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Computer science A level > Networks and the internet > Flashcards

Networks and the internet Flashcards

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1
Q

what is a network topology

A

the way a network and its connected devices are connected

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2
Q

what does CSMA/CA stand for

A

Carrier Sense Multiple Access with collision avoidance

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3
Q

what does data travel over when we use wifi

A
  • a frequency (channel)
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4
Q

implications of using wireless networks

A
  • as communication is done in an open space, it’s less secure
  • transmission speed is lower because of traffic
  • has a limited amount of bandwidth for communication and breaches of network security
  • can be easily hacked
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5
Q

channels have a frequency range of….

A

22MHZ

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6
Q

describe the CSMA/CA without RTS/CTS

A
  • if a device is ready to send some data, it starts and assembles the packet of data it wants to send
  • asks if the channel idle
  • if yes, data is transmitted
  • if no, device waits a random amount of time and checks if the channel is idle again
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7
Q

describe the CSMA/CA with RTS CTS

A
  • transmitting device checks for traffic
  • if another transmission is in progress, the transmitter continues to wait
  • if channel is idle, transmitter would send a request to send
  • Receiver/WAP responds with a clear to send signal
  • if CTS not received, transmitter would wait a random amount of time before sending the RTS
  • when CTS is received, the transmitter begins transmitting data
  • receiver sends acknowledgment if all data is received
  • if no acknowledgment is sent, data is resent
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8
Q

the hidden node problem and how to fix it

A
  • node a can see the WAP because it’s in range, node b can also see WAP
  • node a cant see node b because they are out of range with each other
  • if both nodes try to transmit data wirelessly, using CSMA/CA without RTS will result in data collisions
  • by adding an RTS/CTS, node A doesn’t need to make any assumptions abt how many nodes there are etc, it just adds an extra layer of protection, and the WAP checks everything
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9
Q

what is the Wireless AccessPoint

A
  • a hardware device that allows wireless devices to connect to a wired network using Wi-Fi or related standards.
  • it bridges wireless and wired networks,
  • enhance network connectivity by increasing the range and coverage area of the network
  • provide flexibility in network setup and expansion, allowing for easy addition of new devices
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10
Q

what is a wireless router

A

a networking device that forwards data packets between computer networks, eg over the internet

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11
Q

what is a wireless network adapter/interface

A
  • a hardware device that enables a computer or other device to connect to a wireless network
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12
Q

what does a WirelesssAccessPoint require access to

A

it requires a connection to the router, and the router requires a connection to a modem

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13
Q

what is a modem

A

a modulator demodulator - a computer hardware which converts data from a digital format into a format suitable for an analog transmission medium such as a telephone or radio (a DAC)

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14
Q

features of service set IDentifiers (SSIDs)

A
  • identifies each network by a unique name
  • must be used by all devices on that network
  • can be set manually or automatically
  • can be hidden to make it harder to detect
  • can be set to broadcast a range of wireless devices in range of an access point
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15
Q

what do WPA and WPA2 do

A
  • WPA and WPA2 utilize a form of authentication known as PSK
  • Users must enter a password to authenticate themselves to the network.
  • WPA and WPA2 dynamically generate and manage encryption keys to enhance security. these keys are periodically changed
  • they use MAC (Media Access Control) address filtering, which allows or denies network access based on the unique hardware address of a device.
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16
Q

what is serial data transmission

A

a type of data transmission where bits are sent via an interface one at a time over a single wire from the source to the destination

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17
Q

what is parallel data transmission

A

where multiple bits are sent simultaneously over a number of parallel wires

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18
Q

disadvantages of parallel data transmission

A

each individual wire has different properties, there is a possibility that bits can travel at different speeds over each wires, creating the problem of skew

  • parallel transmission only works over short distances
  • parallel transmission can suffer from crosstalk and timing issues since each bit travels on a different wire, potentially interfering with one another and reducing overall efficiency
19
Q

advantages of serial transmission over parallel

A
  • large reduction in size and complexity of connectors in serial transmission leads to lower costs
  • crosstalk will not occur, as all bits are sent on the same wire, reducing interference and allowing for longer distances., may result in corrupted words
  • Serial transmission is cheaper; due to needing fewer wires / less complex hardware;
  • skew wont occur as bits are sent one at a time
  • serial links are more reliable over longer distances than parallel
  • signal frequency can be much higher with serial because of the lack of interference at higher frequencies, resulting in a higher net data tranfer rate, even though less data is transmitted per cycle
20
Q

what is bit rate

A

the number of bits that can be sent in a given unit of time

21
Q

what is baud rate

A

the number of signal changes in a given period of time/in a second

22
Q

baseband mode

A

in baseband mode, only two voltages are used

23
Q

bit rate equation

A

bit rate of channel = baud rate x n of bits per signal

24
Q

what is bandwith

A
  • The range of frequencies that can be transmitted across a network connection;
  • shared between all active users, so too many users can cause performance to decrease
25
Q

what is latency

A
  • the time delay of data to travel from source to destination
26
Q

what is synchronous transmission

A

where data is transferred at regular intervals that are timed by a clock signal

27
Q

advantages of synchronous transmission

A

timing using a clock signal allows for a constant and reliable transmission for time sensitive data

28
Q

examples of time sensitive data

A

real time video or voice

29
Q

what is asynchronous transmission

A
  • when the receiver and transmitter are not synchronised
  • transmission of data without use of external clock signal
    -one byte is sent at a time, with each character being preceded by a start bit and followed by a stop bit
30
Q

examples of things that use synchronous transmission

A

CPU - the clock emits a signal at regular intervals and transmissions along the address, data and control bus start on a clock signal, which is shared by both receiver and sender

31
Q

Purpose of the start and stop bit

A
  • The start bit alerts and synchronizes the receiver to the start of a data packet
  • The stop bit ensures clear separation between data packets, giving the receiver time to reset and get ready for the next packet.
32
Q

what are protocol

A

a set of rules which govern communication

33
Q

advantages of disabling SSIDs

A

prevents the network from appearing in the list of available networks, making it less visible to potential attackers

34
Q

advantages of mac addressing

A

mac address whitelisting means only approved devices can join he network

35
Q

what are SSIDs

A

they identify the network

36
Q

things that affect network performance

A

topology
- bandwidth, higher bandwidth increases performance
- choice of hardware
- wired or wireless, wired are ussually faster and more reliable

37
Q

what is a wide area network

A

a collection of computers connected over a large geographical area, like the internet

38
Q

advantages and disadvantages of asynchronous transmission

A
  • Easier and cheaper to implement because it doesn’t require synchronization between the sender and receiver.
  • Ideal for low-speed communication and can handle irregular data transmission rates

DISADVANTAGES:
- Additional start and stop bits increase the amount of data transmitted, reducing efficiency.
- Generally slower due to the need to process each byte individually and add control bits.

39
Q

advantages and disadvantages of synchronous transmission

A
  • No start and stop bits, so it is more efficient for transmitting large amounts of data
  • Typically faster because data is sent in a continuous stream.

DISADVANTAGES -
- Requires synchronization between the sender and receiver, making it more complex and expensive to implement
- Initial setup and synchronization can take time, making it less suitable for small amounts of data or sporadic transmissions

40
Q

relationship between bit rate and bandwidth

A

directly proportional

41
Q

what is WIFI

A
  • A wireless local area network that is based on international standards.
  • Used to enable devices to connect to a network wirelessly
42
Q

advantages of SSIDS

A
  • ## Using unique SSIDs reduces the likelihood of connecting to the wrong network accidentally and helps prevent unauthorized access
43
Q

why is protocol important

A

to ensure that equipment from different suppliers can communicate

44
Q

items that are covered by communication protocol

A

Physical connections, cabling, mode of transmission, speed, data format, error correction.

Computer science A level (28 decks)

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