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Computer science > Data transmission (Paper 1) > Flashcards

Data transmission (Paper 1) Flashcards

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1
Q

What is packet switching?

A

Where data is broken up into smaller chunks (Packets)
These packets are given a sequence number and sent on its way
Each packet takes a different route depending on the quickest route
Routers control the routes the packets take
The packets may arrive in any order. once the last packet has arrived, the sequence numbers are used to put them back into the correct order and the data is then reconstructed correctly

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2
Q

What is meant by the term IP address?

A

The IP (internet protocol) address is the unique identification number given to every device

It is a 32 bit binary address broken into 4 bytes

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3
Q

What are three things that a packet contains?

A

Header, payload and trailer

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4
Q

What is a packet header

A

The packet header contains the destination IP address, the packet number and the originating IP address. this is so that the packet can be reorganized into the correct order when it arrives.

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5
Q

What is the packet payload?

A

The payload is the actual chunk of data being transmitted

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6
Q

What is the packet trailer?

A

Has the data that indicates the end of the packet and a checksum for the destination to check it is transmitted correctly

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7
Q

What are the benefits of packet switching?

A

It is more efficient compared to a traditional telephone network

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8
Q

What is serial transmission?

A

Where data bits are transmitted one bit at a single time down a single cable

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9
Q

What are the advantages and disadvantages of serial transmission?

A

Advantages:
Lower interference
More reliable over long distances
Smaller and simpler meaning it is cheaper to produce

Disadvantages:
Lower transmission speeds

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10
Q

What is parallel transmission?

A

Where several bits of data are sent simultaneously along several wires

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11
Q

What type of way is a USB transmitted?

A

Serial

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12
Q

What are the advantages and disadvantages of parallel transmission?

A

Advantages:
Sends data faster
Can send multiple bits at the same time

Disadvantages:
Interference issues between wires (Crosstalk)
Data corruption can occur over longer distances
Data bits travel at different speeds causing them to arrive at different times (Skewing)

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13
Q

What is simplex transmission?

A

Where data travels in one single direction along a single cable

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14
Q

What is an example of simplex transmission?

A

USB (Universal serial bus)
Sending data from the computer to the monitor

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15
Q

What is duplex transmission?

A

Where data can travel in both directions simultaneously using two communication channels

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16
Q

What is half-duplex transmission?

A

Where data can travel in both directions along a single cable but NOT simultaneously

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17
Q

What is serial simplex transmission?

A

Serial simplex transmission is when data is sent in one direction one bit at a time along the singular wire. (E.g. keyboard)

18
Q

What is serial half duplex transmission?

A

Serial half-duplex transmission is where data is sent in both directions however at a single time along the singular wire. One bit at a time. (E.g. a printer)

19
Q

What is serial duplex transmission?

A

Serial duplex transmission is where data is sent in both directions along the singular wire at the same time. One bit at a time. (E.g. a video call)

20
Q

What is parallel simplex transmission?

A

Parallel simplex transmission is where data is sent in one direction along the many wires. Many bits at a time. (E.g. integrated circuits on a motherboard)

21
Q

What is parallel duplex transmission?

A

Parallel duplex is where data is sent in both directions at the same time along many wires. Many bits at a time. (E.g. integrated circuits on a motherboard)

22
Q

What is parallel half duplex transmission?

A

Parallel half duplex is where data is sent in both directions at a single time along the many wires. Many bits at a time (E.g. integrated circuits on a motherboard)

23
Q

What does USB stand for?

A

Universal serial bus

24
Q

What are the benefits of a USB?

A

.It automatically detects the hardware and installs drivers for users
.No external power is needed
.Power can be transferred down the cable
.Reliable (Stable)
.They are serial
.Do not suffer from crosstalk and skewing
.A universal standard that can be used in many different devices

25
Q

What are the disadvantages of a USB?

A

.They can be lost easily
.The data transfer speeds are not fast enough to use in internal devices like CPUs and hard drives
.They can only be 5 meters in length

26
Q

What is a parity bit check?

A

A parity bit is a check bit, which is added to a block of data for error detection purposes. It is used to validate the integrity of the data. The value of the parity bit is assigned either 0 or 1 that makes the number of 1s in the message block either even or odd depending upon the type of parity.

27
Q

What is a checksum?

A

A checksum is an additional method of checking for errors following the transmission of data. The checksum is calculated from the data to be transmitted and is sent along with the data block.

At the receiving end, the checksum is recalculated. If the sent value and the calculated value don’t match, then there is an error in the received data.

The computer will then send an error message and ask the sending computer to re-transmit the data

28
Q

What is an echo check?

A

An echo check is performed by asking the recipient computer to send back the exact copy of the data it has received.

That data is then compared with the data that was originally sent and if they match then the data is seemed to have arrived without error

29
Q

What is encryption?

A

Encryption is the process of encoding data so that it cannot be easily understood if it is discovered, stolen or intercepted

30
Q

What is the definition of plaintext?

A

The original message to be encrypted

31
Q

What is the definition of ciphertext?

A

The message to be encrypted

32
Q

What is the definition of encryption?

A

The process of converting plaintext into ciphertext

33
Q

What is a key?

A

A sequence of numbers often used to encrypt or decrypt. sometimes using a mathematical formula

34
Q

What is the definition of Encryption algorithm?

A

The formula for encrypting plaintext

35
Q

What is symmetric encryption?

A

Symmetric encryption uses the same pre-shared key to encode and decode data. This means that the key must also be transferred separately to the recipient so that they can decrypt it.

36
Q

What is Asymmetric encryption?

A

Asymmetric encryption uses two separate but related. A public key is shared with others and used by them to encrypt a message so it can only be deciphered by the intended recipient with their private key. A private key must never be shared.

37
Q

What is skewing?

A

.Each wire in a parallel cable has slightly different properties
.Signals therefore arrive at different times
.The receiver must wait until all lines are received until the next set of bits can be sent
.Parallel transmission needs to be over very short distances to reduce the problem

38
Q

What is crosstalk?

A

.Crosstalk may occur when a signal on one line creates a disturbance in another line (Electric static interference)
.This may cause a bit to be reversed from either a 1 to a 0 or a 0 to a 1 in a parallel line
.The longer the cable is, the more chance there is of crosstalk and skewing

39
Q

What is a router?

A

A device that enables data packets to be moved to different networks for example to join a LAN to a WAN

40
Q

What is an automatic repeat request (ARQ)?

A

Computers using ARQs will automatically send back a positive acknowledgment if a data packet is deemed correct or they will ask for the data to be resent if an error is detected

If no acknowledgement is returned within a certain time period then a timeout is registered and the sending computer resends the packet

This process repeats until the packet is received or until the ARQ limit is reached

41
Q

What is a check digit?

A

A form of validating data entry rather than detecting errors in transmission

It is an addition digit at the end of a string and other numbers

It is typically used in barcodes and ISBN numbers

A checkdigit is recalculated on data entry and if it matches the numbers are deemed to be in the correct order and the right space

Computer science (7 decks)

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