iGCSE Computer Science Chapter 2

bandwidth

The maximum amount of data transmitted over an internet connection in a given amount of time.

full-duplex

a transmission method where data is transmitted in both directions at the same time.

half-duplex

a transmission method where is transmitted in both directions, but only one direction at a time.

internet

a very large global network that allows users to access the world wide web.

latency

Latency is the time it takes for data to be transferred between its original source and its destination, measured in milliseconds. Internet latency and network latency affect satellite internet connections, cable internet connections, as well as some WiFi connections.

packet header

a section of a packet of data that contains information about the contents of the packet and its destination.

packet switching

a method of transmitting data packets across a network. Each data packet is able to take an individual pathway across the network.

packet

a small unit of data.

simplex

a transmission method where data is transmitted in a single direction only.

USB cable

a type of transmission media that uses the USB method to transmit data.

USB connection

a collective name for using a USB cable plugged into a USB port to transfer data from one device to another.

USB device

the name of a device that plugs into a USB port on a computer.

USB port

a socket that is a part of a device or computer that enables you to insert a USB cable.

USB

an industry standard that is used to transmit data.

automatic repeat request (ARQ)

a type of error detection method that uses acknowledgement and timeout to see if data has arrived correctly after transmission.

check digit

a type of error detection method that is used for data entry. A calculation is performed on the data entered to create a value. Check digit values are compared to see if the data entered is correct.

checksum

a type of error detection method that performs a calculation on the data to create a checksum value. Checksum values arc compared after transmission to see if they match.

echo check

a type of error detection method that sends a copy of the transmitted data back to the sender to be compared with the original data sent.

parity check

a type of error detection method that adds an additional bit to each byte to create an odd or even sum.

asymmetric

a type of encryption that uses two different keys to encrypt and decrypt data.

cipher text

the name given to data after transmission.

encryption

a method of securing data for storage or transmission that scrambles it and makes it meaningless, encryption key

plain text

the name given to data before encryption.

symmetric

a type of encryption that uses the same key to encrypt and decrypt data.

payload

the actual data that the user is sending to the receiver.

trailer

a section of a packet of data that contains information about any error checking methods that may be used.

ethernet

a system for connecting a number of devices to form a local area network. (Using cables)

router

a network component that examines a data packet to obtain its destination address and then forwards the packet to this address.

network

computers and devices that are joined together using cables or wireless technology.

internet protocol (IP) address

the unique address that is given to a device when it is connected to a network.

skew

Skew is a disadvantage of parallel transmission. Skew is caused by the fact that each wire in a parallel transmission setup will have slightly different properties. This will mean that each signal will travel at a slightly different speed therefore arriving at their destination at different times.

Public Key

It is part of asymmetric cryptography. This is the key that is shared. If you encode with the public key only the private key can decode. If someone encodes with a private key anybody with the public key can decode.

private key

This is the key that you should share with no one. If you encode with a private key anybody with the public key can decode. Your private key can be used to decode something encoded with your public key. (Part of asymmetric cryptography)