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Networks Flashcards

1
Q

What is a computer network?

A

Two or more computers connected together to communicate to exchange information and data.

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2
Q

What are the advantages of computer networks?

A
  • share software stored in the main system
  • files can be easily shared between users
  • can communicate via email, instant messenger and VoIP (voice over IP)
  • more straightforward to back up data
  • data can be transmitted to remote areas that are connected to local areas
  • allow sharing common peripherals (e.g. printers) = save money
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3
Q

What are the disadvantages of computer networks?

A
  • cost of purchasing cable to construct a network as well as file servers = costly
  • management is complicated - needs training and a specialist network manager
  • files in server become inaccseible if server breaks down
  • if a virus gets into the system = spreads easily through a network
  • vunerable to hacking esp with WANs = need firewall
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4
Q

What are the 3 main types of networks?

A
  • Wide Area Networks - WANs
  • Local Area Networks - LANs
  • Personal Area Networks - PANs
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5
Q

Describe LANs

A
  • high speed transmission over a restricted geographical area
  • can be wired or wireless = schools/ unis
  • if it’s too large, the signal can be boosted
  • usually owned by a single person/ organisation
  • e.g. connect LANs to PCs, tablets, printers at homes
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6
Q

Describe WANs

A
  • WANs are used to link LANs that are separated by large distances (few m to thousands of km)
  • e.g. internet
  • often collective or distributive ownership as more expensive to set up than LAN
  • connected using telephone lines, satellite or radio links and organisations hire infrastructure to manage the WAN
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7
Q

Describe PANs

A
  • computer network organised around an individual so very short range
  • mobile computers, phones or PDAs
  • uses Bluetooth
  • handy as no additional hardware = can create a PAN on the move
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8
Q

What piece of hardware in a device allows it to connect to networks?

A
  • NICs = Network Interface card (used for wired and wireless connections)
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9
Q

What do switches do?

A
  • connect devices on a LAN
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10
Q

What do routers do?

A
  • transmit data between diff networks and are normally used to connect to the network
  • most routers in homes =a router, switch and WAP - all in one
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11
Q

How can wired networks be connected?

A
  • using diff cables

- choice of cable depends on cost, bandwidth and how far you want to transmit data

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12
Q

What is bandwidth?

A
  • amount of data that can be sent across a network at a given time
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13
Q

What are the 3 diff cables for connecting networks?

A
  • Fibre optic cables
  • CAT 5c and CAT 6
  • Coaxial cables
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14
Q

In what circumstances are fibre optic cables used?

A
  • can transmit data as light = high performance
  • expensive
  • don’t suffer inference
  • can transmit over large distances at a high bandwidth without loss of quality
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15
Q

In what circumstances are CAT 5c and CAT 6 used?

A
  • common Ethernet cables
  • contain pairs of copper wires which are twister to reduce internal interference
  • cheaper than fibre optic
  • decent bandwidth
  • thus commonly used in houses for LANs networks
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16
Q

In what circumstances are coaxial cables used?

A
  • made of a single copper wire surrounded by plastic layer for insulation and metallic mesh for shielding from outside interference
  • very cheap
  • low bandwidth
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17
Q

What are the 2 categories of networks?

A
  • wired

- wireless

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18
Q

What is the generic term for things such as wifi?

A
  • WLANs

- Wireless Local Area Networks

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19
Q

What do wireless networks use to transmit data?

A
  • radio waves
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20
Q

What is needed to set up a wireless network?

A
  • wireless access point (WAP) device
  • switch that allows devices to connect wirelessly
  • WAP is not hotspots which are locations where you can connect to a WAP
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21
Q

How can devices without wireless capability connect?

A
  • use a dongle
  • USB dongle = can be plugged into computers to allow them to connect wirelessly to the internet
  • HDMI dongles = use wireless networks to streak high-quality video to a TV
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22
Q

What are the benefits of wireless networks ?

A
  • convenient as you can get it to connect automatically to the network and you can also move around while connected
  • cheaper and better for the environment (don’t need wires)
  • easy to add more users to a wireless network - don’t need to install extra wires or any complex setup
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23
Q

What are the drawbacks of wireless networks?

A
  • generally less secure than wired networks and access points are visible to all devices, not just trusted ones = allows hackers to gain access
  • distance from WAP, interference from other wireless networks, physical obstructions can reduce signal strength - limit on how far they can reach
  • lower bandwidth and less reliable
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24
Q

Describe a star topology?

A
  • all devices are connected to a central switch or server that controls the network
  • central switch allows many devices to access the server simultaneously
  • star networks may be wired or wireless
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25
Q

What are the pros of star topologies?

A
  • if a device fails or a cable is disconnected, the rest of the network in unaffected
  • simple to add more devices since each device is connected using a separate cable
  • better performance than other setups and data goes straight to the central device so all devices can transmit data at the same time
  • fewer data collisions compared to other network topologies
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26
Q

What are the cons of a star topology?

A
  • wired networks = every device needs their own cable = expensive
  • switch itself is also an expensive piece of hardware
  • problem with the switch or server = whole network is affected
  • maximum numbers of possible connections is determines by the switch = if you need more, need to buy a new one
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27
Q

What is bus topology like?

A
  • connected to a single cable
  • use a single ‘backbone’ cable, called a bus to connect all the devices
  • 2 terminators are placed at the ends of the bus to stop data reflecting back along the bus
  • without terminators, reflected signals would cause interference and potentially make network unstable
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28
Q

What are the pros of a bus topology?

A
  • like star, the network is unaffected if a device fails
  • aren’t dependent on central switch
  • relatively cheap to set up compared to star network as total length of wiring is cheaper than switches, both to buy and maintain
29
Q

What are the cons of bus topologies?

A
  • data collisions are common on a bus network =data must be resent if collision = slows network down
  • more devices you add to network = more likely collisions = unsuitable for larger networks
  • to avoid collisions = devices must wait for the bus to be available before they can send any data = can also slow the network down
  • if bus cable broken = splits network into separate parts without terminators at both ends = lots of reflected network = shuts down entire network
30
Q

Define a network protocol

A
  • a protocol is a set of rules for how devices communicate and how data is transmitted across the network
  • covers how communication between 2 devices should start and end, how data should be organised and what to do if the data goes missing
  • data is split into equally sized packets and each packet has extra information like the destination and source address and a checksum (used to find errors)
31
Q

What is a layer?

A
  • network protocols are divided into layers
  • layer is a group of protocols which have similar functions
  • layers are self contained - protocols in each layer do their job without needing to know what’s happening in the other layers
  • each layer serves the layer above it
  • data can only be passed between adjacent layers
32
Q

How many layers are there in the TCP/IP model?

A

4 layers

  • application
  • transport
  • internet
  • link
33
Q

Describe layer 1?

A

Layer 1 - Link layer

  • passing data over the physical network
  • responsible for how data is sent as electrical signals over cables, wireless and other hardware and interpreting signals using a device driver
34
Q

What is an example of a protocol in the link layer?

A

WiFi or Ethernet

35
Q

Describe layer 2?

A
  • Layer 2 = internet layer
  • adding IP addresses to data packets, directing them between devices and handling traffic
  • used by routers
36
Q

What is an example of a protocol in the internet layer?

A

IP

37
Q

Describe layer 3?

A
  • Layer 3 = Transport Layer
  • setting up communications between 2 devices
  • splitting data into packets and checking packets are correctly sent and delivered
38
Q

What is an example of a protocol in the transport layer?

A
  • TCP, UDP
39
Q

Describe layer 4?

A

Layer 4 = application layer

  • proving networking services to applications
  • Turing data into websites
40
Q

What is an example of a application in the link layer?

A
  • HTTP
  • FTP
  • SMTP
41
Q

What is the advantage of using layers?

A
  • breaks network communication into manageable pieces - helps developers concentrate on only one area of the network
  • layer area self - contained = they can be changed without the other layers being affected
  • set rules for each layer forced companies to make compatible, universal hardware and software so different brands will work with each other and always work in the same way
42
Q

What is the application responsible in the TCP/IP model?

A
  • file, email and data transfer
43
Q

What are the protocols in the application layer?

A
  • HTTP - hyper text transfer protocol
  • HTTPS - http secure
  • FTP - file transfer protocol
  • IMAP - internet message access protocol
  • SMTP - simple mail transfer protocol
44
Q

What is HTTP and HTTPS used for?

A

HTTP is used by web browsers to access websites and communicate with web servers

HTTPS is a more secure version of HTTP and encrypts all information sent and received

45
Q

What is FTP used for?

A
  • used to access, edit and move files between devices on a network
  • e.g. to access files on a server from a client computer
46
Q

What is IMAP used for?

A
  • used to retrieve emails from a server
47
Q

What is SMTP used for?

A
  • used to send emails

- also used to transfer emails between servers

48
Q

What are TCP and UDP?

A
  • transport layer protocols which control the packaging and unpackaging of data
  • splits the data into packets
49
Q

Describe TCP

A
  • transmission layer protocol establishes a connection between sending and receiving devices
  • splits data into numbered packets that can be reassembled into the original data once they reach destination, even if they arrive out of order
  • communicates with the receiving device to make sure all packets have been transferred correctly - if not then missing or corrupted packets are resent
  • sending device gets confirmation when the transfer is complete
50
Q

Describe UDP

A
  • user data gram protocol breaks data down into packets without numbering them
  • read by the receiving device in the order they arrive - even if it’s not in they were sent
  • UDP sends one packet at once and doesn’t check with the receiving device that everything has been received
  • this saves time but there’s no way of knowing if packets have gone missing in transit
51
Q

When is UDP more suitable?

A
  • suitable for applications that need fast, efficient transmission (e.g. live video streaming)
  • hiccup in video quality from missing packet is better than a delay in the life stream
52
Q

When is TCP more suitable?

A
  • better when you need a reliable connection (e.g. downloading files)
  • missing data packets can cause files to be corrupted and unusable but you wouldn’t want to have to redownload the whole file
53
Q

What is an IP responsible for?

A
  • packet switching

- internet protocol = IP

54
Q

What layer does IP operate on?

A
  • Internet layers
  • establishes connections between routers and handles network traffic - IP addresses are unique numbers assigned to every device connected to an IP network - added to the header of each packet at the internet layer
55
Q

What is the IP responsible for?

A
  • directing data packets to their destination across the internet or other IP networks using packet switching
  • each packets is sent between a series of routers within reads each ones header and decides which router to send the packet to next
  • way the data sent changes depending on network traffic - packets can take diff routes and routers may prioritise packets
56
Q

Why is packet switching efficient?

A
  • so many possible routes that each packet can take

- so packets receive device quickly even if there’s heavy traffic

57
Q

What is WIFI the standard protocol for?

A
  • wireless LANS
58
Q

At which layer does WiFi operate?

A
  • link layer
  • units of data sent in the link layer are called frames, not packets
  • uses MAC address for frames to devices
59
Q

What bands does WiFi use and when is each band better?

A
  • uses 2 radio Hz bands
  • 2.4 GHz and 5GHz
  • 2.4 GHz has a greater range and is better at getting through walls and other obstructions while 5GHz is better over short distances
60
Q

What are the Hz bands split into?

A
  • split into numbered channels that each cover a small Hz range
  • some channels in the 2.4 GHz band overlap
  • networks using adjacent or overlapping channels can cause interference
61
Q

What security protocols encrypt data in WiFi?

A
  • WPA (WiFi protected access)

- WPA2

62
Q

What is Ethernet?

A
  • family of protocols that operates on the link layer

- handles the transmission of data between 2 devices on LANs but Ethernet is specifically used for wired connections

63
Q

What is a node?

A

A device in a network topology

64
Q

How can networks be protected against threats?

A
  • encryption
  • anti-malware software
  • user access levels
  • automatic software updates
  • MAC address filtering
65
Q

How can networks be protected with encryption?

A
  • when data is translated into a code when only someone with the correct key can access
  • cipher text into plain text
  • needed to send data over network securely
66
Q

How can networks be protected with anti-malware software?

A
  • stops malware from damaging the network
  • e.g. firewall examines all data and blocks potential threats
  • prevents unauthorised access into the network
67
Q

How can networks be protected with user access levels?

A
  • some have higher access levels than others and access to more sensitive data
  • limits the number of people with access to important data so prevents attacks within an organisation
68
Q

How can networks be protected with automatic software updates?

A
  • used to fix security holes

- unpatched software can be easily exploited

69
Q

How can networks be protected with MAC address filtering?

A
  • way of making sure only people on a network are trusted users
  • checks unique identification so only allowed devices can join the network

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