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OCR Computer Science > 1.3.3 Networks > Flashcards

1.3.3 Networks Flashcards

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1
Q

What is a network?

A

Two or more computers connected together that can transmit data

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2
Q

What is a physical topology?

A

The physical layout of a network

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3
Q

What is a logical topology?

A

The way in which data flows around a network

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4
Q

What is a bus topology?

A

Network topology where all terminals are connected to a backbone cable

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5
Q

What is the advantage of a bus topology?

A

Cheaper to set up as no additional hardware

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6
Q

What are the two disadvantages of a bus topology?

A

If backbone cable fails, entire network disconnected
As traffic increases, performance decreases

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7
Q

What is a star topology?

A

Uses a central node to direct the flow of data

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8
Q

What can be used as a central node in a star topology?

A

A switch
A computer

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9
Q

What are used to identify devices on a star topology?

A

MAC addresses

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10
Q

What are the five advantages of a star topology?

A

Perfomance is consistent
If one cable fails, only that node is affected
Transmits data faster
Easy to add new nodes
No data collisons

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11
Q

What are the two disadvantages of a star topology?

A

Expensive
If central switch fails, network fails

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12
Q

What is a mesh topology?

A

Every node is connected to every other node

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13
Q

What are the three advantages of a mesh topology?

A

No cabling cost
As nodes increase, reliabiity and speed of network increases
Faster due to no central switch

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14
Q

What is the disadvantage of a mesh topology?

A

Difficult to maintain

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15
Q

What are protocols?

A

Set of rules defining how two devices communicate with each other

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16
Q

What is the Internet?

A

A network of networks
Allows computers across the world to communicate

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17
Q

What is the TCP/IP stack?

A

A stack of networking protocols that work together to pass packets during communication

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18
Q

Name the four layers of the TCP/IP stack.

A

Application
Transport
Network
Link

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19
Q

What happens at the application layer?

A

Specifies what protocol needs to be used for the application being sent

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20
Q

What happens at the transport layer?

A

End-to-end connection established between source and destination
Splits & labels data into packets
Requests retransmission of any lost packets

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21
Q

What happens at the network layer?

A

Adds source and destination IP addresses
Routers use IP addresses to forward packets

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22
Q

What happens at the link layer?

A

The connection between the network devices
Adds the MAC address identifying the NIC of source and destination computer

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23
Q

Describe the layers of the TCP/IP stack on the recipient computer.

A

Link: Removes MAC addresses
Network: Removes IP addresses
Transport: Removes port number and reassembles packets
Application: Present data in form it was sent

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24
Q

What is a LAN?

A

A network spread over a small geographical area typically located on a single site
Hardware usually owned and controlled by the organisation using it

25
Q

What is a WAN?

A

A network that covers a large geographical area
Infrastructure leased from telecommunication companies who own and manage it

26
Q

What is a Domain Name System?

A

Method of naming internet resources
Hierarchy where each smaller domain is seperated from larger by a full stop

27
Q

What is the purpose of a DNS server?

A

Translate domain names into IP addresses when accessing a website

28
Q

What is circuit switching?

A

A method of communication where a direct link is created between two devices and maintained for entire conversation

29
Q

What is the advantage of circuit switching?

A

Quicker reconstruction as data arrives in logical order

30
Q

What are the two disadvantages of circuit switching?

A

Devices must transfer and recieve data at the same rate
Electrical interference from switches can corrupt or lose data

31
Q

What is packet switching?

A

A method of communicating packets of data across a network

32
Q

What are the three advantages of packet switching?

A

Methods to ensure data arrives
Multiple routes if one breaks
Can transfer packets over very large networks

33
Q

What is the disadvantage of packet switching?

A

Time is spent deconstructing and reconstructing data packets

34
Q

How are data packets split?

A

Header
Payload
Trailer

35
Q

What is included in the header of a packet?

A

Sender & recipient IP addresses
Protocol being used
Order of packets
Time to live / hop limit

36
Q

What is included in the payload of a packet?

A

The raw data

37
Q

What is included in the trailer of a packet?

A

Checksum / cyclic redundancy check

38
Q

What is the hop limit of a data packet?

A

Set by the source of the packet
Decremented by one each router (hop)

39
Q

Why is a hop limit needed?

A

To prevent data packets from circulating indefinitely with a network

40
Q

What is the checksum of a packet?

A

Value computed from a data packet to check whether data is received error free or not

41
Q

What is a firewall?

A

Device designed to prevent unauthorised access to a network

42
Q

Describe how a firewall works.

A

Two NICs between user and internet connection
Pass packets between two NICS and compares them against packet filters
Perform packet filtering

43
Q

What are packet filters?

A

A set of rules set by the firewall software

44
Q

What are proxy servers?

A

Intermediate that collects and sends data on behalf of user

45
Q

Give 3 features of proxy servers.

A

Protect privacy of usr who remains anonymous
Cache frequently used website data so faster to load
Reduce web traffic

46
Q

Give a use of proxy servers.

A

By administrators to prevent access to sensitive or irrevelant information at work/school

47
Q

What is a Network Interface Cards?

A

Required to connect a network
Assign a MAC address to each device

48
Q

What is a switch?

A

Used to direct the flow of data across network
Used in star topology

49
Q

What is a Wireless Access Point?

A

Allows devices to connect to a network wirelessly
More commonly used to connect devices to a router
Used in mesh networks

50
Q

What is a router?

A

Used to connect two or more networks
Includes ISPs network to allow Internet connection

51
Q

What is a gateway?

A

Translates protocols so that both networks have same protocols
Removes the header from packets before the remaining data is added with the new protocol of the new network

52
Q

What is a client-server network?

A

Terminals conncted to a server

53
Q

What is a client?

A

A terminal

54
Q

What is a server?

A

Powerful central computer
Holds all important information and has extra processing power the clients can request to use

55
Q

What are the three advantages of a client-server network?

A

More secure
Central backups
Sharing data and resources

56
Q

What are the three disadvantages of a client-server network?

A

Expensive set up
Trained staff are required to maintain server
Single point of failure

57
Q

What is a peer-to-peer network?

A

Computers are all connected

58
Q

What are the three advantages of a peer-to-peer network?

A

Inexpensive set up
Allows users to share resources
Easy maintenance

59
Q

What are the two disadvantages of a peer-to-peer network?

A

Less secure
No central backup

OCR Computer Science (29 decks)

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