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“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 16Mbps 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 100Mbps 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 implementation.
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-direc-
tional—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.
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.
DHCP (Dynamic Host Configuration Protocol) - A protocol that lets network
administrators manage centrally 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
especially 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.
Glossary
10BaseT - An Ethernet standard that uses twisted wire pairs.
100BaseTX - IEEE physical layer specification for 100Mbps over two pairs of
Category 5 UTP wire.
1000BASE-T - Provides half-duplex (CSMA/CD) and full-duplex 1000Mbps
Ethernet service over Category 5e links as defined by ANSI/TIA/EIA-568-A.
Topology rules for 1000Base-T are the same as those used for 100Base-TX.
Category 5e link lengths are limited to 100 meters by the ANSI/TIA/EIA-568-
A cabling standard. Only one CSMA/CD repeater will be allowed in a collision
domain.
Adapter - Printed circuit board that plugs into a PC to add capabilities or con-
nectivity to a PC. In a networked environment, a network interface card (NIC)
is the typical adapter that allows the PC or server to connect to the intranet
and/or Internet.
ARP (Address Resolution Protocol) - A TCP/IP protocol used to figure out a
host’s Ethernet address from its Internet address.
Auto-negotiate - To automatically determine the correct settings. The term is
often used with communications and networking. For example, Ethernet
10/100 cards, hubs, and switches can determine the highest speed of the node
they are connected to and adjust their transmission rate accordingly.
Backbone - The part of a network that connects most of the systems and net-
works together and handles the most data.
Bandwidth - The transmission capacity of a given facility, in terms of how
much data the facility can transmit in a fixed amount of time; expressed in bits
per second (bps).
BOOTP (BOOTstrap Protocol) - A TCP/IP protocol that lets a device connect-
ed to the network be automatically configured and booted up. An IP address is
automatically assigned for a specific length of time.
CAT 3 - ANSI/EIA (American National Standards Institute/Electronic
Industries Association) Standard 568 is one of several standards that specify