Wireless-B Notebook Adapter
34
33
Driver
- A workstation or server software module that provides an interface
between a network interface card and the upper-layer protocol software running
in the computer; it is designed for a specific NIC, and is installed during the
initial installation of a network-compatible client or server operating system.
DSSS
(
D
irect-
S
equence
S
pread
S
pectrum) - DSSS generates a redundant bit
pattern for all data transmitted. This bit pattern is called a chip (or chipping
code). Even if one or more bits in the chip are damaged during transmission,
statistical techniques embedded in the receiver can recover the original data
without the need for retransmission. To an unintended receiver, DSSS appears
as low power wideband noise and is rejected (ignored) by most narrowband
receivers. However, to an intended receiver (i.e. another wireless LAN end-
point), the DSSS signal is recognized as the only valid signal, and interference
is inherently rejected (ignored).
Encryption
- A security method that applies a specific algorithm to data in
order to alter the data's appearance and prevent other devices from reading the
information.
ESS
(
E
xtended
S
ervice
S
et) - A set of more than two or more BSSs (multiple
access points) forming a single network.
Ethernet
- IEEE standard network protocol that specifies how data is placed
on and retrieved from a common transmission medium. Has a transfer rate of
10 Mbps. Forms the underlying transport vehicle used by several upper-level
protocols, including TCP/IP and XNS.
FHSS
(
F
requency
H
opping
S
pread
S
pectrum) - FHSS continuously changes
(hops) the carrier frequency of a conventional carrier several times per second
according to a pseudo-random set of channels. Because a fixed frequency is not
used, and only the transmitter and receiver know the hop patterns, interception
of FHSS is extremely difficult.
Fragmentation
- Breaking a packet into smaller units when transmitting over
a network medium that cannot support the original size of the packet.
Gateway
- A device that interconnects networks with different, incompatible
communications protocols.
Hardware
- Hardware is the physical aspect of computers, telecommunica-
tions, and other information technology devices. The term arose as a way to dis-
tinguish the "box" and the electronic circuitry and components of a computer
Instant Wireless
®
Series
sion multiplexing with carrier sense multiple access/collision detection
(CSMA/CD) to avoid having collisions occur a second time. This works best if
the time allocated is short compared to packet length and if the number of sit-
uations is small.
Database
- A database is a collection of data that is organized so that its con-
tents can easily be accessed, managed, and updated.
Default Gateway
- The routing device used to forward all traffic that is not
addressed to a station within the local subnet.
DHCP
(
D
ynamic
H
ost
C
onfiguration
P
rotocol) - 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 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.
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.
Domain
- A subnetwork comprised of a group of clients and servers under the
control of one security database. Dividing LANs into domains improves per-
formance and security.
