Access Point A device that allows wireless-equipped computers and ...

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21 Νοε 2013 (πριν από 3 χρόνια και 6 μήνες)

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Access Point

A device that allows wireless
-
equipped computers and other devices to communicate

with a wired network. Also used to expand the range of a wireless network.

Ad
-
hoc

A group of wireless devices communicating directly with each other
(peer
-
to
-
peer)

without the use of an access point.

Amplifier

A device used to boost the strength of an electronic or optical signal, which

is weakened (attenuated) as it passes through the transport network. Amplifiers

add gain to the signal by an amount e
qual to the loss in the previous section

of the network since last amplification.

Asymmetric Digital Subscriber Line (ADSL)

A new technology that allows more data to be sent over existing copper telephone

lines. ADSL supports data rates of from 1.5 to 9 Mb
ps when receiving data (known

as the downstream rate) and from 16 to 640 Kbps when sending data (known as

the upstream rate).

Asynchronous Transfer Mode (ATM)

A method of sending audio, visual and computer data at the same time over one

high
-
speed digital
line.

Backbone

The part of a network that connects most of the systems and networks together,

and handles the most data.

Beacon Interval

Data transmitted on your wireless network that keeps the network synchronized.

Bridge

A device that connects two differ
ent kinds of local networks, such as a wireless

network to a wired Ethernet network.

Broadband

A transmission channel usually carrying a tremendous amount of information.

A communications channel with a bandwidth sufficiently large to carry voice,

data and

video on a signal channel. Any voice communications channel having

a bandwidth greater than a voice
-
grade channel.

Broadcast storm

An incorrect packet broadcast onto a network that causes multiple hosts to

respond all at once, typically with equally incor
rect packets which causes the

storm to grow exponentially in severity.

Buffer

A shared or assigned memory area that is used to support and coordinate different

computing and networking activities so one isn't held up by the other.

Burst Mode

A way of doing

data transmission, usually faster than normal transmission mode,

in which a continuous block is transferred between main memory and an
input/output

device without interruption until the transfer has been completed. Characteristically,

burst mode is sustai
nable for only limited periods of time under special conditions.

Cable Modem

A device that connects a computer to the cable television network, which in

turn connects to the Internet.

Checksum

A computed value which is dependent upon the contents of a
packet. This value

is sent along with the packet when it is transmitted. The receiving system computes

a new checksum based upon the received data and compares this value with the

one sent with th
e

packet. If the two values are the same, the receiver has a

high degree of confidence that the data was received correctly.

Circuit switching

A communications paradigm in which a dedicated communication path is
established

between two hosts, and on which all packets travel. The telephone system is

an example of a
circuit switched network.

Client

A computer system or process that requests a service of another computer system

or process. A workstation requesting the contents of a file from a file server

is a client of the file server.

Compression

Algorithm that minim
izes the redundancy in the signal to be transmitted.

Congestion

Congestion occurs when the offered load exceeds the capacity of a data
communication

path.

Connection Oriented

The data communication method in which communication proceeds through three

well
-
defined phases: connection establishment, data transfer, connection release.

TCP is a connection
-
oriented protocol.

Cryptography

The process of concealing the contents of a message from all except those who

know the key. Cryptography is used to protect e
-
m
ail messages, credit card
information,

and corporate data. As the Internet and other forms of electronic communication

become more prevalent, electronic security is also becoming increasingly important.

Database

A collection of data that is organized so th
at its contents can easily be accessed,

managed, and updated

Default Gateway

A device that forwards Internet traffic from your local area network.

Default route

A routing table entry which is used to direct packets addressed to networks

not explicitly list
ed in the routing table.

DHCP (Dynamic Host Configuration Protocol)

A protocol that lets one device on a local network, known as a DHCP server,

assign temporary IP addresses to the other network devices, typically computers.

DNS (Domain Name Server)

The IP

address of your ISP's server, which translates the names of websites

into IP addresses.

Encapsulation

The technique used by layered protocols in which a layer adds header information

to the protocol data unit (PDU) from the layer above.

Encryption

Encryption is the manipulation of data to prevent accurate interpretation by

all but those for whom the data is intended. There are many types of data encryption,

and they are the basis of network security.

Ethernet

An IEEE standard network protocol that s
pecifies how data is placed on and

retrieved from a common transmission medium.

Fault Tolerance

The ability of a system to respond gracefully to an unexpected hardware or

software failure. There are many levels of fault tolerance, the lowest being

the abil
ity to continue operation in the event of a power failure.

Firewall

A firewall is any of security schemes that prevent unauthorized users from

gaining access to a computer network or that monitor transfers of information

to and from the network.

FTP (File
Transfer Protocol)

A standard protocol for sending files between computers over a TCP/IP network

and the Internet. FTP is usually the name of the program the user invokes to

execute the protocol.

Fragment

A piece of a packet. When a router is forwarding an

IP packet to a network

that has a maximum packet size smaller than the packet size, it is forced to

break up that packet into multiple fragments. These fragments will be reassembled

by the IP layer at the destination host.

Full Duplex

The ability of a net
working device to receive and transmit data simultaneously.

Full duplex is sometimes called "Echo On" by some communications programs.

Gateway

A device that interconnects networks with different, incompatible communications

protocols. The term "router" is
now used in place of the original

definition of "gateway". Currently, a gateway is a communications

device/program which passes data between networks having similar functions but

dissimilar implementations. This should not be confused with a protocol conve
rter.

By this definition, a router is a layer 3 (network layer) gateway, and a mail

gateway is a layer 7 (application layer) gateway.

Half Duplex

Data transmission that can occur in two directions over a single line, but

only one direction at a time.

Hacke
r

A slang term for a computer enthusiast. Also refers to individuals who gain

unauthorized access to computer systems for the purpose of stealing and corrupting

data.

Host

A computer that allows users to communicate with other host computers on a

network.
Individual users communicate by using application programs, such as

electronic mail, Telnet and FTP.

Hub

A device connected to several other devices. In ARCnet, a hub is used to connect

several computers together. In a message handling service, a hub is
used for

the transfer of messages across the network.

HTTP (HyperText Transport Protocol)

The communications protocol used to connect to servers on the World Wide Web.

IEEE (The Institute of Electrical and Electronics Engineers)

An independent institute th
at develops networking standards.

ISP (Internet Service Provider)

A company that provides access to the Internet.

Latency

The amount of time it takes a packet to travel from source to destination.

Together, latency and bandwidth define the speed and capaci
ty of a network.

MAC (Media Access Control) Address

A MAC address is the hardware address of a device connected to a shared network

medium.

Medium

The material used to support the transmission of data. This can be copper wire,

coaxial cable, optical fib
er
,

or electromagnetic wave (as in microwave).

Multicasting

Sending data to a group of destinations at once. The ability of one network

node to send identical data to a number of end servers on the multicast backbone.

For large amounts of data, IP multicastin
g is more efficient than normal Internet

transmissions because the server can broadcast a message to multiple recipients

simultaneously.

NAT (Network Address Translation)

NAT technology translates IP addresses of the local area network to a different

IP ad
dress for the Internet.

Node

A network junction or connection point, typically a computer or work station.

Optical Fiber

Thin filaments of glass through which light beams are transmitted. Enormous

capacity, low
-
cost, low
-
power consumption, small space, lig
htweight, insensitivity

to electromagnetic interference characterize this transport media.

Packet

A unit of data transmitted over a network.

Ping (Packet INternet Groper)

An Internet utility used to determine whether a particular IP address is online.

POP3

(Post Office Protocol 3)

A standard protocol used to retrieve e
-
mail stored on a mail server.

Port

The connection point on a computer or networking device used for plugging in

a cable or an adapter.

Repeater

Equipment that receives a low
-
power signal, pos
sibly converting it from

light to electrical form, amplifying it or retiming and reconstructing it for

transmission. It may need to be reconverted to light for retransmission.

RJ
-
45 (Registered Jack
-
45)

An Ethernet connector that holds up to eight wires.

R
oaming

The ability to take a wireless device from one access point's range to another

without losing the connection.

Router

A networking device that connects multiple networks together, such as a local

network and the Internet.

SMTP (Simple Mail Transfer P
rotocol)

The standard e
-
mail protocol on the Internet.

Static IP Address

A fixed address assigned to a computer or device that is connected to a network.

Switch

1. A device that is the central point of connection for computers and other

devices in a networ
k, so data can be shared at full transmission speeds.

2. A device for making, breaking, or changing the connections in an electrical

circuit.

TCP (Transmission Control Protocol)

A network protocol for transmitting data that requires acknowledgement from

th
e recipient of data sent.

TCP/IP (Transmission Control Protocol/Internet Protocol)

A network protocol for transmitting data that requires acknowledgement from

the recipient of data sent.

Telnet

A user command and TCP/IP protocol used for accessing remote
PCs.

Throughput

The amount of data moved successfully from one node to another in a given time

period.

Upgrade

To replace existing software or firmware with a newer version.

Upload

To transmit a file over a network.

Voice over IP (VoIP)

VoIP is voice
communications transmitted over the Internet.

WLAN (Wireless Local Area Network)

A group of computers and associated devices that communicate with each other

wirelessly.