Glossary
ADSL - (Asymmetric Digital Subscriber Line) :
A technology for transmitting digital information at high
speeds on existing copper phone lines to homes and businesses. ADSL is
asymmetric in that it uses most of the channel to transmit downstream to
the user and only a small part to receive information from the user.
ADSL simultaneously accommodates POTS (plain old telephone service) and
can transmit data at speeds ranging from 1.544 Mbps to 8 Mbps.
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Analog : Electronic
transmission accomplished by adding signals of varying frequency or
amplitude to carrier waves of a given frequency of alternating
electromagnetic current. Broadcast and phone transmission have
conventionally used analog technology.
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ATM - (Asynchronous Transfer Mode) :
A dedicated-connection switching technology that
organizes digital data into 53-byte cells or packets and transmits them
over a medium using digital signal technology. Individually, a cell is
processed asynchronously relative to other related cells and is queued
before being multiplexed over the line.
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Backbone : In a network,
a backbone is a larger transmission path into which smaller lines feed.
On the Internet or other wide area network, a backbone is a set of paths
that local or regional networks connect to for long-distance
interconnection. The connection points are known as network nodes or
telecommunication data switching exchanges (DSEs).
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Bandwidth : In digital
systems, bandwidth refers to data speed usually measured in bits per
second (bps).
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BPS - (Bits Per Second) : In
data communications, bits per second (abbreviated bps) is a common
measure of data speed for computer modems and transmission carriers.
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Bridge : A bridge is a
product that connects a local area network (LAN) to another local area
network that uses the same protocol. You can envision a bridge as a
device that decides whether a message from you to someone else is going
to the local area network in your building or someone on the local area
network in the building across the street. A bridge examines each
message on a LAN, "passing" those known to be within the same LAN, and
forwarding those known to be on the other interconnected LAN or LANs.
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Centrex - (CENTRal office EXchange service)
: A service from local telephone companies in the
United States in which up-to-date phone facilities at the phone
company's central (local) office are offered to business users so that
they don't need to purchase their own facilities. The Centrex service
effectively partitions part of its own centralized capabilities among
its business customers.
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Channel Bank : A
device at a telephone company central office (public exchange) that
converts analog signals from home and business users into digital
signals to be carried over higher-speed lines between the central office
and other exchanges.
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CLECs - Competitive Local Exchange Carriers :
CLECs are often regional service providers that provide
dedicated access services between two locations within a state or
multi-state region. They may also partner with other CLECs to provide
dedicated access between two locations in different regions of the
country.
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CSU/DSU - (Channel/Data Service Unit) :
Receives and transmits signals from and to the WAN line
and provides a barrier for electrical interference from either side of
the unit. The CSU can also echo loop back signals from the phone company
for testing purposes. The Data Service Unit (DSU) manages line control,
and converts input and output between RS-232C, RS-449, or V.35 frames
from the LAN and the time-division multiplexed (TDM) DSX frames on the
T-1 line.
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Dedicated Access Providers
: Dedicated access services are available between
most U.S. locations and in many other countries. In the U.S., carriers
offering dedicated access service include incumbent local telephone
companies (ILECs), competitive local exchange carriers (CLECs), long
distance carriers (IXCs), and Internet service providers (ISPs).
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Digital : Electronic
technology that generates, stores, and processes data in terms of two
states: positive and non-positive. Positive is expressed or represented
by the number 1 and non-positive by the number 0. Thus, data transmitted
or stored with digital technology is expressed as a string of 0's and
1's. Each of these state digits is referred to as a bit (and a string of
bits that a computer can address individually as a group is a byte).
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DS 1 : Used as the signal in
the T-1 carrier, is 24 DS0 (64 Kbps) signals
transmitted using pulse-code modulation (PCM) and time-division
multiplexing (TDM).
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Ethernet : Ethernet is
the most widely-installed local area network technology. Now specified
in a standard, IEEE 802.3, an Ethernet LAN typically uses coaxial cable
or special grades of twisted pair wires.
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Fiber Optics :
Refers to the medium and the technology associated with the transmission
of information as light impulses along a glass or plastic wire or fiber.
Fiber optic wire carries much more information than conventional copper
wire and is far less subject to electromagnetic interference.
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Hub : In data communications,
a convergence place where data comes in from one or more directions and
is forwarded out in one or more other directions. A hub usually includes
a switch of some kind and can also include a router.
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ILECs - Incumbent Local Exchange Carriers :
With the exception of Bell Atlantic in New York state,
SBC in Texas and other states that may follow, ILECs are generally
limited to providing dedicated access services between two locations
within a LATA.
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IXC - (IntereXchange Carrier) :
A telephone company that provides connections between
local exchanges in different geographic areas. IXCs provide interLATA
service as described in the Telecommunications Act of 1996.They're
commonly referred to simply as "long-distance carriers."
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LAN - (Local Area Network) :
A network of interconnected workstations sharing the resources of a
single processor or server within a relatively small geographic area.
Typically, this might be within the area of a small office building.
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LATA - (Local Access and Transport Area) :
A term in the U.S. for a geographic area covered by one
or more local telephone companies, which are legally referred to as
local exchange carriers (LECs). A connection between two local exchanges
within the LATA is referred to as intraLATA. A connection between a
carrier in one LATA to a carrier in another LATA is referred to as
interLATA and is defined as long-distance service.
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LEC - Local Exchange Carriers :
Local Exchange Carriers are generally divided between the
incumbent local exchange carrier (usually the Regional Bell Operating
Company or RBOC) and the Competitive Local Exchange Carriers. In some
areas a CLEC may be a RBOC operating outside of its own home territory
where a different RBOC is the incumbent.
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Mbps - (MegaBits Per Second) :
In data communications, a common measure of data speed
for computer modems and transmission carriers. One megabit per second
(Mbps) is equal to 1,000,000 bps or 1,000 kbps.
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PBX - (Private Branch Exchange) :
Similar to having a telephone company central office on
your own premises. Calls can be switched from one point to another in
the system, or can be made to or received from callers outside the
system.
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PCS - (Personal Communications Service) :
A wireless phone service somewhat similar to cellular
telephone service. It's sometimes referred to as digital cellular. Like
cellular, PCS is for mobile users and requires a number of antennas to
blanket an area of coverage. As a user moves around, the user's phone
signal is picked up by the nearest antenna and then forwarded to a base
station that connects to the wired network. The phone itself is slightly
smaller than a cellular phone.
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POP - (Point of Presence) :
The location of an access point to the Internet. An internet service
provider (ISP) has a point-of-presence on the Internet.
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POTS - (Plain Old Telephone Service) :
A term sometimes used in discussion of new telephone
technologies in which the question of whether and how existing voice
transmission for ordinary phone communication can be accommodated. For
example, ADSL and ISDN provide some part of their channels for example,
ADSL and ISDN provide some part of their channels for "plain old
telephone service" while providing most of their bandwidth for digital
data transmission.
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PPP - (Point-to-Point Protocol) :
A protocol for communication between two computers using
a serial interface, typically a personal computer connected by phone
line to a server. For example, an Internet server provider may provide
you with a PPP connection so that the provider's server can respond to
your requests, pass them on to the Internet, and forward your requested
Internet responses back to you.
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Protocol : The special
set of rules for communicating that the end points in a
telecommunication connection use when they send signals back and forth
existing at several levels in a telecommunication connection. Both end
points must recognize and observe the protocol. Protocols are often
described in an industry or national standard.
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Router : A device or, in
some cases, software in a computer, that determines the next network
point to which a packet should be forwarded toward its final
destination.
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Server : A computer
program that provides services to other computer programs in the same or
other computers. The computer that a server program runs in is also
frequently referred to as a server (though it may contain a number of
server and client programs). Specific to the Web, a Web server is the
computer program (housed in a computer) that serves requested HTML pages
or files. A Web client is the requesting program associated with the
user.
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SMTP - (Simple Mail Transfer Protocol) :
A TCP/IP protocol governing electronic mail transmission
and reception.
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WAN - (Wide-area Network) :
Used to distinguish the broader telecommunication structure from a local
area network (LAN). A wide area network may be composed entirely of
private structures, but the term seems to also connote the inclusion of
public networks and all kinds of transmission media.
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