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computing > unit 5 - fundamentals of computer networks > Flashcards

unit 5 - fundamentals of computer networks Flashcards

1
Q

what is the internet?

A

the internet is a group of interconnected networks

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2
Q

what is the world wide web?

A
  • information system of interlinked webpages and other resources
  • accessed from web browsers; chrome, safari, edge
  • makes use of HTTP to send and receive data
  • the world wide web is one of the many services that make use of the internet
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3
Q

what is a WAN?

A

WIDE AREA NETWORK
- any network in which the computers communicate via resources of a third party network such as BT
- usually covers a wide geographic area - can connect networks at remote locations
uses cables, telephone lines, satellites or radiowaves to connect two or more remote locations

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4
Q

who uses a WAN?

A

organisations such as universites and school which have different locations; large, multi-national companies, goverments, research organisations

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5
Q

what is an example of a WAN?

A

the internet

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6
Q

what is a LAN?

A

LOCAL AREA NETWORK
- wires/cables and a main server
- smaller geographical area, usually just one site/location

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7
Q

who uses a LAN?

A

operates on a single site like a school or hotel who use their own cabling system

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8
Q

what is a PAN?

A

PERSONAL AREA NETWORK
- any network that connects computer devices near to a person
- usually carried out with bluetooth

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9
Q

what uses a PAN?

A

bluetooth speakers/headphones, connecting smart phones to cars

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10
Q

advantages of using networks

A
  • computers can share resources such as printers
  • files can be accessed through any computer in the network
  • data is easy to back up as it is stored centrally on the server
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11
Q

disadvantages of networks

A
  • purchasing the network hardware is expensive
  • managing a large network is complicated
  • viruses may be able to infiltrate the network and infect every computer
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12
Q

what is an IP address?

A

INTERNET PROTOCOL ADDRESS
- routes the individual packets from one IP address to another
- every computer in the world has an internet protocol address
- they are four 8-bit numbers separated by dots

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13
Q

what is a circuit switching network?

A
  • when you make a telephone call, a dedicated connection is set up between you and that one person - works for calls but there aren’t enough lines for the billions of people sending data via the internet - solved by packet switching
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14
Q

what is packet switching?

A
  • files are broken up in to equal data packets and each packet is given a header
    - the packets will flow through the internet via different routes
    - each packet is marked with a packet number so it can then be put back together by the receiver
  • the recipient then re-orders them
  • each packet is checked for errors
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15
Q

what is contained in a packet header?

A
  • the IP address it is going to
  • the IP address it has come from
  • sequence of the packets
  • number of packets in communication
  • error checking data
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16
Q

what is a data packet?

A

a small chunk of data

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17
Q

how are packets reassembled?

A

the recipient re-orders them by packet number and each packet is checked for errors

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18
Q

what is a node?

A

computers/servers on a network

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19
Q

what is a NIC?

A

NETWORK INTERFACE CARD
- built into every every networked device (wired and wireless)
- most modern phones and computers have the NIC incorporated into their motherboards
- provides a computer with a dedicated, full-time connection to a network

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20
Q

what is a MAC address?

A

MEDIA ACCESS CONTROL
- identifies a device to other devices on the same local network
- assigned to each NIC by the manufacturer
- a device may have more then one MAC address if it has both an ethernet and wifi connection
- smartphones have two: for wifi and bluetooth
- every unique device has a unique MAC address - 2^46 possible addresses

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21
Q

what is the difference between an IP and MAC address?

A
  • IP - the geographical location of a device can be determined by its IP address. if you change location the IP address will change
  • MAC - the MAC address of an NIC is unique and never changes
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22
Q

what is a router?

A
  • looks at the destination of the packets of data and sends them to the network that is the closest to their destination
  • home router will route packets within the home LAN and the internet
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23
Q

what is a switch?

A
  • switches connect each node (computer) in a network and they know all the MAC addresses
  • when a packet arrives, they send it to the correct computers
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24
Q

what is a hub?

A

will send the data to all the connected computers

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25
Q

what is wireless transmission?

A

uses radiowaves for communication but is susceptible to interference from objects and other devices

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26
Q

what is a wireless network?

A
  • they connect using wifi
  • broadcast using radiowaves
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27
Q

what is a WAP/AP?

A

WIRELESS ACCESS POINT
- a device that allows wireless devices to connect to a wired network using wifi
- usually connects to a router via a wired network

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28
Q

what is a wireless NIC?

A
  • built into every networked device capable of connecting to a wired network
  • eg. wireless devices: PCs, smartphones, wireless speakers
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29
Q

advantages of wireless networks

A
  • no need to lay cables
  • easy to connect new devices
  • devices can be portable within the range of the access point
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30
Q

disadvantages of wireless networks

A
  • less reliable than wired networks
  • connection can be very slow if many devices try to use the same AP
  • connection speed reduces further from the access point
  • can be less secure than wired
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31
Q

what is a topology?

A

the way in which parts of a system/network are connected

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32
Q

what are the two types of topologies for networks and LANs?

A

star and bus

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33
Q

what is a star topology?

A

computers and other devices (nodes) are all connected to a central switch

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34
Q

advantages of a star topology

A
  • faster data transfer to the hub as each wire isn’t shared with other computers
  • if one cable fails the others aren’t affected
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35
Q

disavantages of a star topology

A
  • requires additional hardware such as the central switch and network cables
  • if the central switch fails the whole network goes down
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36
Q

what is a bus topology?

A
  • computers and other devices are all conected to a central coaxial cable
  • terminators are placed at each end to absorb signals and to prevent them reflecting down the cable
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37
Q

advantages of a bus topology

A
  • less cable so cheaper to install
  • easier to add more devices as they only need to connect to the central cable
38
Q

disadvantages of a bus topology

A
  • single cable shared by many devices so there may be ‘collisions’ of data if sent at the same time
  • if cable is damaged, whole network fails
  • any device can view all data on the cable: creating a security risk
39
Q

what additional hardware is required to connect a stand alone computer to a LAN?

A
  • NIC in the device
  • switch/hub that connects together all the devices on the LAN
  • modem required to connect to the internet (usually combined with a router to form one device)
  • router needed to route packets towards their destination
  • WAP connects the wireless devices to a network
40
Q

what is ethernet?

A

a family of standard local networking ‘protocols’
- describes how devices should format data for transition between nodes on the same network
- nodes wait until the connection is quiet before attempting to transmit
- two nodes attempting to transmit simultaneously will stop and each wait a random period before reattempting

41
Q

what is ethernet transmission?

A
  • divides data in to frames and each frame contains source and destination addresses and error checking data
  • frames are broadcast to all nodes but only the inteded recipient opens the frame (so the rest is discarded)
  • frames which are detected to have errors are dropped or resent
42
Q

what kind of cables are used ethernet?

A
  • star: twisted copper cables
  • bus: coaxial cable
43
Q

advantages + disadvantages of using a copper cable

A

+ adequate speed for low bandwidth applications
+ low cost cable, with cheaper equipment

  • signals affected by electrical interference
  • significant loss of signal over distance - usually 100m
44
Q

advantages + disadvantages of using a fibre optic cable

A

+ very fast connection with a greater bandwidth
+ signals travel as light waves so cannot be attracted by stray EM signals
+ less loss of signal strength - usually 1km +

  • higher cabling and equipment cost
44
Q

advantages + disadvantages of using a fibre optic cable

A

+ very fast connection with a greater bandwidth
+ signals travel as light waves so cannot be attracted by stray EM signals
+ less loss of signal strength - usually 1km +

  • higher cabling and equipment cost
45
Q

what is bluetooth?

A

a wireless method of connecting devices together over a short distance
- radiowaves at 2.4GHz
- devices usually with 10m of each other

46
Q

how does pairing work?

A
  • persistent link made between the two devices so that data can now be communicated between the devices
  • device can ask for a passkey in order to pair it - greater layer of security
  • passkeys entered only once and then the device is remembered
47
Q

what are network security methods?

A

methods which improve the network’s level of security

48
Q

what are two network security methods?

A

authentication, encryption

49
Q

what is authentication?

A

checking that the cimputer and user are allowed to access content
- commonly done using a username and password

50
Q

what is encryption?

A

encoding of data so that it can no longer be easily understood [converting plaintext to ciphertext]

51
Q

why do people use encryption?

A
  • any data that is transmitted over a network can be intercepted (read and understood) unless measures such as encryption are taken against it
  • data can’t be read easily
52
Q

what is plaintext?

A

the original message to be encrypted

53
Q

what is ciphertext?

A

the encrypted message

54
Q

what is a key?

A

a sequence of numbers used to encrypt or decrypt data, often using a mathematical formula

55
Q

what is the encryption algorithm?

A

the formula for encrypting plaintext
- two inputs: plaintext and a secret key

56
Q

what are the two encryption techniques?

A

private key, public key

57
Q

what is private key?

A

a single key is used to encrypt and decrypt a message and data must be given to the recipient of your message to decrypt the data [SYMMETRIC]

58
Q

what is public key?

A

two keys are used - a public key to encrypt and a private key to decrypt, which is more secure because you never have to send or reveal your decryption key [ASYMMETRIC]

59
Q

what is the caesar shift cipher?

A
  • each letter is replaces by a letter n positions further on in the alphabet
  • n is the key to encrypt AND decrypt the message [symmetric encryption]
  • the most basic and insecure type of encryption
  • shift → 3 means each letter of the code has been shifted to 3 letters ahead of it
60
Q

why is encryption used in networks?

A

wifi, ethernet and fibre optic cables are also vulnerable to eavesdroppers as signals can be listened to from a distance

61
Q

what are the three wireless encryption standards?

A

WEP, WPA, HTTPS

62
Q

what is WEP?

A

WIRED EQUIVALENT PRIVACY
- older method of encryption that should no longer be used to protect home router

63
Q

what is WPA?

A

WIFI PROTECTED ACCESS

64
Q

why is HTTPS used as a mode of encryption?

A

should be used for websites as it encrypts data sent to and received from the site

65
Q

what is strong and weak encryption?

A
  • strong when the useful lifetime of the encrypted data is less than the time taken to break the code
  • weak when the code may be broken in time to use the information but it wouldn’t be worth the effort
66
Q

how does a firewall work?

A
  • separates a trusted network from an untrusted one (the internet)
  • data is sent around a network in small packets and these packets are checked to see their destination and where they came from
  • packets that don’t match filtering rules are dropped - therefore packets from malicious computers can be detected
67
Q

where can firewall be run?

A
  • can be run on dedicated hardware or as software
    1) can be built into hardware as a dedicated unit
    2) built into other devices such as a home wifi router
68
Q

what does a firewall do?

A
  • constantly monitors incoming and outgoing network traffic
  • decides whether to allow or block traffic based on the set security rules
  • prevents many possible ways that an attacker may gain access to a network
  • can block certain malicious computers by filtering packets from a certain IP address
  • port blocking: can prevent access to certain ports on the network
69
Q

what is MAC address filtering?

A

can block a specific device or only allow approved devices via their MAC addresses
- MAC is a unique hex numver assigned to to all NICs
- a wireless router can be configured to block access to specific devices identified by their MAC address

70
Q

what is a protocol?

A

a set of rules that governs transmission of data.

71
Q

what is HTTP?

A

HYPERTEXT TRANSFER PROTOCOL
- accessing and reviewing web pages via the internet - writen in html - protocol requests a webpage from server and then it reponds

72
Q

what is HTTPS?

A

secure HTTP
encrypts the information so it can’t be understood by an eavesdropper
- used by bank websites, online shops and social networks

73
Q

what is FTP?

A

FILE TRANSFER PROTOCOL
used for sending or receiving files to or from an FTP server
eg. a graphical interface

74
Q

what is POP?

A

POST OFFICE PROTOCOL
- downloads every new message to the local device, meaning they are no longer available on the server

75
Q

what is IMAP?

A

INTERNET MESSAGE ACCESS PROTOCOL
- they leave the messages on the server and can be accessed by multiple devices - only removed if deleted by the user

76
Q

what is SMTP?

A

SIMPLE MAIL TRANSFER PROTOCOL
- software sends email to SMTP server used - the mail server relays this message via ‘mail relays’ - email arrives at destination server
used by email softwares: outlook, gmail

77
Q

what is TCP?

A

TRANSMISSION CONTROL PROTOCOL
- breaks up messages sent over the internet into small packets - reassembles the packets at the other end - detects errors//resends lost messages

78
Q

what is UDP?

A

USER DATAGRAM PROTOCOL
- maintains an open data connection to send a stream of packets, without checking that the packets are correctly sent
used in online gaming, video streaming

79
Q

how are emails sent?

A

email sent to a mail server (via SMTP) → forwarded by other SMTP → stored at its destination mail server → user’s computer uses POP or IMAP to access the email

80
Q

what is the TCP/IP protocol stack?

A

four layers which enable communication on the internet

81
Q

in which order do the layers work to SEND data?

A

application → transport → internet → link layer

82
Q

in which order do the layers work to receive data?

A

link → internet → transport → application
1) link layer removes MAC address + passes packets up to the internet layer

2) internet layer removes the IP addresses + passes the packets up to transport layer

3) transport layer reassembles packets + passes it to application layer

4) application layer uses the correct protocol to correctly display the data

83
Q

what does the application layer do? and which protocols function here?

A
  • applications such as email clients and web browsers create data to send in this layer
  • SMTP, FTP, HTTP
84
Q

what does the transport layer do? and which protocols function here?

A
  • creates the connection between two host computers - the two agree the communication settings and the size of packets to be sent and received - data then divided into packets and given a packet number - packets reassembled by transport layer + lost packets resent
84
Q

what does the transport layer do? and which protocols function here?

A
  • creates the connection between two host computers - the two agree the communication settings and the size of packets to be sent and received - data then divided into packets and given a packet number - packets reassembled by transport layer + lost packets resent
    TCP, UDP
85
Q

what does the internet layer do? and which protocols function here?

A
  • responsible for routing packets - the source and destination are wriiten on the packets for transmission
    routers, IP
86
Q

what does the link layer do? and which protocols function here?

A
  • where the physical hardware is located: NIC (network interface card), cables + wifi, OS device drivers
    MAC (media access control), ethernet, wifi, OS device drivers work here
87
Q

what are the advantages of layers?

A
  • layers are self contained - the functionality of one layer won’t affect the other
  • provides interoperability between providers and systems as different hardware or software operates on a particular layer
  • senders and receivers using different software and hardware can communicate using the same layer protocols
88
Q

what is the difference between TCP and UDP?

A

UDP does not check each packet and maintains an open connection

89
Q

what is the difference between POP and IMAP?

A

POP downloads the message from the server so it isnt there anymore whereas IMAP downloads only a copy of the message from the server so that the same email can be accessed from multiple devices

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