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ADSL:
The variation called ADSL (Asymmetric Digital Subscriber Line)
is the form of DSL that will become most familiar to home and
small business users. ADSL is called "asymmetric" because most
of its two-way or duplex bandwidth is devoted to the downstream
direction, sending data to the user. Only a small portion of
bandwidth is available for upstream or user-interaction messages.
However, most Internet and especially graphics- or multi-media
intensive Web data need lots of downstream bandwidth, but user
requests and responses are small and require little upstream
bandwidth. |
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ATM
(Asynchronous Transfer Mode): a dedicated-connection
switching technology that organizes digital data into 53-byte
cell units and transmits them over a physical medium using digital
signal technology. Individually, a cell is processed asynchronously
relative to other related cells and is queued before being multiplexed
over the transmission path. Because ATM is designed to be easily
implemented by hardware (rather than software), faster processing
and switch speeds are possible. ATM runs as a layer on top of
SONET. |
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Bandwidth:
Bandwidth (the width of a band of electromagnetic frequencies)
is used to mean (1) how fast data flows on a given transmission
path, and (2), somewhat more technically, the width of the range
of frequencies that an electronic signal occupies on a given
transmission medium. Any digital or analog signal has a bandwidth.
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Bridge:
In telecommunication networks, a bridge is a product that connects
a local area network (LAN) to another local area network that
uses the same protocol (for example, Ethernet or token ring).
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CAT
5: ANSI/EIA (American National Standards Institute/Electronic
Industries Association) Standard 568 is one of several standards
that specify "categories" of twisted pair cabling systems (wires,
junctions, and connectors) in terms of the data rates that they
can sustain. The specifications describe the cable material
as well as the types of connectors and junction blocks to be
used in order to conform to a category. The two most popular
specifications are CAT 3 and CAT 5. While the two cables may
look identical, CAT 3 is tested to a lower set of specifications
and can cause transmission errors if pushed to faster speeds.
| Category |
Maximum Data Rate
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Usual Application
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| CAT 3 |
16 Mbps |
Voice and data on 10BASE-T Ethernet
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| CAT 5 |
100 Mbps |
100 Mbps TPDDI
155 Mbps asynchronous transfer mode
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Central
Office: In telephone communication in the United States,
a central office (CO) is an office in a locality to which subscriber
home and business lines are connected on what is called a local
loop. The central office has switching equipment that can switch
calls locally or to long-distance carrier phone offices. |
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Coaxial
Cable: Coaxial cable is the kind of copper cable used
by cable TV companies between the community antenna and user
homes and businesses. Coaxial cable is sometimes used by telephone
companies from their central office to the telephone poles near
users. It is also widely installed for use in business and corporation
Ethernet and other types of local area network. |
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Co-location:
the provision of space for a customer's telecommunications equipment
on the service provider's premises. Pure play co-location operators
specialize in supplying the basics of premises, power and connectivity
to the highest standards. They leverage economies of scale to
provide absolute reliability at a commodity price. Value-added
co-location operators supplement the basic co-location offering
with optional services such as accelerated content distribution,
utility storage and security. |
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Dedicated
Access: see Dedicated Line |
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Dedicated
Line: A dedicated line is a telecommunications path between
two points that is available 24 hours a day for use by a designated
user (individual or company). It is not shared in common among
multiple users as dial-up lines are. Also called a nonswitched
line. |
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Dedicated
Hosting: see Dedicated Server |
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Dedicated
Server: In the Web hosting business, a dedicated server
refers to the rental and exclusive use of a computer that includes
a Web server, related software, and connection to the Internet,
housed in the Web hosting company's premises. A dedicated server
is usually needed for a Web site (or set of related company
sites) that may develop a considerable amount of traffic. The
server can usually be configured and operated remotely from
the client company. The use of a dedicated server saves the
client router, Internet connection, security system, and network
administration costs. |
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Dial-up:
a telephone connection in a system of many lines shared by many
users. A dial-up connection is established and maintained for
a limited time duration. The alternative is a dedicated connection,
which is continuously in place. Also called a switched line.
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DSL
(Digital Subscriber Line): a technology for bringing
high-bandwidth information to homes and small businesses over
ordinary copper telephone lines. A DSL line can carry both data
and voice signals and the data part of the line is continuously
connected. |
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Ethernet:
the most widely installed LAN technology. An Ethernet LAN typically
uses coaxial cable or special grades of twisted pair wires.
The most commonly installed Ethernet systems are called 10BASE-T
and provide transmission speeds up to 10 Mbps. Fast Ethernet
or 100BASE-T provides transmission speeds up to 100 megabits
per second and is typically used for LAN backbone systems, supporting
workstations with 10BASE-T cards. Gigabit Ethernet provides
an even higher level of backbone support at 1000 megabits per
second (1 gigabit or 1 billion bits per second). |
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Fiber
Optic: refers to the medium and the technology associated
with the transmission of information as light pulses along a
glass or plastic wire or fiber. Optical fiber carries much more
information than conventional copper wire and is in general
not subject to electromagnetic interference and the need to
retransmit signals. Most telephone company long-distance lines
are now of optical fiber. Transmission on optical fiber wire
requires repeater at distance intervals. The glass fiber requires
more protection within an outer cable than copper. For these
reasons and because the installation of any new wiring is labor-intensive,
few communities yet have optical fiber wires or cables from
the phone company's branch office to local customers (known
as local loop). |
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FTP
(File Transfer Protocol): the simplest way to exchange
files between computers on the Internet. Like the Hypertext
Transfer Protocol (HTTP), which transfers displayable Web pages
and related files, and the Simple Mail Transfer Protocol (SMTP),
which transfers e-mail, FTP is an application protocol that
uses the Internet's TCP/IP protocols. FTP is commonly used to
transfer Web page files from their creator to the computer that
acts as their server for everyone on the Internet. It's also
commonly used to download programs and other files to your computer
from other servers. |
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Gateway:
A gateway is a network point that acts as an entrance to another
network. On the Internet, a node or stopping point can be either
a gateway node or a host (end-point) node. Both the computers
of Internet users and the computers that serve pages to users
are host nodes. The computers that control traffic within your
company's network or at your local Internet service provider
(ISP) are gateway nodes. |
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Gbps:
Gbps stands for thousands of bits or kilobits per second is
a measure of bandwidth (the total information flow over a given
time) on a telecommunications medium. Depending on the medium
and the transmission method, bandwidth is sometimes measured
in the Mbps (millions of bits per second or megabits per second)
range or the Kbps (thousands of bits or kilobits per second).
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Hub:
the central part of a wheel where the spokes come together.
The term is familiar to frequent fliers who travel through airport
"hubs" to make connecting flights from one point to another.
In data communications, a hub is a place of convergence where
data arrives 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 a product that is called a "switch" could
usually be considered a hub as well.) The distinction seems
to be that the hub is the place where data comes together and
the switch is what determines how and where data is forwarded
from the place where data comes together. Regarded in its switching
aspects, a hub can also include a router. |
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IP
(Internet Protocol): the method by which data is sent
from one computer to another on the Internet. Each computer
(known as a host) on the Internet has at least one IP address
that uniquely identifies it from all other computers on the
Internet. When you send or receive data the message gets divided
into packets. Each of these packets contains both the sender's
Internet address and the receiver's address. Any packet is sent
first to a gateway computer that understands a small part of
the Internet. The gateway computer reads the destination address
and forwards the packet to an adjacent gateway that in turn
reads the destination address and so forth across the Internet
until one gateway recognizes the packet as belonging to a computer
within its immediate neighborhood or domain. That gateway then
forwards the packet directly to the computer whose address is
specified. |
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ISDN:
Integrated Services Digital Network (ISDN) is a set of CCITT/ITU
standards for digital transmission over ordinary telephone copper
wire as well as over other media. Home and business users who
install an ISDN adapter (in place of a modem) can see highly-graphic
Web pages arriving very quickly (up to 128 Kbps). ISDN requires
adapters at both ends of the transmission so your access provider
also needs an ISDN adapter. |
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Kbps:
Kbps stands for thousands of bits or kilobits per second is
a measure of bandwidth (the total information flow over a given
time) on a telecommunications medium. Depending on the medium
and the transmission method, bandwidth is sometimes measured
in the Mbps (millions of bits per second or megabits per second)
range or the Gbps (billions of bits or gigabits per second)
range. |
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LAN
(Local Area Network): a group of computers and associated
devices that share a common communications line and typically
share the resources of a single processor or server within a
small geographic area (for example, within an office building).
Usually, the server has applications and data storage that are
shared in common by multiple computer users. A local area network
may serve as few as two or three users or many as thousands
of users. |
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Mbps:
Mbps stands for millions of bits per second or megabits per
second and is a measure of bandwidth (the total information
flow over a given time) on a telecommunications medium. Depending
on the medium and the transmission method, bandwidth is sometimes
measured in the Kbps (thousands of bits or kilobits per second)
range or the Gbps (billions of bits or gigabits per second)
range. |
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Modem:
used to convert the digital information in your computer to
analog signals for your phone line and to convert analog phone
signals to digital information for your computer. |
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Point-of-presence
(POP): an access point to the Internet. A POP necessarily
has a unique Internet Protocol (IP) address. Your Internet service
provider (ISP) or online service provider has a point-of-presence
on the Internet and probably more than one. The number of POPs
that an ISP or OSP has is sometimes used as a measure of its
size or growth rate. |
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RADSL:
RADSL (Rate-Adaptive DSL) is an ADSL technology in which software
is able to determine the rate at which signals can be transmitted
on a given customer phone line and adjust the delivery rate
accordingly. |
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Router:
On the Internet, a router is 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 destination. The router
is connected to at least two networks and decides which way
to send each information packet based on its current understanding
of the state of the networks it is connected to. A router is
located at any gateway (where one network meets another), including
each Internet point-of-presence. A router is often included
as part of a network switch. |
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SDSL
(Symmetric Digital Subscriber Line): DSL in which the
data rate is the same for both upstream and downstream transmission.
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Server:
1) a computer program that provides services to other computer
programs in the same or other computers; 2) the computer on
which a server program runs; 3) in the client/server programming
model, a server is a program that awaits and fulfills requests
from client programs in the same or other computers. A given
application in a computer may function as a client with requests
for services from other programs and also as a server of requests
from other programs; 4) see also Web Server. |
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Shared
Hosting: hosting in which the service provider serves
pages for multiple Web sites, each having its own Internet domain
name, from a single Web server. Although shared hosting is a
less expensive way for businesses to create a Web presence,
it is usually not sufficient for Web sites with high traffic.
These sites need a dedicated Web server, either provided by
a Web hosting service or maintained in-house. |
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SONET
(Synchronous Optical Network): the US standard for synchronous
data transmission on optical media. SONET ensures standards
so that digital networks can interconnect internationally and
that existing conventional transmission systems can take advantage
of optical media through tributary attachments. SONET provides
standards for a number of line rates up to the maximum line
rate of 9.953 Gbps. Actual line rates approaching 20 gigabits
per second are possible. SONET is considered to be the foundation
for the physical layer of the broadband ISDN. |
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Switch:
In telecommunications, a switch is a network device that selects
a path or circuit for sending a unit of data to its next destination.
A switch may also include the function of the router, a device
or program that can determine the route and specifically what
adjacent network point the data should be sent to. In general,
a switch is a simpler and faster mechanism than a router, which
requires knowledge about the network and how to determine the
route. |
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T-1:
the most commonly used digital line in the United States, Canada,
and Japan. In these countries, it carries 24 pulse code modulation
(PCM) signals using time-division multiplexing (TDM) at an overall
rate of 1.544 million bits per second (Mbps). T1 lines use copper
wire and span distances within and between major metropolitan
areas. |
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Token
Ring: A token ring network is a local area network (LAN)
in which all computers are connected in a ring or star topology
and a binary digit- or token-passing scheme is used in order
to prevent the collision of data between two computers that
want to send messages at the same time. The token ring protocol
is the second most widely used protocol on local area networks
after Ethernet. |
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Twisted
Pair Cable: Twisted-pair cable consists of copper wires
surrounded by an insulator. Two wires are twisted together (the
twisting prevents interference problems) to form a pair, and
the pair forms a circuit that can transmit data. A cable is
a bundle of one or more twisted pairs surrounded by an insulator.
Unshielded twisted-pair (UTP) is the most commonly used type
of twisted-pair cable. Shielded twisted-pair (STP) provides
protection against cross-talk. Twisted-pair cable is now commonly
used in Ethernet, Fast Ethernet, token ring, and other network
topologies. See also CAT 5. |
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Virtual
Hosting: the provision of Web server hosting service
so that a company doesn't have to purchase and maintain its
own Web server and connections to the Internet. Typically, virtual
hosting provides a customer with: domain name registration assistance,
multiple domain names that map to the registered domain name,
an allocation of file storage and directory setup for the Web
site files (HTML and graphic image files), and e-mail addresses.
The customer needs only to have a File Transfer Protocol (FTP)
program for exchanging files with the virtual host. |
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VPN:
A virtual private network (VPN) is a private data network that
makes use of the public telecommunication infrastructure, maintaining
privacy through the use of a tunneling protocol and security
procedures. The idea of the VPN is to give the company the same
capabilities at much lower cost by using the shared public infrastructure
rather than a private one. |
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WAN
(Wide Area Network): a geographically dispersed telecommunications
network. The term distinguishes a broader telecommunication
structure from a local area network (LAN). A wide area network
may be privately owned or rented, but the term usually connotes
the inclusion of public (shared user) networks. An intermediate
form of network in terms of geography is a metropolitan area
network (MAN). |
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Web
Server: the computer program that serves requested HTML
pages or files. A Web client is the requesting program associated
with the user. The Web browser is a client that requests HTML
files from Web servers. |
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Workstation:
a computer intended for individual use but faster and more capable
than a personal computer. It's intended for business or professional
use (rather than home or recreational use). |
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