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Computing > Data transmission (paper 1) > Flashcards

Data transmission (paper 1) Flashcards

1
Q

define a data packet

A

a small part of data that is transmitted over a network

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2
Q

define a packer header

A

the part of the data packet that contains the IP addresses and inclueds the packet number

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3
Q

define packet trailer

A

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

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4
Q

what is a cyclic redundancy check (CRC)

A

an error check method in which all the 1-bits in the data packet payload are added and the otal is stored in the packet trailer

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5
Q

what is the payload

A

the actual data being carried in a data packet

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6
Q

what is a node

A

Stages in a network that can receive and transmit data packets

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7
Q

what is packet switching

A

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

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8
Q

what is a router

A

a device that enables data packets to be moved between different networks

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9
Q

what is real time streaming

A

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

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10
Q

what is hopping / hop number

A

a number in a packet header used to stop data packets that never reaches their destinataion from ‘clogging up’ the data paths

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11
Q

define simplex data

A

data that can be sent in one direction only

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12
Q

define half-duplex data

A

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

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13
Q

define full-duplex data

A

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

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14
Q

what is serial data transmission

A

sending data down one channel/wire one bit at a time at very high speeds

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15
Q

what is parallel data transmission

A

sending data down several channels/wires serveral bits at a time over short distances

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16
Q

what is skewed data

A

data that arrives at the destination with the bits no longer synchronised

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17
Q

what does a USB stand for

A

universal serial bus

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18
Q

what is a USB

A

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

19
Q

what is an IP address

A

a unique string of characters that identifies each computer using the Internet Protocol to communicate over a network

20
Q

what are the benefits of packet switching

A
  • no need to tie up a single connection line
  • can easily overcome failed lines by re-reouting packets
21
Q

descirbe the process of packet switching

A
  • data is broken donw into packets
  • each packet is given a sequence number and sent
  • each packet may take a different route depending on the quickest route in the moment
  • routers control the route the packet takes
  • packets may arrive out of order
  • the sequence numbers put them back into order
22
Q

what are the benefits of serial data transmission

A
  • lower interference
  • more reliable over longer distances
  • smaller, simpler and cheaper connections to produce
23
Q

what are the negatives of serial data transmission

A
  • lower transmission speeds
24
Q

what are the benefits of parallel data transmission

A
  • very fast data transfer
  • can send data in both directions at the same time
25
Q

what are the negatives of parallel data transmission

A
  • interference issues between wires
  • data corruption can occur over longer distances
  • suffer from skewing: data bits travelling parallel to each other can move at different speeds causing them to arrive out of sync
26
Q

what types of parity may a computer use

A
  • even
  • odd
27
Q

how does a parity check work

A
  • Checks a byte of data
  • Check is performed when data is received
  • A parity bit is added (to the parity byte)
  • Counts number of 1’s to see if 1’s are even or odd
  • Can be even or odd
  • If parity is incorrect, error is detected
28
Q

when is a parity block check used

A

when sending multiple bytes in one transmission block

29
Q

what is a checksum

A

an additional method of checking for errors following the transmission of data

30
Q

explain a check digit

A
  • A digit that is calculated from the data, uses modulo to calculate digit
  • It is added to the data
  • Digit is recalculated when data is entered
  • Digits are compared to check for error
31
Q

explain automatic repeat request

A
  • Uses acknowledgement and time-out
  • Error control protocol
  • Check if error is detected by e.g. parity check, check sum
  • If error detected, request is sent to resend data
  • Resend request is repeated till data is sent correctly
  • Send acknowledgement that data is received
  • If acknowledgement not received in set time data is resent
32
Q

explain a checksum

A
  • A value is calculated from the data
  • It is transmitted with the data
  • Value is recalculated after transmission
  • Values are compared after transmission to check for error
33
Q

why are codes used

A

to prevent interception of messages

34
Q

what is plaintext

A

the original message to be encrypted

35
Q

what is ciphertext

A

the encrypted message

36
Q

what is symmetric encryption

A

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

37
Q

what is asymmetric encryption

A

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

38
Q

what are the two types of encryption

A
  • symmetric
  • asymmetric
39
Q

what is acknowledgement

A

a message sent to the receiver indicating that data has been received

40
Q

what is an eavsdropper

A

another name for a hacker who intercepts data being transmitted one a wored or wireless connection

41
Q

what is an encryption algorithm

A

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

42
Q

what is a public key

A

a type of encryption key that is known to all users

43
Q

what is a private key

A

a type of encyrption key which is known only to the single coputer/user

44
Q

what is a quantum computer

A

a computer which can preform very fast calculations, based on probability rather than simple 1 or 0 values

Computing (8 decks)

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