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56K
The term 56K refers to a new
generation of modems that improve the
speed of communication between personal
computers and the Internet. The previous
speed standard of v.34 provided
communication at speeds as high as
33,600 bits per second (bps). The new
56K modems increase that speed to a
theoretical maximum of 57,600 or 56
Kbps. In the past, two different
technologies emerged enabling 56K
communication: K56flex and x2. They have
been replaced by a new, international
standard for 56K data communications
known as v.90.
ADSL
Asymmetric Digital Subscriber Line (ADSL) is the most popular form of DSL
technology.
ADSL
Lite
A lower data rate version of
Asymmetric Digital Subscriber Line (ADSL).
Bandwidth
The amount of data that can be
transmitted over a given time
Bit
A contraction of the "binary
digit". A bit is the smallest
possible unit of storage of computer
information and can one of two values.
These values are typically represented
by 0 and 1, low and high, or on and off.
Broadband
A term for high-speed, high-capacity
Internet and data connections.
CAP
Carrier-less Amplitude/Phase (CAP)
modulation; incoming data modulates a
single carrier that is then transmitted
down a telephone line. The carrier
itself is suppressed before transmission
(it contains no information, and can be
reconstructed at the receiver), hence
the adjective "carrier-less."
CAP and DMT are two modulation systems
currently on the market for ADSL.
Dedicated
Access
A direct connection between a
terminal and a service, network or
computer dedicated to the specific use
of a particular customer.
Dial access
Ability to access the Internet
through a dial up connection.
DMT
Discrete Multi-Tone (DMT)
multi-carrier modulation uses 256 QAM
modulation tones simultaneously to
create the ADSL signal. DMT is the basis
of ANSI Standard T1.413, and has the
support of other world standards bodies.
CAP and DMT are two modulation systems
currently on the market for ADSL.
DSL
Digital Subscriber Line (DSL)
provides a dedicated digital circuit
between a residence and a telephone
company's central office, allowing
high-speed data transport over existing
twisted copper telephone lines.
EtherLoop
EtherLoop is currently a proprietary
technology from Nortel, short for
Ethernet Local Loop.
E-mail address
Electronic identification that
enables users to send and receive
electronic mail
Ethernet
card
The ethernet card provides a
standardized way of connecting computers
together to create a network. Because
DSL technology requirements far exceeds
the lower speed limits of standard
serial/parallel connections now uilt-in
most PCs, a connection technology
capable of interfacing at higher speeds
was required; Ethernet technology,
capable of sustaining traffic volumes of
up to 10MB, was chosen as the technology
of choice.
Filter
A device that prevents noise
interference and is installed between a
telephone and its wall jack.
Firewall
A system designed to prevent
unauthorized access to or from a private
network. Firewalls can be implemented in
both hardware and software, or a
combination of both. Firewalls are
frequently used to prevent unauthorized
Internet users from accessing private
networks connected to the Internet,
especially Intranets. All messages
entering or leaving the Intranet pass
through the firewall, which examines
each message and blocks those that do
not meet the specified security
criteria. A firewall is considered a
first line of defense in protecting
private information. For greater
security, data can be encrypted.
There are several types of firewall
techniques:
Packet filter:
Looks at each packet entering or leaving
the network and accepts or rejects it
based on user-defined rules. Packet
filtering is fairly effective and
transparent to users, but it is
difficult to configure. In addition, it
is susceptible to IP spoofing.
Application
gateway: Applies security
mechanisms to specific applications,
such as FTP and Telnet servers. This is
very effective, but can impose
performance degradation.
Circuit-level
gateway: Applies security
mechanisms when a TCP(tm); or UDP
connection is established. Once the
connection has been made, packets can
flow between the hosts without further
checking.
Proxy server:
Intercepts all messages entering and
leaving the network. The proxy server
effectively hides the true network
addresses.
Gateway
This is a device that converts
different protocols; a network
interconnectivity device that translates
communications protocols.
In networking, it is a combination of
hardware and software that links two
different types of networks. Gateways
between e-mail systems, for example,
allow users on different e-mail systems
to exchange messages.
Gateway
Address
A gateway address is the IP address
of a network point that acts as an
entrance to another network. For
example, in a corporate network, a proxy
server acts as a gateway between the
internal network and the Internet.
Hub
A common connection point for all
devices connected to a star network. A
passive hub simply serves as a conduit
for the data, enabling it to go from one
device to another. So called intelligent
hubs include additional features that
enable them to act as a bridge,
transferring data between different
types of networks. Some hubs are
full-fledged computers that also act as
network servers.
HDSL
High Bit-rate Digital Subscriber
Line (HDSL) is generally used as a
substitute for T1/E1.
Internet
A wide-area network that connects
tens of millions of computers worldwide.
Originally implemented by the U.S.
Defense Department, Internet is now
administered by an independent
organization.
IDSL
ISDN based DSL developed originally
by Ascend Communications.
Kbps
Kilobits-per-second (thousands of
bits-per-second). A measure of data
transmission, such as that handled by a
modem.
Line
A communications channel. Also
called a circuit, trunk or facility. It
often refers to customer access to the
public switched telephone network (e.g.,
residence line, individual business
line).
LAN
Local Area Networks.
Mbps
Megabits-per-second (millions of
bits-per-second). A measure of data
transmission, such as that handled by a
modem.
Modem
Device that modulates and
demodulates data usually transmitted
over a regular telephone line
MSO
Multiple service operator synonymous
with cable provider.
NAP
Network Access Point (NAP) is a
high-speed interconnection service that
gives Internet Service Providers access
to the new Internet infrastructure.
NIC
Network Interface Card; an Ethernet
adapter "PC card" that needs
to be installed in the computer when
certain DSL modems are used. Along with
the modem, the NIC enables the DSL
connection at the customer's home or
business.
Network
A series of points interconnected by
telecommunications channels
Port
The entrance or access point to a
computer or multiplexer.
Proxy
Server
A server that sits between a client
application, such as a Web browser, and
a real server. It intercepts all
requests to the real server to see if it
can fulfill the requests itself. If not,
it forwards the request to the real
server. Proxy servers can also be used
to filter requests. For example, a
company might use a proxy server to
prevent its employees from accessing a
specific set of Web sites.
PVC
Private Virtual Circuit (PVC) is a
point-to-point circuit from the customer
premise equipment to either their
Internet Service Provider (ISP) or
Enterprise Network.
Router
A device that connects two LANs.
Routers are similar to bridges, but
provide additional functionality, such
as the ability to filter messages and
forward them to different places based
on various criteria. The Internet uses
routers extensively to forward packets
from one host to another.
RADSL
Rate Adaptive Digital Subscriber
Line (RADSL) is any rate adaptive DSL
modem, but may specifically refer to a
proprietary modulation standard designed
by Globespan Semiconductor.
Streaming
A method of delivering information
(usually sound and/or video) over the
Internet such that it can be played on a
receiving computer at the same time it
is being delivered.
Subnet
A portion of a network that shares a
common address component. On TCP/IP
networks, subnets are defined as all
devices whose IP addresses have the same
prefix. For example, all devices with IP
addresses that start with 100.100.100
would be part of the same subnet.
Dividing a network into subnets is
useful for both security and performance
reasons. IP networks are divided using a
subnet mask.
Symmetric Digital Subscriber Line
(SDSL) is a 2-wire implementation of (HDSL).
Telnet
A terminal emulation program for
TCP/IP networks such as the Internet.
The Telnet program runs on your computer
and connects your PC to a server on the
network. You can then enter commands
through the Telnet program and they will
be executed as if you were entering them
directly on the server console. This
enables you to control the server and
communicate with other servers on the
network. To start a Telnet session, you
must log into a server by entering a
valid username and password. Telnet is
the most common way to remotely control
Web servers.
v.90
A new, international standard for
56K data communications.
VDSL
Very High Bit-rate Digital
Subscriber Line (VDSL) is proposed for
shorter local loops, perhaps up to 3000
ft.
WAN
Wide area networks.
XDSL
Refers to the family of digital
subscriber line technologies, such as
ADSL, HDSL, and RADSL. |
