2. Data transmittion

Question 1

Data packet

Answer 1

a small part of a message/data that is transmitted over a network; after transmitton all the data packets are reassembled to form the orignal message/data

Question 2

Packet header

Answer 2

the part of the data packet that contains the IP addresses of the sender and receiver, and incudes the packet number which allows reassembly of the data packets

Question 3

Packet trailer

Answer 3

the part of a data packet that indicates the end of the data packet and cyclic redundancy check error check

Question 4

Cyclic redundancy check (CRC)

Answer 4

an error checking method in which all the 1-bits in the data packet payload are added and the total is stored in the packet trailer; the same calculation is repeated at the receivng station

Question 5

Payload

Answer 5

the actual data being carried in a data packet

Question 6

Node

Answer 6

stages in a network that can receive and transmit data packets; routers are nodes in communication networks

Question 7

Packet switching

Answer 7

a method of transmission in which a message is broken into many data packets which can then be sent along pathways independently of each other

Question 8

Router

Answer 8

a device that enables data packets to be moved between different networkd, for example to join a LAN to a WAN

Question 9

Real time streaming

Answer 9

the transmission data over a network for live events where the data is sent as soon as it is received or generated

Question 10

Hopping/hop number

Answer 10

a number in a data packet header used to stop data packets that never reach their destination from ‘clogging up’ the data paths/routes

Question 11

Simplex

Answer 11

data that can only be sen in one direction

Question 12

Half-duplex

Answer 12

data that can be sent in both directions but not at the same time

Question 13

Full-duplex

Answer 13

data that can be sent in both directions at the same time (simultaneously)

Question 14

Serial data transmission

Answer 14

sending data down one channel/wire one bit at a time

Question 15

Parallel data transmission

Answer 15

sending data down several channels/wiresseveral bits at a time (usually 1 byte)

Question 16

Skewed (data)

Answer 16

data that arrives at the destination with bits no longer synchronised

Question 17

Universal serial bus (USB)

Answer 17

a type of serial data transmission which has become the industry standard for connecnting computers to devices via a USB port

Question 18

Parity check

Answer 18

a method used to check if data has been transferred correctly; it makes use of even parity (an even number of 1-bits) or odd parity (an odd number of 1-bits)

Question 19

Parity bit

Answer 19

a bit (either 0 or 1) added to a byte of data in. the most significant bit position; this ensures that the byte follows the correct even parity or odd parity protocol

Question 20

Parity block

Answer 20

a horizontal and vertical parity check on a block of data being transmitted

Question 21

Parity byte

Answer 21

an extra byte of data sent at the end of a parity block; it is composed of the parity bits generated from a vertical parity check of the data block

Question 22

Checksum

Answer 22

a verification method used to check if data transferred has been altered or corrupted; calculated from the block of data being sent; the checksum value is sent after each data block

Question 23

Automatic repeat request (ARQ)

Answer 23

a method of checking transmitted data for errors; it makes use of acknowledgement and timeout to automatically request re-sending of data if the time interval before positive acknowledgement is too long

Question 24

Acknowledgement

Answer 24

a message sent to the receiver indicating that data has been received correctly (used in the ARQ error detection metod)

Question 25

Echo check

Answer 25

a method used to check if data has been transferred correctly; data is sent to receiver and then immediately sent back to the sender; the sender then checks if the received data matches the transferred data

Question 26

Check digit

Answer 26

an additional digit appended to a number to check if the entered number is error-free; check digit is a data entry check and not a data transmission check

Question 27

Eavesdropper

Answer 27

another name for a hacker who intercepts data being transmitted on a wired or wireless network

Question 28

encryption

Answer 28

the process of making data meaningless using encryption keys; without the correct decryption key the data cannot be decoded (unscambled)

Question 29

Plaintext

Answer 29

the original text/message before it is put through and encryption algorithm

Question 30

Ciphertext

Answer 30

encrypted data that is the result of putting a plaintext message through an encryption algorithm

Question 31

Encryption algorithm

Answer 31

a complex piece of software that takes plaintext and generates an encrypted string known as ciphertext

Question 32

Symmertic encryption

Answer 32

a type of encryption in which the same encryption key is used both to encrypt and decrypt a message

Question 33

Asymmetric encryption

Answer 33

a type of encryption that uses public keys and private keys to ensure data is secure

Question 34

Public key

Answer 34

a type of encryption key that is known to all users

Question 35

Private key

Answer 35

a type of encryption key which is known only to the single computer/user

Question 36

Quantum computer

Answer 36

a computer that can perform very fast calulations; it can perform calculations that based on probability rather than simple 0 or 1values; this gives a quantum computer the potential to process considerably more data than existing computers