
(empty spaces) exist between the channels to make sure
that each channel does not interfere with its neighbor.
A coaxial CATV cable is the "classic"
broadband channel. Simultaneously it carries many TV
channels. Broadband cables are used in some office LANs.
But more common are the baseband variety, which have the
capacity for one channel only. Everything on that cable
to be transmitted or received must use that one channel.
That one channel is very fast, so each device needs only
to use that high speed channel for only a little of the
time. (The problem is getting on the channel.) See also
baseband. |
| Broadband
Digital Subscriber Line |
(BDSL)
Same as VDSL. |
| Broadband
Integrated Services Digital Network |
(BISDN)
A digital network with ATM switching operating at data
rates in excess of 1.544 or 2.048 Mbps. ATM enable
transport and switching of voice, data, image, and video
over the same infrastructure. |
| Cable |
A group of
conductors (metallic pairs, coaxial, optical fibers)
assembled within a common, protective sheath. |
| Call
Setup |
The process of
establishing a connection between two communicating
entities. In the voice network, call setup involves
interpreting the dialed number and establishing a
connection between the caller and the destination. The
process is similar for data calls, but usually requires
more negotiation of parameters. |
| Call
Teardown |
The procedure
of disconnecting a call between the CO and the
subscriber. |
| CBR |
Constant Bit
Rate |
| CCITT |
Consultative
Committee for International Telegraph and Telephone |
| Central
Office |
(CO)
A circuit switch that terminates all the local access
lines in a particular geographic serving area; a
physical building where the local switching equipment is
found. xDSL lines running from a subscriber’s home
connect at their serving central office. |
| Channel |
The smallest
subdivision of a communication path on a digital,
multiplexed signal for which information can be provided
in one direction. |
| Channel
Service Unit |
CSU |
| Channelized |
A transmission
option for subscribers of symmetrical services.
Channelized service allows a subscriber to assign one
device (such as a PC) to a DS0 channel, resulting in
many devices being able to transmit and receive
simultaneously at 64 kbps. |
| Chipset |
A
configuration of two or more microchips for the purpose
of a specific function. |
| CIR |
Committed
Information Rate |
| Class
Of Service |
(COS)
Method of classifying different traffic flows into a
category and applying a particular quality of service (QoS)
for that flow. |
| CLEC |
Competitive
Local Exchange Carrier. A competitor to (ILEC) Incumbent
Local Exchange Carrier (your local phone company)
offering telecommunications service. |
| CO |
Central
Office. A circuit switch that terminates all the local
access lines in a particular geographic serving area; a
physical building where the local switching equipment is
found. xDSL lines running from a subscriber’s home
connect at their serving central office. |
| Coaxial
Cable |
Is
characterized by a solid or stranded center conductor
surrounded by a dielectric layer (insulator), which in
turn is surrounded by foil, braid, or both types of
metallic ground conductors or shields. In most
applications, there is an outer plastic jacket to
protect the shield. The conductor and the outer layers
are all on a common axis. The most commonly recognized
application of coaxial cable is its use for cable
television delivery. |
| CODEC |
An
abbreviation for coder/decoder. Specifically it converts
a voice grade analog signal to u-law or A-law encoded
samples at an 8KHz sampling rate. DSL bypasses the
CODECs at the central office by separating the
frequencies in a POTS splitter and passing the DSL
signal to a DSLAM, the DSL equivalent of a CODEC. |
| Coder
/ Decoder |
(CODEC)
An abbreviation for coder/decoder. Specifically it
converts a voice grade analog signal to u-law or A-law
encoded samples at an 8KHz sampling rate. DSL bypasses
the CODECs at the central office by separating the
frequencies in a POTS splitter and passing the DSL
signal to a DSLAM, the DSL equivalent of a CODEC. |
| Committed
Information Rate |
CIR |
| Competitive
Local Exchange Carrier |
(CLEC)
A competitor to (ILEC) Incumbent Local Exchange Carrier
(your local phone company) offering telecommunications
service. |
| Constant
Bit Rate |
CBR |
| Consultative
Committee for International Telegraph and Telephone |
CCITT |
| Core
Network |
Combination
of switching offices and transmission plant connecting
switching offices together. In the U.S. local exchange
Core Networks are linked by several competing
Interexchange networks; in the rest of the world (now)
the Core Network extends to national boundaries. CSA
Carrier Serving Area. |
| COS |
Class
Of Service. Method of classifying different traffic
flows into a category and applying a particular quality
of service (QoS) for that flow. |
| CPE |
Customer
Premise (or Provided) Equipment. Customer owned
communications equipment that resides on the customer's
premises. The CPE for DSL services is a DSL modem. |
| CSU |
Channel
Service Unit. |
| Customer
Premise (or Provided) Equipment |
(CPE)
Customer owned communications equipment that resides on
the customer's premises. The CPE for DSL services is a
DSL modem. |
| D
Channel |
In an ISDN
interface, the D channel is used to carry control
signals and customer call data in a packet-switched
mode. In the ISDN Basic Rate Interface (BRI), the D
channel operates at 16 kbps, and in the ISDN Primary
Rate Interface (PRI), the D channel operates at 64 kbps. |
| Data
Communication (or Circuit-Terminating) Equipment |
DCE |
| Data
Link Connection Identifier |
(DLCI
) The Frame Relay virtual circuit number used in
internetworking to denote the port to which the
destination LAN is attached. |
| Data
Service Unit |
(DSU) A
digital interface device that connects end user data
communications equipment to the digital access lines,
and which provides framing of sub-64Kbps customer access
channels onto higher rate data circuits. A DSU may be
combined with a CSU into a single device called a CSU/DSU.
See Channel Service Unit/Data Service Unit. |
| Data
Service Unit/Channel Service Unit |
(DSU/CSU)
The devices used to access digital data channels are
called DSU/CSUs (Data Service Unit/Channel Service
Units). At the customer's end of the telephone
connection, these devices perform much the same function
for digital circuits that modems provide for analog
connections. For example, DSU/CSUs take data from
terminals and computers, encode it, and transmit it down
the link. At the receive end, another DSU/CSU equalizes
the received signal, filters it, and decodes it for
interpretation by the end-user. |
| Data
Terminal (or Termination) Equipment |
(DTE)
Typically the device that transmits data such as a
personal computer or data terminal. |
| dB |
Decibel. The
unit of measure for signal loss or gain. It is used to
express the ratio of two powers, voltages, currents, or
sound intensities. |
| DCE |
Data
Communication (or Circuit-Terminating) Equipment |
| DDS |
Digital
Data Service. Private line digital service with data
rates of 56/64 kbps. |
| Decibel |
(dB) The unit
of measure for signal loss or gain. It is used to
express the ratio of two powers, voltages, currents, or
sound intensities. |
| Dedicated
Line |
A
transmission circuit that is reserved by the provider
for the full-time use of the subscriber. Also called a
"private line." |
| Demarcation |
The point
between the wiring that comes in from your local
telephone company and the wiring you install to hook up
your telephone system to the point where the telco's
responsibility to maintain or replace lines or equipment
ends and a subscriber's begins. Usually a network
interface device (NID) is the demarcation point. |
| Demultiplex |
Reversing the
process of multiplexing; the separation of the
individual channels from the multiplexed signal. |
| Demux |
A demux, or
demultiplexer, accepts a large bandwidth signal
comprising numerous channels of information and
separates it into distinct, individual signals.
Demultiplexing is the opposite action of multiplexing. |
| DHCP |
Dynamic Host
Configuration Protocol. Enables individual computers on
an IP network to extract their configuration from a DHCP
server or servers, in particular, servers that have no
exact information about the individual computers until
they request the information. The overall purpose is to
reduce the work necessary to administer a large IP
network. |
| Dial
Up |
The
process of initiating a switched connection through the
network; when used as an adjective, this is a type of
communication that is established by a switched-circuit
connection. |
| Digital |
An electrical
or electronic signal made up of discontinuous pulses,
whose information is contained in their durations,
periods, or amplitudes. A digital signal varies
discretely over time and uses only two signal states or
conditions to represent information. Binary states of
1.0, high/low, and on/off are examples of digital signal
states that can be used to represent information. |
| Digital
Data Service |
(DDS)
Private line digital service with data rates of 56/64
kbps. |
| Digital
Signal Level |
(DS
0-4) Standard digital transmission rates used in North
America. Digital signal level zero (DS0) represents the
64-kbps single-channel signal generated by a T1 terminal
device such as a channel bank, multiplexer (MUX), or
digital PBX. Each level supports a different number of
digital voice-channels.
• DS0 is equivalent to 1 digital voice channel and has
a line rate 64 kbps.
• DS1 (or T1) supports 24 digital voice channels and a
line rate of 1.544 Mbps.
• DS1C (or T1C) supports 48 digital voice channels and
a line rate of 3.152 Mbps.
• DS2 (or T2) supports 4 DS1s (96 digital voice
channels) and a line rate of 6.132 Mbps.
• DS3 (or T3) supports 28 DS1s (7 DS2s, 672 digital
voice channels) and a line rate of 44.736 Mbps.
• DS4 (or T4) supports 168 DS1s (6 DS3s, 42 DS2s, 4032
digital voice channels and a line rate of 274.176 Mbps. |
| Digital
Signal Processor |
(DSP) A
specialized, programmable computer chip designed to
perform speedy and complex operations on digitized
waveforms. A DSP-based modem uses a DSP for analog and
digital modem communications. The DSP-based modem is
programmable for easy upgrades. |
| Digital
Subscriber Line |
(DSL)
Another term denoting xDSL. A family of technologies
transmitting digital information (and sometimes POTS)
over existing copper wire pairs for limited distances.
The "x" in xDSL stands for any number of
letters denoting the xDSL family members, commonly IDSL,
SDSL, HDSL, ADSL, and VDSL. |
| Digital
Subscriber Line Access Multiplexer |
(DSLAM)
A device that concentrates traffic in DSL
implementations through a process of time-division
multiplexing (TDM) at the CO or remote line shelf. This
device is usually located in the CO for termination of
multiple customer DSL devices. |
| Discrete
Multi Tone |
(DMT)
A line code used in some transceivers or modems to
transport digital signals. DMT employs rate adaptation
and is used in the ANSI standard for xDSL technologies.
Currently, ANSI T1.413 Issue 2, International
Telecommunications Union (ITU) 992.1 (G.dmt), and ITU
992.2 (G.lite) use DMT as their core modulation scheme. |
| DLCI |
Data
Link Connection Identifier. The Frame Relay virtual
circuit number used in internetworking to denote the
port to which the destination LAN is attached. |
| DMT |
Discrete
Multi Tone. A line code used in some transceivers or
modems to transport digital signals. DMT employs rate
adaptation and is used in the ANSI standard for xDSL
technologies. Currently, ANSI T1.413 Issue 2,
International Telecommunications Union (ITU) 992.1 (G.dmt),
and ITU 992.2 (G.lite) use DMT as their core modulation
scheme. |
| DNS |
Domain
Name Services. The collection of protocols and methods
for mapping human-friendly domain names (e.g.,
select.net) to machine-friendly IP addresses (e.g.,
127.192.11.34) for the purposes of accessing Internet
services. |
| DNS
Registration |
Domain
Name Services Registration |
| Domain
Name Services |
(DNS)
The collection of protocols and methods for mapping
human-friendly domain names (e.g., select.net) to
machine-friendly IP addresses (e.g., 127.192.11.34) for
the purposes of accessing Internet services. |
| Domain
Name Services Registration |
DNS
Registration |
| Downloading |
Sending a copy
of a file containing a program or data from a central
storage device (for example, LAN file server) to a PC
where it will be stored locally on auxiliary storage. |
| Downstream |
Refers
to transmission speed from the CO to the service user. |
| Downstream
Transmission |
A
telecommunications transmission travelling from the
telco CO to the subscriber's location. |
| DS
0-4 |
Digital
Signal Level. Standard digital transmission rates used
in North America. Digital signal level zero (DS0)
represents the 64-kbps single-channel signal generated
by a T1 terminal device such as a channel bank,
multiplexer (MUX), or digital PBX. Each level supports a
different number of digital voice-channels.
• DS0 is equivalent to 1 digital voice channel and has
a line rate 64 kbps.
• DS1 (or T1) supports 24 digital voice channels and a
line rate of 1.544 Mbps.
• DS1C (or T1C) supports 48 digital voice channels and
a line rate of 3.152 Mbps.
• DS2 (or T2) supports 4 DS1s (96 digital voice
channels) and a line rate of 6.132 Mbps.
• DS3 (or T3) supports 28 DS1s (7 DS2s, 672 digital
voice channels) and a line rate of 44.736 Mbps.
• DS4 (or T4) supports 168 DS1s (6 DS3s, 42 DS2s, 4032
digital voice channels and a line rate of 274.176 Mbps. |
| DSL |
Digital
Subscriber Line. Another term denoting xDSL. A family of
technologies transmitting digital information (and
sometimes POTS) over existing copper wire pairs for
limited distances. The "x" in xDSL stands for
any number of letters denoting the xDSL family members,
commonly IDSL, SDSL, HDSL, ADSL, and VDSL. |
| DSLAM |
Digital
Subscriber Line Access Multiplexer. A device that
concentrates traffic in DSL implementations through a
process of time-division multiplexing (TDM) at the CO or
remote line shelf. This device is usually located in the
CO for termination of multiple customer DSL devices. |
| DSP |
Digital Signal
Processor. A specialized, programmable computer chip
designed to perform speedy and complex operations on
digitized waveforms. A DSP-based modem uses a DSP for
analog and digital modem communications. The DSP-based
modem is programmable for easy upgrades. |
| DSU |
Data Service
Unit. A digital interface device that connects end user
data communications equipment to the digital access
lines, and which provides framing of sub-64Kbps customer
access channels onto higher rate data circuits. A DSU
may be combined with a CSU into a single device called a
CSU/DSU. See Channel Service Unit/Data Service Unit. |
| DSU/CSU |
Data
Service Unit/Channel Service Unit.
The devices used to access digital data channels
are called DSU/CSUs (Data Service Unit/Channel Service
Units). At the customer's end of the telephone
connection, these devices perform much the same function
for digital circuits that modems provide for analog
connections. For example, DSU/CSUs take data from
terminals and computers, encode it, and transmit it down
the link. At the receive end, another DSU/CSU equalizes
the received signal, filters it, and decodes it for
interpretation by the end-user. |
| DTE |
Data Terminal
(or Termination) Equipment. Typically the device that
transmits data such as a personal computer or data
terminal. |
| DTMF |
Dual Tone
Multi-Frequency. A method for touch-tone phones
developed to make dialing an easier process; each digit
corresponds to one of 16 combinations of pairs of sine
waves chosen from eight different frequencies (example:
the 7 digit is defined as the combination of 852 Hz and
1209 Hz) |
| Dual
Tone Multi-Frequency |
(DTMF) A
method for touch-tone phones developed to make dialing
an easier process; each digit corresponds to one of 16
combinations of pairs of sine waves chosen from eight
different frequencies (example: the 7 digit is defined
as the combination of 852 Hz and 1209 Hz) |
| Duplex |
A
characteristic of data transmission, either full-duplex
or half-duplex. Full-duplex transmission permits
simultaneous, two-way communication. Half-duplex
transmission means only one side can transmit at a time. |
| Dynamic
Host Configuration Protocol |
(DHCP) Enables
individual computers on an IP network to extract their
configuration from a DHCP server or servers, in
particular, servers that have no exact information about
the individual computers until they request the
information. The overall purpose is to reduce the work
necessary to administer a large IP network. |
| E1 |
European
basic multiplex rate which packs thirty voice channels
into a 256 bit frame and transmitted at 2.048 Mbps. |
| ELEC |
Enterprise
Local Exchange Carrier. Generally, a larger corporation
or organization (e.g., university) that operates as its
own local exchange carrier (LEC) as a means of obtaining
better carrier rates for itself, possibly selling
services to others for a profit. ELECs could be
considered a subset of CLECs. See also LEC, ILEC, and
ELEC. |
| Electronic
Mail |
(E-mail) A
method of communicating electronically that allows the
sender to send information to one or more recipients, to
forward electronic correspondence, and to attach other
text and binary files for transmission. E-mail is the
most common application on the Internet. |
| E-mail |
Electronic
Mail. A method of communicating electronically that
allows the sender to send information to one or more
recipients, to forward electronic correspondence, and to
attach other text and binary files for transmission.
E-mail is the most common application on the Internet. |
| Enterprise
Local Exchange Carrier |
(ELEC)
Generally, a larger corporation or organization (e.g.,
university) that operates as its own local exchange
carrier (LEC) as a means of obtaining better carrier
rates for itself, possibly selling services to others
for a profit. ELECs could be considered a subset of
CLECs. See also LEC, ILEC, and ELEC. |
| Enterprise
Network |
A
term for a widely dispersed, multifaceted
telecommunications network for a particular purpose or
organization; a term for all of an organization's
telecommunications networking services and equipment. |
| Ethernet |
One
of the most popular baseband LANs in widespread use. It
is a carrier service multiple access collision detect (CSMA/CD)
system and is usable across a variety of media types. |
| ETSI |
European
Telecommunications Standards Institute. Organization
created by the European post, telephone, and telegraphs
(PTTs) and the European community (EC) to propose
telecommunications standards for Europe. ETSI's task is
to pave the way for telecommunications integration in
the EC as part of the single European market program. |
| European
Telecommunications Standards Institute |
(ETSI)
Organization created by the European post, telephone,
and telegraphs (PTTs) and the European community (EC) to
propose telecommunications standards for Europe. ETSI's
task is to pave the way for telecommunications
integration in the EC as part of the single European
market program. |
| Extended
Definition TV |
(EDTV) A type
of television transmission that offer better picture
resolution than regular TV. This is a generic term
referring to the next generation of broadcast
television. For example, EDTV provides approximately
twice the resolution of today's national television
standard committee (NTSC) and may require from 90 to 900
Mbps for uncompressed transmission. |
| Fast
Ethernet |
A
LAN used to connect devices within a single building or
campus at speeds up to 100 Mbps. Within the OSI model,
Fast Ethernet is defined at layer one (physical) and
layer two (data link). Like Ethernet, Fast Ethernet uses
CSMA/CD. |
| FCC |
Federal
Communications Commission. The United States federal
regulatory agency responsible for regulating interstate,
Inter-LATA, and international communications. |
| FDDI |
Fiber
Distributed Data Interface. A LAN Token Ring standard
using fiber optic cable. |
| FDM |
Frequency-Division
Multiplexing. Consists of separate channels that are
assigned to individual frequencies across the frequency
bandwidth on a common transmission facility. ADSL
technology, for example, has a frequency range of 30 kHz
to 1.1 MHz that can be divided into two nonoverlapping
areas used for upstream and downstream transmission. |
| Federal
Communications Commission |
(FCC)
The United States federal regulatory agency responsible
for regulating interstate, Inter-LATA, and international
communications. |
| Feeder
Network |
That part of a
public switched network which connects access nodes to
the core network |
| Fiber
Distributed Data Interface |
(FDDI)
A LAN Token Ring standard using fiber optic cable. |
| Fiber
To The Curb |
(FTTC) Network
where an optical fiber runs from the telephone switch to
a curbside distribution point close to the subscriber
where it is converted to copper pair. |
| Fiber
To The Home |
(FTTH) Network
where an optical fiber runs from the telephone switch to
the subscriber's premises. |
| Fiber
Optic |
The branch of
optical technology concerned with the transmission of
radiant energy through fibers made of transparent
materials. In telecommunications, fiber-optics are
bundles of thin glass filaments through which light
beams are transmitted, carrying up to 30,000 times the
information of electric waves over copper wire.
Fiber-optics offer low power and space requirements,
with high bandwidth and little sensitivity to
electromagnetic interference. |
| File
Transfer |
A symmetrical
service where a subscriber sends or receives data,
graphics, or video files to or from another subscriber,
usually via the Internet. File transfer is a good
example of a service requiring symmetrical transmission,
because a subscriber may transmit or receive at equally
high bit rates. |
| File
Transfer Protocol |
(FTP)
Internet tool for sending and/or receiving files from a
server linked to the Internet. |
| Firewall |
A
computer device and/or software that separates a Local
Area Network from a Wide Area Network and prevents
unauthorized access to the Local Area Network through
the use of electronic security mechanisms such as IP
filtering, address remapping, etc. |
| Firm
Order Commitment |
FOC |
| FOC |
Firm
Order Commitment |
| FR |
Frame
Relay. A high-speed packet-switched data communications
service, similar to X.25. Frame relay is a leading
contender for LAN-to-LAN interconnect services, and is
well suited to the bursty demands of LAN environments.
See also permanent virtual circuit and switched virtual
circuit. |
| Frame
Relay |
(FR)
A high-speed packet-switched data communications
service, similar to X.25. Frame relay is a leading
contender for LAN-to-LAN interconnect services, and is
well suited to the bursty demands of LAN environments.
See also permanent virtual circuit and switched virtual
circuit. |
| Frame
Relay Forum |
(FRF)
An industry organization whose focus is frame relay
technology. |
| Framing |
A method of
grouping bits together into meaningful arrangements such
that they can be treated as a single entity. Bits are
framed not only for convenience but also for purposes of
error checking and correction. |
| Frequency |
The number of
occurrences per unit time of a complete wavelength (one
positive and one negative alternation). Frequency is
measured in hertz (Hz), sometimes referred to as CPS. |
| Frequency-Division
Multiplexing |
(FDM) Consists
of separate channels that are assigned to individual
frequencies across the frequency bandwidth on a common
transmission facility. ADSL technology, for example, has
a frequency range of 30 kHz to 1.1 MHz that can be
divided into two nonoverlapping areas used for upstream
and downstream transmission. |
| FTP |
File
Transfer Protocol. Internet tool for sending and/or
receiving files from a server linked to the Internet. |
| FTTC |
Fiber To The
Curb. Network where an optical fiber runs from the
telephone switch to a curbside distribution point close
to the subscriber where it is converted to copper pair. |
| FTTH |
Fiber To The
Home. Network where an optical fiber runs from the
telephone switch to the subscriber's premises. |
| G.lite
ADSL |
The
G.lite standard was specifically developed to meet the
plug-and-play requirements of the consumer market
segment. G.lite is a medium bandwidth version of ADSL
that allows Internet access at up to 30 times the speed
of the fastest 56K analog modems ~ up to 1.5 megabits
downstream and up to 500 kilobits upstream. G.lite is an
International Telecommunications Union (ITU) standard,
globally standardized interoperable ADSL system per ITU
G.992.2. |
| Graphical
User Interface |
(GUI) A
computer environment, such as Microsoft Windows or MacOS,
that graphically represents programs, activities and
services, and is typically manipulated through both
keyboard and mouse. |
| GUI |
Graphical User
Interface. A computer environment, such as Microsoft
Windows or MacOS, that graphically represents programs,
activities and services, and is typically manipulated
through both keyboard and mouse. |
| HDSL |
High
bit-rate Digital Subscriber Line. An xDSL technology
providing symmetrical transmission at 1.544 Mbps over 24
DS0 channels on two wire pairs. |
| HDSL2 |
High
bit-rate Digital Subscriber Line 2nd Generation. An xDSL
technology that is a variation of HDSL. HDSL-2 provides
symmetrical transmission of 24 DS0 at 1.544 Mbps on a
one-wire pair (versus two wire pairs of HDSL). HDSL-2
uses Trellis-coded pulse amplitude modulation (TC-PAM)
as a line code. |
| HFC |
Hybrid Fiber
Coax |
| High
bit-rate Digital Subscriber Line |
(HDSL)
An xDSL technology providing symmetrical transmission at
1.544 Mbps over 24 DS0 channels on two wire pairs. |
| High
bit-rate Digital Subscriber Line 2nd Generation |
(HDSL2)
An xDSL technology that is a variation of HDSL. HDSL-2
provides symmetrical transmission of 24 DS0 at 1.544
Mbps on a one-wire pair (versus two wire pairs of HDSL).
HDSL-2 uses Trellis-coded pulse amplitude modulation (TC-PAM)
as a line code. |
| High
Speed Concentrators |
A
multi-protocol computer device that aggregates lower
speed connections into broadband circuits. |
| High-bit-rate
Digital Subscriber Line Transceiver Unit - Central
Office |
HTU-C |
| High-bit-rate
Digital Subscriber Line Transceiver Unit - Remote |
HTU-R |
| HTU-C |
High-bit-rate
Digital Subscriber Line Transceiver Unit - Central
Office |
| HTU-R |
High-bit-rate
Digital Subscriber Line Transceiver Unit - Remote |
| Hybrid
Fiber Coax |
HFC |
