Chapter 2 Definitions Flashcards
Define data packet
A small part of a message/data that is transmitted over a network; after transmission all the data packets are reassembled to form the original message/data
Define packet header
The part of the data packet that contains the IP addresses of the sender and receiver, and includes the packet number which allows reassembly of the data packets
Define cyclic redundancy check (CRC)
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 receiving station
Define payload
The actual data being carried in a data packet
Define node
Stages in a network that can receive and transmit data packets; routers are nodes in communication networks
Define packet switching
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
Define router
A device that enables data packets to be moved between different networks
Define real time streaming
The transmission of data over a network for live events where the data is sent as soon as it is received or generated
Define hopping/hop number
A number in a data packet header used to stop data packets that never reach their destination from ‘clogging up’ the data paths/routes
Define simplex
Data that can be sent on one direction only
Define half-duplex
Data that can be sent in both directions but not at the same time
Define full-duplex
Data that can be sent in both directions at the same time (simultaneously)
Define serial data transmission
Sending data down one channel at a time
Define parallel data transmission
Sending data down several channels/wires several bits at a time
Define skewed (data)
Data that arrives at the destination with the bits no longer synchronised
Define universal serial bus (USB)
A type of serial data transmission which has become the industry standard for connecting computers to devices via a USB port
Define parity check
A method used to check if data has been transferred correctly; it makes use of even parity or odd parity
Define parity bit
A bit 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
Define parity block
A horizontal and vertical parity check on a block of data being transmitted
Define parity byte
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
Define checksum
A verification method used to check if data transferred has been altered or corrupted; calculated from the block of data of data being sent; the checksum value is sent after each data block
Define automatic repeat request (ARQ)
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
Define acknowledgement
A message sent to the receiver indicating that data has been received correctly (used in the ARQ error detection method)
Define timeout
The time interval allowed to elapse before an acknowledgement is received (in the ARQ error detection method)
Define echo check
A method used to check if data has been transferred correctly; data is sent to a receiver and then immediately sent back to the sender; the sender then checks if the received data matches the sent data
Define check digit
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
Define eavesdropper
Another name for a hacker who intercepts data being transmitted on a
wired or wireless network
Define encryption
The process of making data meaningless using encryption keys; without the correct decryption key the data cannot be decoded (unscrambled)
Define plaintext
The original text/message before it is put through an encryption algorithm
Define ciphertext
Encrypted data that is the result of putting a plaintext message through an encryption algorithm
Define encryption algorithm
A complex piece of software that takes plaintext and generates an
encrypted string known as ciphertext
Define symmetric encryption
A type of encryption in which the same encryption key is used both
to encrypt and decrypt a message
Define asymmetric encryption
A type of encryption that uses public keys and private keys to
ensure data is secure
Define public key
A type of encryption key that is known to all users
Define private key
A type of encryption key which is known only to the single computer/user
Define quantum computer
A computer that can perform very fast calculations; it can perform
calculations that are based on probability rather than simple 0 or 1 values; this gives a quantum computer the potential to process considerably more data than existing computers
