Network Everywhere NWP11B, Руководство пользователя

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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.
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 (Direct-Sequence Spread Spectrum) - 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.
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 (Frequency Hopping Spread Spectrum) - 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.
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Boot - To cause the computer to start executing instructions. Personal comput-
ers contain built-in instructions in a ROM chip that are automatically executed
on startup. These instructions search for the operating system, load it and pass
control to it.
BSS (Basic Service Set) - An infrastructure network connecting wireless
devices to a wired network using a single access point.
Cardbus - A high-speed peripherals interface for notebook PCs that delivers
32-bit performance based on PCI bus architecture.
CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) - In local
area networking, this is the CSMA technique that combines slotted time-divi-
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.
CTS (Clear To Send) - An RS-232 signal sent from the receiving station to the
transmitting station that indicates it is ready to accept data.
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 (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 espe-
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Wireless Notebook Adapter Network Everywhere ™ Series