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A-level Computer Science > SLR 21 - networks and the internet > Flashcards

SLR 21 - networks and the internet Flashcards

1
Q

What is a topology ?

A

Refers to the structure of a network

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2
Q

What are the two types of topology?

A
  • physical and logical
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3
Q

What is a physical network topology?

A
  • refers to the actual architecture of a network
  • the two types are star and bus
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4
Q

How is a physical star topology connected?

A
  • each client in a network has its own direct connection to the central hub
  • the hub receives packets from all clients and is responsible for correctly delivering them to recipients
  • a serve can be connected in the same way the clients are connected to the central hub
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5
Q

What are the advantages of a physical star topology?

A
  • packets are sent through a direct connected to recipient (other clients can’t see them)
  • its easy to add and remove clients from a network
  • collisions don’t occur because each cable communicates for one device
  • the rest of the network wont be affected if one cable fails
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6
Q

What are the disadvantages a physical star topology?

A
  • if the central hub fail, all communication over the network is stopped
  • expensive to install because of the amount of cables
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7
Q

What is a physical bus topology?

A
  • clients are connected to a single main cable called the backbone
  • a terminator is placed at either end of the backbone
  • a server could be connected to the backbone like a star another computer
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8
Q

What are the advantages of a physical bus topology?

A
  • there is no central hub, so network failure is less likely
  • its less expensive as less cabling is required
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9
Q

What are the disadvantages of a physical bus topology?

A
  • packets sent through the shared backbone (clients can see all the packets not intended for them)
  • there is a risk of collisions
  • the entire network becomes unusable
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10
Q

What is a logical network topology?

A

a logical network topology refers to the flow of data packets in a network

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11
Q

What is the process of a logical bus versus a logical star?

A
  • logical bus delivers packets to all clients
  • logical star delivers packets only to their recipient
  • stars can act like buses and vice versa e.g., a set up is physically a star but sends data to every device in the network
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12
Q

What is a host?

A
  • A device on a network that provides services
  • the server and the clients can be hosts
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13
Q

What is a client server network?

A
  • servers are connected in the same way as clients but are more powerful
  • clients request services from the server and they respond to the client by providing a service
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14
Q

Why would schools use a client server?

A
  • it allows for central management
  • it can improve security
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15
Q

How does a peer to peer network work?

A
  • services are provided by the clients themselves
  • every client has an equal status
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16
Q

Disadvantage of peer to peer:

A
  • all clients providing service must be running for the network to be fully operational
  • e.g., client managing data storage breaks and no one can pen their file
17
Q

Advantage of peer to peer:

A
  • is more cost effective as there is no need for a powerful server
  • much easier to set up and maintain
18
Q

What do large file sharing networks use

A
  • use peer-to-peer networking to provide high
    performance services without the requirement for a server
19
Q

What is WiFi?

A

it is a local area wireless technology that connected devices together using WAPs, that is based on international standards

20
Q

How does WiFi work?

A

any wireless device meets specific standards allowing interoperability and backward compatibility

21
Q

What was formed in 1999?

A

the WIFI Alliance was formed to establish international standards for interoperability and backward compatibility

22
Q

What does connecting to a wireless network require? where can this be found?

A
  • a wireless network adapter
  • most computers come with integrated n the mother board
23
Q

What is a station?

A

the combination of a computer and the interface controller

24
Q

what do stations share?

A

a single radio frequency communication channel, which they tune to the frequency of in order to pick up transmissions

25
Q

What receives transmissions ?

A

all the stations within the range of the wireless access point

26
Q

How does the WAP connect to the internet?

A

WAP usually connects to a router, but it can also be integral part of the router

27
Q

What do you use to secure a wireless network?

A
  • WPA (Wi-Fi Protected Access)
  • Wi-Fi Protected Access II (WPA2)
28
Q

What is WPA2?

A
  • it is built into wireless network interface cards
  • it provides strong encryption of data transmissions
  • it has a new 128-bit key being generated for each packet sent
29
Q

What does SSID stand for and what is it?

A
  • SSID = Service Set Identification (the informal name for a network)
  • e.g., Home223
  • the purpose is to name the network so you can identify it as your computer will be in range of several networks
30
Q

What an you do to the SSID?

A

You can disable the broadcast of your SSID from others looking to connect to a named network

31
Q

What is a whitelist?

A
  • uses MAC addresses to control who is allowed on networks
  • addresses are assigned to every wireless device by their manufacturer and are unique to that device
  • blacklists ca also be used to block specific devices from connecting to a network
32
Q

What is CSMA/CA?

A
  • (Carrier Sense Multiple Access/Collision Avoidance) is a protocol for the carrier transmission in wireless local are networks
33
Q

What is CSMA/CA used for?

A

it avoids collisions in data networks caused when multiple devices communicate simultaneously

34
Q

What does a device do when its ready to transmit?

A
  • it listens to its communication channel to check whether it is idle
  • if so, the data is transmitted
  • if not, the device waits for a random period of time before checking the channel again
35
Q

What can be used to increase the time period a device will wait between each channel check?

A

an exponential backoff algorithm

36
Q

What is a hidden node?

A

it’s when a node can communicate with a (WAP), but cannot directly communicate with other nodes that are communicating with it - they cant see each other.

37
Q

What protocol deal with hidden nodes? how.

A
  • Request to send/clear to send (RTS/CTS)
  • Its an additional step in the CSMA process
  • when the channel is idle it sends a ‘request to send’ to the server
  • If its clear the server responds with a ‘clear to send’ message

A-level Computer Science (11 decks)

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