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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.
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 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.
Download
- To receive a file transmitted over a network. In a communications
session, download means receive, upload means transmit.
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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
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 holding
place" but exists not so much to accelerate the speed of an activity as to sup-
port 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).
Category 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.
Default Gateway
- The routing device used to forward all traffic that is not
addressed to a station within the local subnet.
Denial of Service
- A protocol that directs the network to no longer respond to
requests that might arise as the result of a Denial of Service attack.
Denial of Service Attack
- An assault on a network that floods it with so many
additional requests that regular traffic is either slowed or completely interrupt-
ed.
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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 Web site 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.
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.
HPNA
(
H
ome
P
honeline
N
etworking
A
lliance) - An industry standard for
interconnecting computers within a home using existing telephone lines. Using
HPNA (also known as HomePNA), multiple computer users in a home can
share a single Internet connection, open or copy files from different computers,
share printers, and play multi-user computer games. The latest version, HPNA
2.0, allows data transmission at a rate of 10 Mbps over a home's standard tele-
phone line wiring system using the Ethernet CSMA/CD framing and transmis-
sion protocol. HPNA can be used without interrupting normal voice or fax
services. One user can talk on the phone at the same time other users are shar-
ing the same line to access the Web or share other computer resources.
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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.
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.
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.
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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).
IPX
(
I
nternetwork
P
acket E
X
change) - A NetWare communications protocol
used to route messages from one node to another. IPX packets include network
addresses and can be routed from one network to another.
ISP
(
I
nternet
S
ervice
P
rovider) - A company that provides individuals and
companies access to the Internet and other related services such as Web site
building and virtual hosting.
LAN
(
l
ocal
a
rea
n
etwork) - A group of computers and associated devices that
share a common communications line and typically share the resources of a
single processor or server within a small geographic area (for example, within
an office building).
MAC
(
M
edia
A
ccess
C
ontrol)
Address
- A unique number 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.
mIRC
- mIRC runs under Windows and provides a graphical interface for log-
ging onto IRC servers and listing, joining and leaving channels.
Multicasting
- Sending data to a group of nodes instead of a single destination.
Network
- A system that transmits any combination of voice, video and/or data
between users.
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 com-
puter 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, temporary
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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.
ICQ
- A conferencing program for the Internet that provides interactive chat,
e-mail and file transfer and can alert you when someone on your predefined list
has also come online.
IEEE
(The
I
nstitute of
E
lectrical and
E
lectronics
E
ngineers) - The IEEE
describes itself as "the world's largest technical professional society, promoting
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 several large societies in special areas, such as the
IEEE Computer Society.
IP
(
I
nternet
P
rotocol) - The method or protocol by which data is sent from one
computer to another on the Internet. It is a standard set of rules, procedures, or
conventions relating to the format and timing of data transmission between two
computers that they must accept and use to be able to understand each other.
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 packet across the Internet. When you
request an H
TM
L 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.
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-
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Server
- Any computer whose function in a network is to provide user access
to files, printing, communications, and other services.
Software
- Instructions for the computer. A series of instructions that performs
a particular task is called a "program." The two major categories of software are
"system software" and "application software." System software is made up of
control programs such as the operating system and database management sys-
tem (DBMS). Application software is any program that processes data for the
user.
A common misconception is that software is data. It is not. Software tells the
hardware how to process the data.
SPI
(
S
tateful
P
acket
I
nspection) - A firewall technology that monitors the state
of the transaction so that it can verify that the destination of an inbound pack-
et matches the source of a previous outbound request. It examines not just the
headers of the packet, but also the contents, to determine more about the pack-
et than just its source and destination information. It is called "stateful" because
verifies that the stated destination computer has previously requested the cur-
rent communication. In this way, it verifies that all communications are initiat-
ed by the recipient computer and are taking place only with sources that are
known and trusted from previous interactions. In addition to being a more rig-
orous inspection, stateful packet inspection closes off ports until connection to
the specific port is requested. This allows an added layer of protection from the
threat of port scanning.
SSID
(
S
ervice
S
et
ID
entifier) - A unique name shared among all points in a
wireless network. The SSID must be identical for each point in the wireless net-
work and is case-sensitive.
Static IP Address
- A permanent IP address that is assigned to a node in an IP
or a TCP/IP network.
STP
(
S
hielded
T
wisted
P
air) - Telephone wire that is wrapped in a metal
sheath to eliminate external interference.
Subnet Mask
- The method used for splitting IP networks into a series of sub-
groups, or subnets. The mask is a binary pattern that is matched up with the IP
address to turn part of the host ID address field into a field for subnets.
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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.
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.).
PC Card
- A credit-card sized removable module that contains memory, I/O,
or a hard disk.
Port
- A pathway into and out of the computer or a network device such as a
switch or router. For example, the serial and parallel ports on a personal com-
puter are external sockets for plugging in communications lines, modems and
printers.
PPTP
(
P
oint-to-
P
oint
T
unneling
P
rotocol) - A protocol which allows the Point
to Point Protocol (PPP) to be tunneled through an IP network. PPTP does not
specify any changes to the PPP protocol but rather describes a "tunneling serv-
ice" for carrying PPP (a tunneling service is any network service enabled by
tunneling protocols such as PPTP, L2F, L2TP, and IPSEC tunnel mode). One
example of a tunneling service is secure access from a remote small office net-
work to a headquarters corporate intranet via a Virtual Private Network (VPN)
that traverses the Internet. However, tunneling services are not restricted to cor-
porate environments and may also be used for personal (i.e., non-business)
applications.
RJ-11
(
R
egistered
J
ack-
11
) - A telephone connector that holds up to six wires.
The RJ-11 the common connector used to plug a telephone into a wall.
RJ-45
(
R
egistered
J
ack-
45
) - A connector similar to a telephone connector that
holds up to eight wires, used for connecting Ethernet devices.
Router
- Protocol-dependent device that connects subnetworks together.
Routers are useful in breaking down a very large network into smaller subnet-
works; they introduce longer delays and typically have much lower throughput
rates than bridges.
RTS
(
R
equest
T
o
S
end) - An RS-232 signal sent from the transmitting station
to the receiving station requesting permission to transmit.
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USB 1.1-compliant devices support data rates of 1.5Mbps (low-speed) and up
to 12Mbps (full-speed). USB 2.0-compliant devices are backward compatible
with earlier USB devices, and they support data rates of 1.5Mbps (low-speed),
12Mbps (full-speed), and up to 480Mbps (high-speed).
UTP
- Unshielded twisted pair is the most common kind of copper telephone
wiring. Twisted pair is the ordinary copper wire that connects home and many
business computers to the telephone company. To reduce crosstalk or electro-
magnetic induction between pairs of wires, two insulated copper wires are
twisted around each other. Each signal on twisted pair requires both wires.
Since some telephone sets or desktop locations require multiple connections,
twisted pair is sometimes installed in two or more pairs, all within a single
cable.
WAN
(
W
ide
A
rea
N
etwork)- A communications network that covers a rela-
tively large geographic area, consisting of two or more LANs.
Broadband com-
munication over the WAN is often through public networks such as the tele-
phone (DSL) or cable systems, or through leased lines or satellites.
In its most
basic definition, the Internet could be considered a WAN.
WEP
(
W
ired
E
quivalent
P
rivacy) - A data privacy mechanism based on a 64-
bit or 128-bit shared key algorithm, as described in the IEEE 802.11 standard.
WINIPCFG
- Configuration utility based on the Win32 API for querying,
defining and managing IP addresses within a network.
A commonly used util-
ity for configuring networks with static IP addresses.
WLAN
(
W
ireless
L
ocal
A
rea
N
etwork) - A group of computers and associat-
ed devices that communicate with each other wirelessly.
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Switch
- 1. A data switch connects computing devices to host computers,
allowing a large number of devices to share a limited number of ports. 2. A
device for making, breaking, or changing the connections in an electrical cir-
cuit.
TCP
(
T
ransmission
C
ontrol
P
rotocol) - A method (protocol) used along with
the IP (Internet Protocol) to send data in the form of message units (datagram)
between network devices over a LAN or WAN. While IP takes care of handling
the actual delivery of the data (routing), TCP takes care of keeping track of the
individual units of data (called packets) that a message is divided into for effi-
cient delivery over the network. TCP is known as a "connection oriented" pro-
tocol due to requiring the receiver of a packet to return an acknowledgment of
receipt to the sender of the packet resulting in transmission control.
TCP/IP
(
T
ransmission
C
ontrol
P
rotocol/
I
nternet
P
rotocol) - The basic com-
munication language or set of protocols for communications over a network
(developed specifically for the Internet).
TCP/IP defines a suite or group of
protocols and not only TCP and IP.
Throughput
- The amount of data moved successfully from one place to anoth-
er in a given time period.
TX Rate
- Transmission Rate.
Upgrade
- To replace existing software or firmware with a newer version.
Upload
- To transmit a file over a network. In a communications session,
upload means transmit, download means receive.
URL
(
U
niform
R
esource
L
ocator) - The address that defines the route to a file
on the Web or any other Internet facility. URLs are typed into the browser to
access Web pages, and URLs are embedded within the pages themselves to pro-
vide the hypertext links to other pages.
USB
(
U
niversal
S
erial
B
us)
- A "plug-and-play" interface between a comput-
er and peripherals, such as digital cameras, scanners, game controllers, speak-
ers, keyboards, portable data storage, or printers. With USB, you can add a new
peripheral to your computer without having to add an adapter card or powering
down the computer. USB also supports hot-swapping, the addition or removal
of devices while the computer is running.
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