|
ADSL
Asymmetric Digital Subscriber Line. A
high-speed Internet access technology used for the Bell Sympatico
High Speed Edition service, by Bell in parts of Ontario and
Quebec. A technology in which high-capacity transmission
requirements, such as compressed video signals are delivered
through copper wire. In this case, "asymmetric" refers
to the transmission capacity towards the customer being greater
than that from the customer to the network.
Bandwidth
The amount of data that can be transmitted over a given time
period.
Bit
A contraction of the "binary digit". A bit is the
smallest possible unit of storage of computer information and can
be one of two values. These values are typically represented by 0
and 1, low and high, or on and off.
bps
bits-per-second. A measure of data transmission, such as that
handled by a modem.
Broadband
A communications medium which is capable of carrying multiple
messages at the same time.
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 (roaming)
Ability to access the Internet through a dial up connection.
Dial
Up
The use of a rotary-dial or Touch-Tone™ telephone to initiate a
station-to-station telephone call.
DSL
Digital Subscriber Line. A term coined
to refer to the family of DSL access technologies, including ADSL,
RADSL, VDSL, etc.
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™; 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.
HFC
Hybrid Fibre-Coaxial. A high speed
Internet access technology not yet employed by the Sympatico
service.
Internet
A wide-area network that connects tens of millions of computers
worldwide. Originally implemented by the U.S. Defence Department,
Internet is now administered by an independent organization.
Members include: government agencies, educational institutions and
large corporations.
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).
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
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.
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.
Splitterless
"Splitterless ADSL" refers to
the fact that this particular version of the technology does not
require an in-house installation by a qualified technician of a
special filter known as a POTS Splitter. Instead, the splitterless
ADSL service relies on the installation of small in-line filters
at each telephone set.
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.
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.
VADSL
Very-High-Rate Asymmetric Digital
Subscriber Line. A high-speed Internet access technology.
Web
Server
This is a computer that delivers (serves up) Web pages. Every Web
server has an IP address and possibly a domain name. For example,
if you enter the URL http://www1.sympatico.ca/Tools/ into your
browser, a request is sent to the server with the domain name:
sympatico.ca. The server then fetches the page named Tools and
sends it to your browser. Any
computer can be turned into a Web server by installing server
software and connecting it to the Internet. There are many Web
server software applications, including public domain software
from NCSA and commercial packages from Microsoft, Netscape, and
others.
|
