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GCSE Computer Science > Section Two: Networks > Flashcards

Section Two: Networks Flashcards

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1
Q

Factors that affect network performance

A

Bandwidth
Wired connections/wireless connections
Choice of hardware
Network topology

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2
Q

Bandwidth

A

The amount of data that can be transferred in a given time. The greater the bandwidth, the better the network can perform. Available bandwidth is shared between users of a network - too many users or heavy use may cause congestion and slow the network. You can limit the bandwidth available to individual users to address this

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3
Q

Wired connections

A

Wired connections are generally faster and more reliable than wireless.
Fibre optic cables can give much better performance than copper cables.

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4
Q

Wireless connections

A

Wireless performance depends on signal quality so is affected by the range of the device, the amount of interference from other devices and physical obstructions like thick walls in buildings.

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5
Q

WAN

A
  • Wide Area Network
  • A WAN connects LANs that are in different geographical locations.
  • Unlike a LAN, organisations hire infrastructure from telecommunications companies, who own and manage the WAN because WANs are more expensive than LANs.
  • WANs may be connected using fibre or copper telephone lines, satellite links or radio links
  • The internet is one big WAN.
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6
Q

LAN

A
  • Local Area Network
  • Covers a small geographical area located on a single site.
  • All hardware is owned by the organisation that uses it.
  • Either wired or wireless
  • Used in businesses, schools and universities
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7
Q

Why use a LAN

A
  • Sharing files is easier - users can access the same files, work collaboratively and copy files between machines
  • Share the same hardware (printers) on a LAN
  • Internet connection can be shared between devices connected to a LAN
  • You can install and update software on all computers at once, rather than one-by-one
  • Communication with LAN users is cheap and easy (e.g with instant messaging)
  • User accounts can be stored centrally, so users can log in from any device in LAN
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8
Q

NIC

A

Network Interface Controller
An internal piece of hardware that allows a device to connect to a network. These can be used on separate cards, but nowadays they’re built into the motherboard. NICs exist for both wired and wireless connections.

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9
Q

Switches

A

Switches connect devices on a LAN. Switches receive data from one device and transmit this data to the device on the network with the correct MAC address.

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10
Q

Routers

A

Routers are responsible for transmitting data between networks - they’re always connected to at least two different networks. They have a crucial role on the Internet, directing data to their destination.

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11
Q

Ethernet Cables

A

Used to connect devices in a LAN. The most common ethernet cables are CAT 5e and CAT 6. They are ‘twisted pair’ cables, containing four pairs of copper wires which are twisted together to reduce internal interference.

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12
Q

Coaxial cables

A

Made of a single copper wire surrounded by a plastic layer for insulation and a metallic mesh which provides shielding from outside interference.

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13
Q

Fibre Optic Cables

A

Fibre Optic cables transmit data as light. They are high performance (and therefore expensive) cables - they don’t suffer interference and can transmit over very large distances without loss of signal quality.

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14
Q

How do you transmit data wirelessly?

A

Wireless networks use radio waves to transmit data.
To set up a wireless network, you need a Wireless Access Point (WAP) device.
To connect, devices need wireless capability. Many modern devices have the necessary hardware built in, but devices that don’t can often still connect to a wireless network using a dongle.

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15
Q

Wi-Fi

A

Wi-Fi uses two radio frequency bands - 2.4 GHz and 5 GHz
The bands are split into numbered channels that each cover a small frequency range. The channels in the 2.4 GHz band overlap

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16
Q

Factors that affect Wi-Fi performance

A
  1. Interference between networks using adjacent channels.
    - To avoid problems, only certain channels that are spaced apart tend to be used.
  2. The frequency band a network uses
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17
Q

Advantages of 2.4 GHz

A
  • Has a greater range, so can serve devices across a wider area
  • Better at getting through solid objects/walls
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18
Q

Advantages of 5 GHz

A
  • Much faster when communicating over a short distance

- There are more non-overlapping channels, so there’s less chance of interference from other devices

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19
Q

Client-server networks

A

A client-server network is managed by a server. The devices connected to the server are clients.
Files and software are usually stored centrally on the server rather than on individual client devices

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20
Q

Client-server relationship

A

Clients send requests to the server, e.g. asking for data

The server processes the request and responds

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21
Q

What do servers store?

A

Servers store user profile, passwords and access information - it may request a password before fulfilling certain requests or deny requests to users without the right access level

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22
Q

Pros of client-server (5)

A
  • Easier to keep track of files as they are stored centrally
  • Easier to perform backups
  • Easier to install and update software
  • Easier to manage network security
  • Servers are very reliable and are always on
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23
Q

Cons of client-server (3)

A
  • Expensive to set up and needs IT specialists to maintain the network and server
  • Server dependence - if the server goes down all clients lose access to their work
  • The server may become overloaded if too many clients are accessing it at once
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24
Q

Peer-to-Peer Network

A
  • In Peer-to-Peer networks all devices are equal, connecting directly to each other without a server.
  • You store files on individual devices and then share them with others
  • You may use a P2P network at home to share files between devices, or connect devices to a printer
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25
Q

Pros of P2P (2)

A
  • Easy to maintain - you don’t need any expertise or expensive hardware
  • No dependence on server - if one device fails the whole network isn’t lost
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26
Q

Cons of P2P (4)

A
  • No centralised management - devices need their updates and security installed individually. Backups are also more complicated.
  • Copying files between devices creates duplicate files; it’s easy to lose track of what’s stored where and which files are up-to-date.
  • Peer machines are less reliable and data may be lost if one fails
  • Machines are prone to slow down when other devices access them.
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27
Q

Star topology

A

All the devices are connected to a central switch or server that controls the network.
The central switch allows many devices to access the server simultaneously.
Star networks may be wired or wireless

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28
Q

Pros of star topology (3)

A
  • If a device fails or a cable is disconnected, the rest of the network is unaffected
  • It’s simple to add more devices to the network
  • Better performance than other setups - data goes straight to the central device so all devices can transmit data at once and there are few data collisions.
29
Q

Cons of star topology (2)

A
  • In wired networks, every device needs a cable to connect to the central switch or server. This can be expensive
  • If there is a problem with the switch/server, the whole network is affected
30
Q

Bus topology

A

In a bus topology, all devices are arranged in a line, connected to a single backbone cable. Devices send data in both directions. This causes data collisions, which slows the network

31
Q

Ring Topology

A

In a ring topology, data moves in one direction around the ring, preventing collisions. But only one device can send data at a time and data passes through many devices before reaching its destination

32
Q

Mesh topology

A

A mesh topology is decentralised - networking devices are either directly or indirectly connected to every other one without the need for one central switch or server. Mesh networks work by sending data along the fastest route from one device to another

33
Q

Main advantage of mesh topology

A

There is no single point where the network can fail. If one device fails then the data is sent along a different route to get to its target

34
Q

Main disadvantage of mesh topology

A

They are expensive if connecting the devices together using wires.
However more people now use wireless technology, making mesh networks a more practical option

35
Q

Protocol

A

A set of rules for how devices communicate and how data is transmitted across a network

36
Q

MAC addresses

A

Are assigned to all network-enabled devices by the manufacturer. They are unique to the device and can not be changed.

37
Q

IP address

A

Used when sending data between TCP/IP networks over the Internet.
They are not linked to hardware.
Assigned manually or automatically

38
Q

Static IP address

A

Permanent address
Used to connect printers on a LAN, and for hosting websites on the Internet
Companies don’t want the IP address of their website changing
They are expensive

39
Q

Dynamic IP address

A

Assigned when a device logs on to a network, meaning that it may have a different address every time it connects
ISPs often use dynamic IP addresses as they are more cost effective and can be reused

40
Q

Data Packet Header

A

Contains the control information.

Includes destination address and the source address and the packet number.

41
Q

Data Packet Payload

A

The reason why a data packet was sent in the first place.

Might be part of an email, document, web page or streamed video

42
Q

Checksum number

A

A form of validation used to check that the payload data hasn’t been corrupted during transit.

43
Q

Packet Switching

A

Used by routers to direct data packets on the Internet and other IP networks.

44
Q

TCP/IP

A

Protocol which dictates how data is sent between networks

45
Q

TCP

A

Transmission Control Protocol
Sets the rules for how devices connect on the network. Its in charge of splitting data into packets and reassembling the packets back to the original data .
Also responsible for checking data is correctly sent and delivered

46
Q

IP

A

Responsible for packet switching

47
Q

HTTP

A

Used by web browsers to access websites and communicate with web servers

48
Q

HTTPS

A

More secure than HTTP

Encrypts all information sent and received

49
Q

FTP

A

Used to access, edit and move files between devices on a network
E.g. to access files on a client computer

50
Q

POP3

A

Post Office Protocol
Used to retrieve emails from a server. The server holds the email until you download it, at which point it is deleted from the server.

51
Q

IMAP

A

Internet Message Access Protocol
Used to retrieve emails from a server. The server holds the email until you delete it - you only download a copy
Used by most web-based email clients

52
Q

SMTP

A

Used to send emails. Also used to transfer emails between servers

53
Q

Layer 1

A

Data Link layer
Passing data over a physical network. Responsible for how bits are sent as electrical signals over cables, wireless and other hardware
ETHERNET

54
Q

Layer 2

A

Network Layer
Making connections between networks, directing data packets and handling traffic. Used by routers
IP

55
Q

Layer 3

A

Transport Layer
Controlling data flow - e.g. splitting data into packets and checking packets are correctly sent and delivered
TCP

56
Q

Layer 4

A

Application Layer
Turning data into websites and other applications and vice versa
HTTP, FTP, SMTP

57
Q

Advantages of using layers

A
  • Breaks network communication into manageable pieces. Helps developers concentrate on one area
  • They can be changed without others being affected (because they’re self contained)
  • Having set rules for each layer forces companies to make compatible, universal hardware and software, so different brands will work with each other and always work in basically the same way
58
Q

WWW

A

A collection of websites that are hosted on web servers and accessed through the http protocol

59
Q

URL

A

an address that is used to access webs servers and resources on them

60
Q

DNS

A

Domain Name Server
Translates a website’s domain name into its IP address
The Internet has a set of DNS, meaning you don’t have to remember IP addresses to access websites

61
Q

Hosting

A

When a business uses its servers to store files of another organisation

62
Q

What is cloud computing or the ‘cloud’?

A

The use of internet hosting for general storage of user files which also provides online software. It acts like an extension of a traditional client-server network where user files are stored centrally on a network server.

63
Q

Pros of the cloud

A
  • Users can access files from any connected device
  • Easy to increase how much storage is available
  • No need to buy expensive hardware to store data
  • No need to pay IT staff to manage the hardware
  • Cloud host provides security and backups for you
  • Cloud software will be updated automatically
64
Q

Cons of the cloud

A
  • Need access to the Internet to access files
  • Dependent on host for security and backups
  • Data in the cloud can be vulnerable to hackers
  • Unclear who has ownership over cloud data
  • Subscription fees for using cloud storage and software may be expensive.
65
Q

What is a virtual network?

A

A network that is entirely software-based. Virtual networks are created by partitioning off some of a physical network’s bandwidth to form a separate network.

66
Q

Why are virtual networks more efficient than physical networks?

A

Several virtual networks can exist on the same physical network. These networks all share the same hardware, making virtual networks more efficient than standard physical networks.

67
Q

Why do virtual networks have better security?

A

Each virtual network has its own security, as well as its own firewall. This means virtual networks can only be accessed by using certain software or login information - other people could be using the same physical network and not have access to the virtual network or know that it exists.

68
Q

What is a VPN?

A

Virtual Private Network
A type of virtual network that can be used to send data securely over a large network, like a WAN or the Internet.
For example a VPN can be to send data securely between two offices on different sites, or to set up a school intranet that all students can access from home.

69
Q

What does a virtual LAN do?

A

A virtual LAN allows you to split a LAN into several separate networks using the same hardware.

GCSE Computer Science (8 decks)

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