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Computer Science > Topic 4 - Networks > Flashcards

Topic 4 - Networks Flashcards

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1
Q

What is a network?

A

An arrangement of two or more computer devices connected together in order to communicate with each other and share resources.

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2
Q

7 reasons for connecting computers on a network:

A

1) Share data and software
2) Share printers, hard drives etc.
3) Share internet connection
4) Support and backup services
5) Enable the rapid deployment of new software and updates
6) Enable people to communicate with each other
7) Collaborative working

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3
Q

What does LAN stand for?

A

Local area network

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4
Q

Explain a bit out a LAN.

A
  • It’s a network in a small area such as a home, school, office building or a group of buildings on a single site
  • It exists in a small geographical area
  • Usually managed by a local manager or team on site
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5
Q

What does WAN stand for?

A

Wide area network

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6
Q

Explain a bit about WAN.

A
  • It connects separate LANs over a larger geographical area
  • Large companies can connect LANs at their different sites in order to share resources and data
  • Computers in a WAN can communicate with computers and users in other locations
  • The WAN will be managed by several different people or parts of an organisation working together
  • Or each LAN could be managed independently
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7
Q

What is the internet?

A

A global system of interconnected computer networks. It links together billions of digital devices worldwide. It is the world’s largest public WAN.

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8
Q

In what form does data travel across the internet?

A

In packets using a method called packet switching.

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9
Q

Describe the four stages of packet switching.

A

1) the senders large files is broken up into packets
2) packets are sent to their destination by routers
3) packets are sent down different most efficient routes
4) the receiving computer reassembles the muddled up packets in the correct order using info in the packet headers

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10
Q

What do routers do?

A

They form a physical connection between two or more networks and forward data packets from one network to another.

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11
Q

What does a routing table do when it receives a packet?

A
  • finds the packets destination address
  • uses its routing table to select the most efficient route for the packet to take on the next leg of its journey
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12
Q

What three things does a data packet consist of?

A
  • payload
  • header
  • footer
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13
Q

What five things does a header of a data packet tell you?

A

IP address of destination
IP address of source
Sequence number
Total number of packets
Checksum

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14
Q

What’s the payload of a data packet?

A

Part of the data for a web page, an email, a streamed movie, etc

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15
Q

What’s a footer for a data packet?

A

End of packet flag.

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16
Q

What four things does the receiving computer do?

A
  • Check that each packet is complete and uncorrupted
  • Check that all the data packets that where sent have been received
  • If necessary, ask the source computer to resend a corrupt or missing packet
  • Reassemble the packets in the correct order
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17
Q

What’s the modern type of cable?

A

Fibre-optic cable

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18
Q

How does a fibre-optic cable transfer data?

A

Pulses of light

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19
Q

Advantages of fibre optic cables?

A
  • Better bandwidth
  • Better range
  • Immune to electrical interference (latency)
  • Used long distance
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20
Q

Disadvantages of fibre optic cables

A

More expensive
More fragile
Difficult to handle

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21
Q

Define range

A

The distance over which data can be transferred

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22
Q

Define bandwidth

A

The volume of data that can be transferred measured in bits per second

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23
Q

Define latency

A

The time lag between data leaving its source and arriving at its destination measured in milliseconds. Electrical interference is one factor that affects latency.

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24
Q

How does wireless transmission media transmit data through the air?

A

Radio waves

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25
Q

Give some examples of wireless transmission media (5)

A

Wi-Fi
Bluetooth
Signed
RFID
NFC

26
Q

What two wireless transmission media have the longest range?

A

Wi-Fi- Up to 100m but physical objects can obstruct the signals
Zigbee- Up to 100m

27
Q

What wireless transmission media has the highest power consumption? And which is lowest?

A
  • Wi-Fi highest
  • NFC very low or none
28
Q

Uses of Wi-Fi

A

To network devices in LANs and to connect devices to the internet

29
Q

Uses of bluetooth

A

To pair devices over short distances, e.g. linking a headset to a phone

30
Q

Uses of a zigbee

A

Home aoutomation and internet of things, e.g. smart light bulbs

31
Q

Use of RFID

A

Security tags, passports and implants

32
Q

Use of NFC

A

Contactless payment systems

33
Q

Advantages of wireless LANs (2)

A
  • Easy instilation
  • Highly flexible
34
Q

Advantages of wired LANs (4)

A
  • Long range
  • High bandwidth
  • Low latency
  • Good security
35
Q

Disadvantages of wireless LANs (4)

A
  • Shorter range
  • Low bandwidth
  • High latency
  • Poor security
36
Q

Disadvantages of wired LANs (2)

A
  • Difficult instillation
  • Limited flexibility
37
Q

Units of measurement for data transfer rate

A

bits per second 1
bytesp.s. 8
kilobyte p.s. 1000
megabyte p.s. 1000^2
gigabyte p.s. 1000^3

38
Q

Units measurement for file size

A

bit 1
byte 8
kibibyte 1024 x 8
mebibyte 1024^2 x 8
gibibyte 1024^3 x 8
tebibyte 1024^4 x 8

39
Q

What’s the formula for the time it takes for a file to reach its destination

A

Time (in seconds) = File size (in bits) / Data transfer rate (in bps)

40
Q

Define protocol

A

The rules that govern how data must be formatted, transmitted and received on a network.

41
Q

What are the six application layer protocols?

A

FTP
HTTP
HTTPS
SMTP
POP
IMAP

42
Q

What is an FTP?

A

File type protocol. It provides the rules for file transfer between computers. It is often used to transfer files that are too large for attachment to emails.

43
Q

What is an HTTP?

A

Hyper-text transfer protocol. It provides the rules to be followed by a web browser and a web server when requesting and supplying information.

44
Q

What is HTTPS?

A

Hyper-text transfer protocol secure. Ensures the communications between a host and a client are secure by encrypting communications.

45
Q

What’s SMTP?

A

Simple mail transfer protocol. Provides the rules for sending email messages from client to server and then from server to server until it reaches its destination.

46
Q

What’s POP?

A

Post office protocol. Is used by a client to retrieve emails from a mail server.

47
Q

What’s IMAP?

A

Internet message access protocol. Unlike POP, the messages do not have to be downloaded. They can be read and stored on the message server.

48
Q

What is TCP/IP?

A

A hierarchical set (or stack) of network protocols, that work together to enable devices to communicate with each other over the internet.

49
Q

What’s the order of the four-layer protocol stack?

A

Sending computer –> application layer –> transport layer –> internet layer –> link layer

50
Q

What’s the purpose of the application layer?

A

Sending: provides the interfaces and protocols needed by the user.
Receiving: displays received information to the user.

51
Q

What protocols are used in the application layer?

A

FTP, HTTP, HTTPS, SMTP, POP, IMAP

52
Q

What is the purpose of the transport layer?

A

Sending: splits outgoing data into packets and numbers them. Adds a header containing a sequence number and a checksum to each packet.
Receiving: checks incoming packets and sends a resend request for any that have been damaged or lost in transit. Notifies the sender when all packets have arrived. Reassembles packets back into the correct order and passes the data up to the appropriate protocol in the application layer.

53
Q

What protocol is found in the transport layer?

A

TCP

54
Q

What’s the purpose of the internet layer?

A

Sending: adds the source and destination IP
Receiving: strips address info from incoming packet headers

55
Q

What protocol can be found in the internet layer?

A

IP

56
Q

What is the purpose of the link layer?

A

Sending: uses network-specific protocols to convert binary data into electrical, light or radio signals for network transmission
Receiving: converts incoming signals into binary data

57
Q

What protocols can be found in the internet layer?

A

IP

58
Q

What are the four network topologies?

A
  1. Bus
  2. Star
  3. Ring
  4. Mesh
59
Q

What are the three main importance’s of network security?

A
  • Business success
  • Privacy
  • Financial
60
Q

What is a firewall?

A

A hardware or software which protects a network connected to a WAN. They can be configured to prevent communications from entering the network and also programs and users from accessing the internet from within the network.

Computer Science (8 decks)

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