DNS - The domain name system (DNS) is the way that Internet domain name
are located and translated into Internet Protocol (IP) addresses. A domain name
is a meaningful and easy-to-remember "handle" for an Internet address.
DSSS - Also known as “Direct Sequence Spred Spectrum”, this is a variety of
radio transmission methods that continuously change frequencies or signal pat-
terns. Direct sequence spread spectrum (DSSS), which is used in CDMA, mul-
tiplies the data bits by a very fast pseudo-random bit pattern (PN sequence) that
"spreads" the data into a large coded stream that takes the full bandwidth of the
channel
Dynamic IP Address - An IP address that is automatically assigned to a client
station in a TCP/IP network, typically by a DHCP server. Network devices that
serve multiple users, such as servers and printers, are usually assigned static IP
addresses.
ESS - More than one BSS in a network.
FHSS - Also known as “Frequency Hopping Spread Spectrum”. Frequency
hopping spread spectrum (FHSS) continuously changes the center frequency of
a conventional carrier several times per second according to a pseudo-random
set of channels, while chirp spread spectrum changes the carrier frequency.
Because a fixed frequency is not used, illegal monitoring of spread spectrum
signals is extremely difficult, if not downright impossible depending on the
particular method.
Firewall - A firewall is a set of related programs, located at a network gateway
server, that protects the resources of a network from users from other networks.
(The term also implies the security policy that is used with the programs.) An
enterprise with an intranet that allows its workers access to the wider Internet
installs a firewall to prevent outsiders from accessing its own private data
resources and for controlling what outside resources to which its own users
have access.
Basically, a firewall, working closely with a router program, examines each
network packet to determine whether to forward it toward its destination.
Firmware - Programming that is inserted into programmable read-only mem-
ory (programmable read-only memory), thus becoming a permanent part of a
computing device.
78
Glossary
Ad-hoc Network - An ad-hoc network is a wireless network or other small net-
work in which some of the network devices are part of the network only for the
duration of a communications session while in some close proximity to the rest
of the network.
BSS (Basic Service Set) - A group of Instant Wireless
TM
Network PC Card
users and a Wireless AP + Cable/DSL Router.
Default Gateway - The router used to forward all traffic that is not addressed
to a station within the local subnet.
DHCP (Dynamic Host Configuration Protocol) - Aprotocol 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 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.
DMZ - A DMZ (demilitarized zone) is a computer host or small network
inserted as a "neutral zone" between a company's private network and the out-
side public network. It prevents outside users from getting direct access to a
server that has company data.
77
Etherfast
®
Wireless AP + Cable/DSL Router with PrintServerInstant Broadband
TM
Series
