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EtherFast
®
Cable/DSL Routers
CSMA/CD (Carrier Sense Multiple Access/Collision Detection) - The LAN
access method used in Ethernet. When a device wants to gain access to the net-
work, it checks to see if the network is quiet (senses the carrier). If it is not, it
waits a random amount of time before retrying. If the network is quiet and two
devices access the line at exactly the same time, their signals collide. When the
collision is detected, they both back off and each waits a random amount of
time before retrying.
Daisy Chain - Connected in series, one after the other. Transmitted signals go
to the first device, then to the second, and so on.
Database - A database is a collection of data that is organized so that its con-
tents can easily be accessed, managed, and updated.
Data Packet - One frame in a packet-switched message. Most data communi-
cations is based on dividing the transmitted message into packets. For example,
an Ethernet packet can be from 64 to 1518 bytes in length.
Default Gateway - The routing device used to forward all traffic that is not
addressed to a station within the local subnet.
DHCP (Dynamic Host Configuration Protocol) - A protocol that lets network
administrators centrally manage and automate the assignment of Internet
Protocol (IP) addresses in an organization's network. Using the Internet’s set of
protocol (TCP/IP), each machine that can connect to the Internet needs a
unique IP address. When an organization sets up its computer users with a con-
nection to the Internet, an IP address must be assigned to each machine.
Without DHCP, the IP address must be entered manually at each computer and,
if computers move to another location in another part of the network, a new IP
address must be entered. DHCP lets a network administrator supervise and dis-
tribute IP addresses from a central point and automatically sends a new IP
address when a computer is plugged into a different place in the network.
DHCP uses the concept of a “lease” or amount of time that a given IP address
will be valid for a computer. The lease time can vary depending on how long a
user is likely to require the Internet connection at a particular location. It’s espe-
cially useful in education and other environments where users change fre-
quently. Using very short leases, DHCP can dynamically reconfigure networks
in which there are more computers than there are available IP addresses.
DHCP supports static addresses for computers containing Web servers that
need a permanent IP address.
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Instant Broadband
™
Series
Broadband - A data-transmission scheme in which multiple signals share the
bandwidth of a medium. This allows the transmission of voice, data, and video
signals over a single medium. Cable television uses broadband techniques to
deliver dozens of channels over one cable.
Browser - A browser is an application program that provides a way to look at
and interact with all the information on the World Wide Web or PC. The word
“browser” seems to have originated prior to the Web as a generic term for user
interfaces that let you browse text files online.
Cable Modem - A device that connects a computer to the cable television net-
work, which in turn connects to the Internet. Once connected, cable modem
users have a continuous connection to the Internet. Cable modems feature
asymmetric transfer rates: around 36 Mbps downstream (from the Internet to
the computer), and from 200 Kbps to 2 Mbps upstream (from the computer to
the Internet).
CAT 3 - ANSI/EIA (American National Standards Institute/Electronic
Industries Association) Standard 568 is one of several standards that specify
“categories” (the singular is commonly referred to as “CAT”) of twisted pair
cabling systems (wires, junctions, and connectors) in terms of the data rates
that they can sustain. CAT 3 cable has a maximum throughput of 16 Mbps and
is usually utilized for 10BaseT networks.
CAT 5 - ANSI/EIA (American National Standards Institute/Electronic
Industries Association) Standard 568 is one of several standards that specify
“categories” (the singular is commonly referred to as “CAT”) of twisted pair
cabling systems (wires, junctions, and connectors) in terms of the data rates
that they can sustain. CAT 5 cable has a maximum throughput of 100 Mbps and
is usually utilized for 100BaseTX networks.
CAT 5e - The additional cabling performance parameters of return loss and far-
end crosstalk (FEXT) specified for 1000BASE-T and not specified for
10BASE-T and 100BASE-TX are related to differences in the signaling imple-
mentation. 10BASE-T and 100BASE-TX signaling is unidirectional—signals
are transmitted in one direction on a single wire pair. In contrast, Gigabit
Ethernet is bi-directional—signals are transmitted simultaneously in both
directions on the same wire pair; that is, both the transmit and receive pair
occupy the same wire pair.
CPU (Central Processing Unit) - The computing part of the computer. Also
called the “processor,” it is made up of the control unit and ALU.
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