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OCR Computer Science A Level > 1.3.3 Networks > Flashcards

1.3.3 Networks Flashcards

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1
Q

Network

A

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

LAN (local Area Network)

A

-spread over a small geographical area or single site

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3
Q

WAN (wide area network)

A

-spread over a large geographical area

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4
Q

Bus Topology

A

All the terminals (devices) are connected to a backbone cable, the ends of which are plugged into a terminator

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5
Q

Bus Advantages

A
  • relatively inexpensive to set up

- doesn’t require any additional hardware

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6
Q

Bus Disadvantages

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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7
Q

Star Topology

A

Uses a central node, often a switch, to direct data through the network. Every device on the network is connected to the switch

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8
Q

Star Advantages

A
  • performance is consistent even with heavy network traffic
  • if one cable fails, only that station is affected
  • easy to add new stations
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9
Q

Star Disadvantages

A
  • expensive due to switch and cabling

- if the central switch fails the rest of the network fails

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10
Q

Mesh Topology

A

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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11
Q

Mesh advantages

A
  • if using a wireless network, there is no cabling cost
  • as the number of nodes increases, the reliability and speed of the network gets better
  • nodes are automatically incorporated
  • nodes don’t go through a central switch, improving speed
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12
Q

Mesh disadvantages

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 topologies like bus and star
  • maintaining the network is difficult
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13
Q

Protocol

A

is a set of rules defining how two computers communicate with each other.
Protocols are standard so that all devices have a designated method of communicating with each other, regardless of manufacturer

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14
Q

HTTP

A

Hyper Text Transfer Protocol - used for page rendering

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15
Q

POP3 and IMAP

A

used for the transmission of files over networks

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16
Q

TCP/IP

A

A stack of networking protocols that work together passing packets during communication.

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17
Q

Internet

A

A network of networks which allows computers on opposite sides of the globe to communicate with each other.

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18
Q

Application Layer

A
  • specifies the protocol that needs to be used. I.e. if application is a web browser then it would select the HTTPS protocol
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19
Q

Transport Layer

A
  • establishes an end-to-end connection between the source and the recipient computer
  • it splits data up into packets with their packet numbers
20
Q

Network Layer

A
  • Adds the source and destination IP addresses

- Routers use the IP addresses and sockets to forward the packets to the specified destination

21
Q

Link Layer

A

Adds the MAC address identifying the Network Interface Cards of the source and destination computers

22
Q

DNS (Domain Name System)

A

Used to name and organise internet resources. Domain names are much easier to remember than IP addresses, making it easier for users to quickly search for web pages

23
Q

Data Packets

A

Segments of data.

24
Q

Header

A
  • sender and recipients IP addresses
  • protocol being used
  • order of the packets
  • time to live ( tells packet when to expire so is not travelling forever)
25
Q

Payload

A

The raw data that is needed to be transmitted

26
Q

Trailer

A

Checksum

27
Q

Packet Switching

A

Method of communication in which data is split into equal sized packets and sent across a network using the most efficient route.

28
Q

Packet Switching Advantages

A
  • multiple methods to ensure data arrives intact i.e. checksum
  • multiple routes can be used
  • packets can be transferred over very large networks to allow communication globally
29
Q

Packet Switching Disadvantages

A
  • time is spent deconstructing and reconstructing the data packets
  • must wait for all packets to arrive before data can be received
30
Q

Circuit Switching

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. This requires the two devices to transfer and receive data at the same rate

31
Q

Circuit switching advantages

A
  • data arrives in logical order which results in a quicker reconstruction of the data.
  • enables two users to hold a call without delay in speech
32
Q

Circuit switching disadvantages

A
  • bandwidth is wasted during periods of time where no data is being sent
  • devices must transfer and receive data at the same rate
  • using switches means electrical interferences can be produced which can corrupt and destroy data
  • tied up sections of the network which cannot be used by others data until transmission has been completed
33
Q

Firewalls

A

A device designed to prevent unauthorised access to a network. A firewall consists of two NICs between the user and the internet. The firewall passes the packets between these two NICs and compares them against a set of rules set by the firewall software. (packet filters)

34
Q

Proxies

A

Acts as an intermediary, collecting and sending data on behalf of the user

35
Q

encryption

A

makes data unreadable using a set of keys if it is intercepted

36
Q

NIC

A

Network Interface Card is a card required to connect a device to a network. It assigns a unique MAC address to each device

37
Q

Switch

A

Device used to direct the flow of data across a network

38
Q

WAP (wireless access point)

A

Device that allows a device to connect to a network, commonly combined with a router to enable internet access.

39
Q

Routers

A

used to connect two or more networks together.

40
Q

Gateway

A

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

41
Q

Client server

A

clients connected to a server. The server is a powerful central computer.

42
Q

Client server advantages

A
  • more secure as data is stored in one location
  • central backups are carried out which are easier than individual backups
    data and resources can be shared between clients
43
Q

Client server disadvantages

A
  • relatively expensive to set up
  • functionality of terminals depends on the server; if this fails, performance fails
  • trained staff are required to maintain the server
44
Q

Peer to peer

A

computers are connected to each other so they can share files. Each device effectively acts as both a server and client.

45
Q

Peer to peer advantages

A
  • cheaper to set up
  • allows users to share resources
  • easy to maintain
  • not dependent on a central server
  • no specialist staff needed
46
Q

peer to peer disadvantages

A
  • impossible to trace the origin of files
  • backups must be performed individually
  • poorer security
  • may be difficult to locate resources

OCR Computer Science A Level (15 decks)

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