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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).
Beacon Interval
-
A beacon is a packet broadcast by the Access Point to keep
the network synchronized. A beacon includes the wireless LAN service area,
the AP address, the Broadcast destination addresses, a time stamp, Delivery
Traffic Indicator Maps, and the Traffic Indicator Message (TIM).
Bit
– A binary digit. The value—0 or 1—used in the binary numbering system.
Also, the smallest form of data.
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.
Bottleneck
– A traffic slowdown that results when too many network nodes try
to access a single node, often a server node, at once.
Bridge
- A device that interconnects different networks together.
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.
Buffer
- A buffer is a shared or assigned memory area used by hardware
devices or program processes that operate at different speeds or with different
94
sets of priorities. The buffer allows each device or process to operate without
being held up by the other. In order for a buffer to be effective, the size of the
buffer and the algorithms for moving data into and out of the buffer need to be
considered by the buffer designer. Like a cache, a buffer is a “midpoint hold-
ing place” but exists not so much to accelerate the speed of an activity as to
support the coordination of separate activities.
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 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.
CPU
(
C
entral
P
rocessing
U
nit) - The computing part of the computer. Also
called the “processor,” it is made up of the control unit and ALU.
CSMA/CD
(
C
arrier
S
ense
M
ultiple
A
ccess/
C
ollision
D
etection) - 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.
CTS
(
C
lear
T
o
S
end) - 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.
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.
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Download
- To receive a file transmitted over a network. In a communications
session, download means receive, and upload means transmit.
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 transmitted data. 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).
DTIM
(
D
elivery
T
raffic
I
ndication
M
essage) - A DTIM field is a countdown
field informing clients of the next window for listening to broadcast and mul-
ticast messages. When the AP has buffered broadcast or multicast messages for
associated clients, it sends the next DTIM with a DTIM Interval value.
AP
Clients hear the beacons and awaken to receive the broadcast and multicast
messages.
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.
Dynamic Routing
- The ability for a router to forward data via a different route
based on the current conditions of the communications circuits. For example,
it can adjust for overloaded traffic or failing lines and is much more flexible
than static routing, which uses a fixed forwarding path.
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.
DDNS
(
D
ynamic
D
omain
N
ame
S
ystem) - Allows a network device with a
dynamic Internet IP address to have a fixed host and domain name, such as
myhostname.mydomainname.com
. It is useful when you are hosting your own
website, FTP server, or other server behind a router, so people can find your
site no matter how often the Internet IP address changes. Using DDNS requires
registering with a DDNS service provider on the Internet.
DHCP
(
D
ynamic
H
ost
C
onfiguration
P
rotocol) - 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.
DMZ
- (
D
e
M
ilitarized
Z
one) allows one IP address (or computer) to be
exposed to the Internet.
Some applications require multiple TCP/IP ports to be
open.
It is recommended that you set your computer with a static IP address if
you want to use DMZ Hosting.
DNS
- The Domain Name System (DNS) is the way that Internet domain
names 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.
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Fast Ethernet
- A 100 Mbps technology based on the 10Base-T Ethernet
CSMA/CD network access method.
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.
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, examines each network
packet to determine whether to forward it toward its destination.
Firmware
- Code that is written onto read-only memory (ROM) or program-
mable read-only memory (PROM).
Once firmware has been written onto the
ROM or PROM, it is retained even when the device is turned off.
Fragmentation
- Breaking a packet into smaller units when transmitting over
a network medium that cannot support the original size of the packet.
FTP
(
F
ile
T
ransfer
P
rotocol) - A protocol used to transfer files over a TCP/IP
network (Internet, UNIX, etc.). For example, after developing the HTML pages
for a website on a local machine, they are typically uploaded to the Web serv-
er using FTP.
FTP includes functions to log onto the network, list directories, and copy files.
It can also convert between the ASCII and EBCDIC character codes. FTP oper-
ations can be performed by typing commands at a command prompt or via an
FTP utility running under a graphical interface such as Windows. FTP transfers
can also be initiated from within a Web browser by entering the URL preceded
with ftp://.
Unlike e-mail programs in which graphics and program files have to be
“attached,” FTP is designed to handle binary files directly and does not add the
overhead of encoding and decoding the data.
98
Full Duplex
- The ability of a device or line to transmit data simultaneously in
both directions.
Gateway
– A device that interconnects networks with different, incompatible
communications protocols.
Half Duplex
- Data transmission that can occur in two directions over a single
line, but only one direction at a time.
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
from the program you put in it to make it do things. The program came to be
known as the software.
Hub
- The device that serves as the central location for attaching wires from
workstations. Can be passive, where there is no amplification of the signals; or
active, where the hubs are used like repeaters to provide an extension of the
cable that connects to a workstation.
HTTP
(
H
yper
T
ext
T
ransport
P
rotocol) - The communications protocol used
to connect to servers on the World Wide Web. Its primary function is to estab-
lish a connection with a Web server and transmit HTML pages to the client
browser.
IEEE
- The Institute of Electrical and Electronics Engineers. The IEEE
describes itself as “the world's largest technical professional society—promot-
ing the development and application of electrotechnology and allied sciences
for the benefit of humanity, the advancement of the profession, and the well-
being of our members.”
The IEEE fosters the development of standards that often become national and
international standards. The organization publishes a number of journals, has
many local chapters, and has several large societies in special areas, such as the
IEEE Computer Society.
Infrastructure Network
- An infrastructure network is a group of computers
or other devices, each with a wireless adapter, connected as an 802.11 wireless
LAN.
In infrastructure mode, the wireless devices communicate with each
other and to a wired network by first going through an access point.
An infra-
structure wireless network connected to a wired network is referred to as a
Basic Service Set (BSS).
A set of two or more BSS in a single network is
referred to as an Extended Service Set (ESS).
Infrastructure mode is useful at
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resources of a single processor or server within a small geographic area (for
example, within an office building).
Latency
- The time delay between when the first bit of a packet is received and
the last bit is forwarded.
MAC Address
- The MAC (Media Access Control) address is a unique num-
ber assigned by the manufacturer to any Ethernet networking device, such as a
network adapter, that allows the network to identify it at the hardware level.
Mbps
(
M
ega
B
its
P
er
S
econd) - One million bits per second; unit of measure-
ment for data transmission.
MD5
- A type of one-way authentication method that uses passwords. MD5
authentication is not as secure as the EAP-TLS or EAP/TTLS authentication
methods. MD5 authentication does not support dynamic WEP key manage-
ment.
MDI
(
M
edium
D
ependent
I
nterface) - On a network hub or switch, a MDI
port, also known as an uplink port, connects to another hub or switch using a
straight-through cable. To connect a MDI port to a computer, use a crossover
cable.
MDIX
(
M
edium
D
ependent
I
nterface Crossed) - On a network hub or switch,
a MDIX port connects to a computer using a straight-through cable. To connect
a MDIX port to another hub or switch, use a crossover cable.
mIRC
- mIRC runs under Windows and provides a graphical interface for log-
ging onto IRC servers and listing, joining, and leaving channels.
Motherboard
- A motherboard is the physical arrangement in a computer that
contains the computer’s basic circuitry and components.
Multicasting
- Sending data to a group of nodes instead of a single destination.
NAT
- NAT (Network Address Translation) is the translation of an Internet
Protocol address (IP address) used within one network to a different IP address
known within another network. One network is designated the inside network
and the other is the outside.
NetBEUI
(
NetB
IOS
E
xtended
U
ser
I
nterface) - The transport layer for
NetBIOS. NetBIOS and NetBEUI were originally part of a single protocol
suite that was later separated. NetBIOS sessions can be transported over
NetBEUI, TCP/IP, and IPX/SPX protocols.
a corporation scale, or when it is necessary to connect the wired and wireless
networks.
IP Address
- In the most widely installed level of the Internet Protocol (IP)
today, an IP address is a 32-binary digit number that identifies each sender or
receiver of information that is sent in packets across the Internet. When you
request an HTML page or send e-mail, the Internet Protocol part of TCP/IP
includes your IP address in the message (actually, in each of the packets if more
than one is required) and sends it to the IP address that is obtained by looking
up the domain name in the Uniform Resource Locator you requested or in the
e-mail address you're sending a note to. At the other end, the recipient can see
the IP address of the Web page requestor or the e-mail sender and can respond
by sending another message using the IP address it received.
IPCONFIG
- A utility that provides for querying, defining and managing IP
addresses within a network.
A commonly used utility, under Windows NT and
2000, for configuring networks with static IP addresses.
IPSec
(
I
nternet
P
rotocol
Sec
urity) - A suite of protocols used to implement
secure exchange of packets at the IP layer. IPSec supports two basic modes:
Transport and Tunnel.
Transport encrypts the payload of each packet, leaving
the header untouched, while Tunnel mode encrypts both the header and the pay-
load and is therefore more secure.
IPSec must be supported on both transmit-
ter and receiver and must share a public key.
Tunnel mode is widely deployed
in VPNs (Virtual Private Networks).
IRQ
(
I
nterrupt
R
e
Q
uest) - A hardware interrupt on a PC. There are 16 IRQ
lines used to signal the CPU that a peripheral event has started or terminated.
Except for PCI devices, two devices cannot use the same line.
ISM band
- The FCC and their counterparts outside of the U.S. have set aside
bandwidth for unlicensed use in the ISM (Industrial, Scientific and Medical)
band. Spectrum in the vicinity of 2.4 GHz, in particular, is being made avail-
able worldwide. This presents a truly revolutionary opportunity to place con-
venient high-speed wireless capabilities in the hands of users around the globe.
ISP
- An ISP (Internet service provider) is a company that provides individuals
and companies access to the Internet and other related services such as website
building and virtual hosting.
LAN
- A local area network (LAN) is a group of computers and associated
devices that share a common communications line and typically share the
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DSSS. OFDM is a scheme in which numerous signals of different frequencies
are combined to form a single signal for transmission on the medium.
OFDM works by breaking one high-speed data stream into a number of lower-
speed data streams, which are then transmitted in parallel. Each lower speed
stream is used to modulate a subcarrier. Essentially, this creates a multi-carrier
transmission by dividing a wide frequency band or channel into a number of
narrower frequency bands or sub-channels. OFDM is also used for other appli-
cations, including powerline networking.
Packet
- A unit of data routed between an origin and a destination in a network.
Packet Filtering
- Discarding unwanted network traffic based on its originat-
ing address or range of addresses or its type (e-mail, file transfer, etc.).
Partitioning
- To divide a resource or application into smaller pieces.
Passphrase
- Used much like a password, a passphrase simplifies the WEP
encryption process by automatically generating the WEP encryption keys for
Linksys products.
PC Card
- A credit-card sized removable module that contains memory, I/O,
or a hard disk.
PCI
(
P
eripheral
C
omponent
I
nterconnect) - A peripheral bus commonly used
in PCs, Macintoshes and workstations. It was designed primarily by Intel and
first appeared on PCs in late 1993. PCI provides a high-speed data path
between the CPU and peripheral devices (video, disk, network, etc.). There are
typically three or four PCI slots on the motherboard. In a Pentium PC, there is
generally a mix of PCI and ISA slots or PCI and EISA slots. Early on, the PCI
bus was known as a “local bus.”
PCI provides “plug-and-play” capability, automatically configuring the PCI
cards at startup. When PCI is used with the ISA bus, the only thing that is gen-
erally required is to indicate in the CMOS memory which IRQs are already in
use by ISA cards. PCI takes care of the rest.
PCI allows IRQs to be shared, which helps to solve the problem of limited IRQs
available on a PC. For example, if there were only one IRQ left over after ISA
devices were given their required IRQs, all PCI devices could share it. In a PCI-
only machine, there cannot be insufficient IRQs, as all can be shared.
NetBIOS
- The native networking protocol in DOS and Windows networks.
Although originally combined with its transport layer protocol (NetBEUI),
NetBIOS today provides a programming interface for applications at the ses-
sion layer (layer 5). NetBIOS can ride over NetBEUI, its native transport,
which is not routable, or over TCP/IP and IPX/SPX, which are routable proto-
cols.
NetBIOS computers are identified by a unique 15-character name, and
Windows machines (NetBIOS machines) periodically broadcast their names
over the network so that Network Neighborhood can catalog them. For TCP/IP
networks, NetBIOS names are turned into IP addresses via manual configura-
tion in an LMHOSTS file or a WINS server.
There are two NetBIOS modes. The Datagram mode is the fastest mode, but
does not guarantee delivery. It uses a self-contained packet with send and
receive name, usually limited to 512 bytes. If the recipient device is not listen-
ing for messages, the datagram is lost. The Session mode establishes a connec-
tion until broken. It guarantees delivery of messages up to 64KB long.
Network
- A system that transmits any combination of voice, video, and/or
data between users.
Network Mask
- Also known as the “Subnet Mask.”
NIC
(
N
etwork
I
nterface
C
ard) - A board installed in a computer system, usu-
ally a PC, to provide network communication capabilities to and from that
computer system. Also called an adapter.
Node
- A network junction or connection point, typically a computer or work
station.
Notebook (PC)
- A notebook computer is a battery-powered personal comput-
er generally smaller than a briefcase that can easily be transported and conve-
niently used in temporary spaces such as on airplanes, in libraries, at temporary
offices, and at meetings. A notebook computer, sometimes called a laptop com-
puter, typically weighs less than five pounds and is three inches or less in thick-
ness.
OFDM
- Developed for wireless applications, Orthogonal Frequency Division
Multiplexing (OFDM) technology offers superior performance-increased data
rates and more reliable transmissions-than previous technologies, such as

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