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OCR COMPSCI OFFICIAL > 1.3.3 - Networks > Flashcards

1.3.3 - Networks Flashcards

1
Q

What is a network?

A

A network is the name given to two or more computers connected together with the ability to transmit data between each other

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2
Q

What is a LAN?

A

A network which is spread over a small geographical area or a single site

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3
Q

What is a WAN?

A

A wide area network (or WAN) is the name given to a network which is spread over a large geographical area.
Normally requires equipment rented from telecommunications companies.
Made of lots of LANS connected to one another

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4
Q

What is a physical topology?

A

The physical layout of the wires and components which form the
network.

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5
Q

What is a logical topology?

A

The layout which shows how data flows.

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6
Q

What is a bus topology?

A

In a bus topology, all the terminals (devices) are connected to a backbone cable, the ends of which are plugged into a terminator.

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7
Q

What are the advantages of a bus topology?

A

Relatively inexpensive to set up
Doesn’t require any additional hardware

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8
Q

What are the disadvantages of a bus topology?

A

If backbone cable fails, the entire network gets disconnected
As traffic increases, performance decreases
All computers can see the data transmission

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9
Q

What does a star topology use to direct and identify devices in the network?

A

Star topologies use a central node, often a switch, to direct data through the network.
MAC (Media Access Control) addresses, which are unique to a device, are used to identify each device on the network.

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10
Q

What are the advantages of a star topology?

A

-Performance is consistent even with heavy network traffic
- If one cable fails, only that single terminal is affected
- Transmits data faster, giving better performance than bus topology
- Easy to add new stations.
- No data collisions

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11
Q

What are the disadvantages of a star topology?

A

Expensive due to switch and cabling
If the central switch fails, the rest of the network fails

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12
Q

What is a mesh topology?

A

In a mesh topology, every node is connected to every other node. Mesh
topologies are most commonly found with wireless technology such as
Wi-Fi.

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13
Q

What are the advantages of a mesh topology?

A

● If using a wireless network, there is
no cabling cost
● As the number of nodes increase,
the reliability and speed of network
becomes better
● Nodes are automatically
incorporated
● Nodes don’t go through a central switch, improving speed.

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14
Q

What are the disadvantages of a mesh topology?

A

● If using a wireless network, devices
with wireless capability (which increases cost) must be purchased.
● If using a wired network, a large quantity of cable is required compared to other network topologies like bus and star. This is
expensive.
● Maintaining the network is difficult

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15
Q

What is a protocol?

A

A protocol is a set of rules defining how two computers communicate with each other.

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16
Q

Where are protocols found?

A

Protocols are standard so that all devices have a designated method of communicating with each other, regardless of manufacturer.

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17
Q

What are HTTP and HTTPS used for?

A

HyperText Transfer Protocol/Secure
Web page rendering (HTTPS is an encrypted version)

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18
Q

What is TCP/IP used for?

A

Transmission Control Protocol/Internet Protocol
Networking protocol used in the routing of packets through networks.

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19
Q

What is POP3 and IMAP used for?

A

Post Office Protocol and Internet Message Access Protocol.
Mailing protocols used for email access.

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20
Q

What is FTP?

A

File transfer protocol, used for the transmission of files over networks.

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21
Q

What is the Internet?

A

The Internet is a network of networks which allows computers on opposite sides of the globe to communicate with each other. Continents are connected to each other using large international backbone cables. Many of these pass underwater, linking continents to one
another.

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22
Q

What is the application layer?

A

The application layer is based at the top of the stack. It specifies what
protocol needs to be used in order to relate the application that’s being sent.

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23
Q

What is the transport layer?

A

The transport layer splits data up into packets and labels these packets with their packet number, the total number of packets the original data was split
up into and the port number being used for communication.
If any packets get lost, the transport layer requests retransmissions of these
lost packets.

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24
Q

What protocol does the transport layer use?

A

The transport layer uses TCP to establish an end-to-end connection
between the source and recipient computer.

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25
Q

What is the network layer?

A

The network layer adds the source and destination IP addresses. (The
combination of the IP address and the port number is called a socket
address.)
The sockets are then used to specify which device the packets must be sent
to and the application being used on that device.

26
Q

What operates on the network layer?

A

Routers operate on the network layer and the router is what uses the IP
addresses to forward the packets.

27
Q

What is the link layer?

A

The link layer is the connection between the network devices, it creates a physical connection between the network nodes and adds the
MAC address identifying the Network Interface Cards of the source and
destination computers.

28
Q

What is the destination MAC address?

A

For devices on the same network, the destination MAC address is the
address of the recipient computer, otherwise, it will be the MAC address of
the router.

29
Q

Why can the TCP/IP protocol be described as a stack?

A

The layers are looked at from bottom to top, ending with the application layer presenting the data to the recipient in the requested form.

30
Q

What is the DNS system?

A

The system used to name and organise internet
resources. It is a hierarchy, in which each smaller domain is separated from the larger
domain by a full stop.
It translates DNS to IP addresses.

31
Q

Why are domain names used?

A

They are much easier to remember than IP addresses.

32
Q

What is a packet?

A

A segment of data

33
Q

What does a packet header contain?

A

Sender and recipient IP addresses.
Protocol being used
Order of the pacets
Time to Live

34
Q

What is TTL/Hop Limit?

A

The Time To Live (TTL), tells the packet when to expire so that it does
not travel forever.

35
Q

What does a packet payload contain?

A

Raw data to be transmitted

36
Q

What does a packet trailer contain?

A

Checksum, or cyclic redundancy check - a code used to detect whether any errors have occurred during transmission.

37
Q

What is packet switching?

A

Packet switching is a method of communication in which data is communicated using packets across a network.
In this method of communication, packets are sent across the most efficient route, which can vary for each packet.

38
Q

What are the advantages of packet switching?

A
  • Multiple methods to ensure data arrives intact
  • Multiple routes, so if one path breaks another can be used.
  • Packets can be transferred across very large networks for global communication.
39
Q

What are the disadvantages of packet switching?

A
  • Time is spent deconstructing and reconstructing the data packets.
  • Must wait for all packets to arrive before data can be received.
40
Q

What is circuit switching?

A

Circuit switching is a method of communication where a direct link is created between two
devices.
This direct link is maintained for the duration of the entire conversation between
devices.
Circuit switching requires the two devices to transfer and receive data at the
same rate.

41
Q

What are the advantages of circuit switching?

A
  • Data arrives in a logical order which results in a quicker reconstruction of the
    data.
  • Enables two users to hold a call without delay in speech
42
Q

What are the disadvantages of circuit switching?

A
  • Bandwidth wasted when no data is being sent,
  • Devices must transfer and receive data at the sane rate,
  • Using switches produces electrical interference, which can corrupt or destroy data.
  • Means sections of the network can’t be used by others while transmission is being completed.
43
Q

What is a firewall?

A

A firewall is a device designed to prevent unauthorised access to a network.
A firewall consists of two network interface cards (NICs) between the user and the Internet

44
Q

How does a firewall work?

A

The firewall passes packets between two NICs and compares them against a set of rules set by the firewall software. The preconfigured rules are called packet filters.

45
Q

What does packet/static filtering do?

A

It limits network access in accordance with administrator rules
and policies. It works by examining the source IP, destination IP and the protocols being
used as well as the ports being requested.

46
Q

What happens when access is denied by a firewall?

A

The packet can either be
dropped or rejected. A rejected packet sends an alert to the sender to notify them of the error whereas a dropped packet will not.

47
Q

What does a proxy server do?

A

A proxy server acts as an intermediary, collecting and sending data on behalf of the user

48
Q

What are the benefits of using proxies?

A
  • User remains anonymous, so privacy protected.
  • Can cache frequently used website data, making easier to load.
  • Reduces overall web traffic.
  • Used by admin to prevent access to sensitive/irrelevant content.
49
Q

What is an NIC?

A

A network interface card is the card required to connect a device to a network. This is usually built into the device and
assigns a unique media access control (MAC) address to each device

50
Q

What is a MAC address?

A

A 48-bit value coded into
the NIC, usually written as a twelve digit
hexadecimal number

51
Q

What is a switch?

A

A switch is a device used to direct the flow of data across a network

52
Q

What is a Wireless Access Point?

A

This is a device which allows a device to connect to a network.
It is more commonly combined with a router to enable internet access.

53
Q

What is a router?

A

A router is used to connect two or more networks together. Routers allow private, home
networks to connect to the Internet.

54
Q

What is a gateway?

A

A gateway is used when protocols are not the same between networks.
It translates the
protocols so that networks can communicate with each other.
Gateways work by removing the header from packets before adding the data to packets using the new protocol.

55
Q

What is a client-server network?

A

Client-server networks consist of terminals known as clients connected to a server.
The server is a powerful, central computer. The server holds all of the important information
and resources and has greater processing power than the terminals.
Clients can request
to use the server.

56
Q

What are the advantages of a client-server network?

A
  • More secure, as data is centrally stored.
  • Central backups
  • Shared data and resources
57
Q

What are the disadvantages of a client-server network?

A
  • Relatively expensive to set up.
  • If server fails, network performance fails.
  • Trained staff required for maintenance
58
Q

What is a peer to peer network?

A

A network in which computers are connected to each other so that they can share files.
Each device effectively acts as both a server and client, as it can both provide and request resources.

59
Q

Where are p2p networks used?

A

In piracy, because it is almost impossible to trace file origin.

60
Q

What are the advantages of P2P networks?

A

● Cheaper to set up
● Allows users to share resources
● Easy to maintain
● Not dependent on a central server
● Specialist staff are not required

61
Q

What are the disadvantages of P2P networks?

A

● Impossible to trace the origin of files
● Backups must be performed
separately
● Poorer security
● May be difficult to locate resources

OCR COMPSCI OFFICIAL (29 decks)

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