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Flashcards

Internet and commmunication technologies

fiery Barbarian Computer Science Year 10 English 61 cards

Cards in this deck (61)

  1. 1Data transmissionCommunicating of data between one device and another
  2. 23 types of data transmission- Simplex data transmission
    - Half - duplex data transmission
    - Full Duplex transmission
  3. 3Simplex data transmissionOne direction transmission only (Printing)
  4. 4Half duplex data transmissionBoth directions can transmit data, but not at the same time (e.g. walkie talkie)
  5. 5Full duplex data transmissionBoth directions can communicate simultaeneously (e.g phone call)
  6. 63 factors that need to be considered when transmitting data- Direction of data transmission
    - Method of transmission
    - Method of synchronisation
  7. 7BandwidthThe amount of data that can be transmitted in a fixed time normally 1 sec. It's measured in bps. Bandwidth is not the speed of a connection it is the capcity of the connection.
  8. 8Parallel communicationMultiple wires running parallel to each other, and can transmit data on all the wires simultaenously.
  9. 9Serial communicationUses a single wire to transfer the data bits one at a time.
  10. 10Serial v Parallel communicationSerial is used for longer distances and shorter for parallel. When transmitting at the same frequency parallel is faster.
  11. 11USBUniversal serial bus is an asynchronous serial data transmission method. A USB consists of a four wire shielded cable: two for power, and two for data transmission.
  12. 12Asynchronous data transmissionThis is used in transmission where data is sent in irregular intervals. Data is sent in an agreed bit pattern with control bits to prevent data mixing up. E.g. Keyboard
  13. 13Synchronous data transmissionThis is when there is a continuous stream of data accompanied by the timing signal which is synced between the sender and receiver. The bits are counted and reassambled at arrival. Thi sis a faster than Asynchronous.
  14. 14BItrateMeasures amount of data transferred in a fixed time rate.
  15. 15Difference between bandwidth and bitrateBandwidth is theoretical capacity, whilst bit rate is the rate of the message being transmitted
  16. 16Ways of error checking- Parity bit (1D)
    - Parity block (2D)
    - Checksum
    - Cyclic redundancy check
  17. 17Parity bitData is sent in bytes which include 7 bits of data and a parity bit.
    - The parity scheme can be either odd or even
    - An even parity scheme would mean tha there should be an even number of 1's and for an odd an odd number of 1's
  18. 18What is wrong with parity bits- It's hard to detect erros as data bits can interchange.
    - Parity bits have a major flaw because it's 1D so if the sequence gets changed around or flipped it can't be determined.
  19. 19Parity blocks solution to flaws in parity bitsA parity byte is added to transmission instead of a bit. Adding a second dimension, i.e. x and y.
  20. 20LANLocal area network is a collection of computers connected together within a small geographical area or building.
    - LANS can be arranged in diff ways called topologies.
  21. 213 types of devices on a LAN- Connected devices
    - Clients/ Servers
    - Transmission mediums (cables + wireless)
  22. 223 main topologies- Ring, star and bus
  23. 23MACMedia access control is a unique number for a device. It can't be changed and is assigned by the manufacturer. 48 bits long and in hex.
  24. 24Hubs- A device that sits at the center of a network and is connected to clients
    - Designed to transmit data it receives to all connected devices even if MAC addresses are included
    - It's cheaper than switches
    - Lack of security and one communication at a time.
  25. 25Switches- Far better and modern alternative for a hub
    - It sits in the center of a network that is connected to all clients
    - A switch only transmits data to the designated MAC address on the transmission.
    - Widely avaialble, More secure, Greater speed and multiple transmissions can be done at once
    - Costly and complex.
  26. 26Bridges- Connect two LANS together: wireless, wired or both.
    - Only 2 ports one for each LAN
    - Needs a MAC address to send to the exact LAN and client like a switch
  27. 27WANWide area network spans over vast geographical locations. The internet is a WAN.
  28. 28IP addressWhen a device connects to the internet (and LANS) it is given an IP address which is unique and used to identify the device as long as it's connected and active on the network. It is 32 bits long and can be altered.
  29. 29Routers- Devices that forward traffic between different networks
    - They inspect packets and more them accordingly to the fastest
  30. 30Modems- Normally integrated in a router. It converts analogue signals to digital.
  31. 31What packets inlcude in transmissionMessage size, recipient address, error checking info if any, data, etc.
  32. 32TCP/IP- A protocol is a set of rules that we agree to follow attempting a particular action
    - A TCP/IP is the protocol computers follow to transmit data error free
  33. 33Structure of TCP/IP- Files can be broken into smaller ones
    - Computer are able to act as a go between for transmission
    - When received it is check and confirmed if the transmission is a sucess
    - If a packet is corrupt or missing a resent can be asked.
  34. 34HTTP- Hypertext transfer protocol is a set of rules that must be obeyed when using the world wide web.
    - It determines how computers can request webpages and how serves can respond to those requests
    - The s in Https is referring to secure. It is slower than HTTP so is only used if is sensitive data is involved.
  35. 35URLs- Uniform resources locators are what we recognise as website addresses
    - They represent IP addresses and are used because IP addresses are hard memorise
    - When typing a URL a browser mus translate it to an IP address. This is done through Domain name servers.
  36. 36Cookies- Small files downloaded to a computer when a website is visited
    - File is stored by browser and be requested when website is visited
    - Cookies provide a variety of functions
  37. 37Static IPIP that don't ever change
  38. 38Dynamic IPMost devices use this as they are assigned to an address when connectied to a network and they change over time.
  39. 39DNSDomain name system translate a URL into an IP
    - It is decentralised so no one DNS server has all the info
    - It is hierarchical
    -In the system there are clients, DNS resolvers and domain name servers
    - It is important because without it we won't reach websites
  40. 40CachingWhen a URL is successfully translated in to an IP address it'll be cached
    - DNS resolvers will cache the result for the client to use
    - Cached results have a time to live and will be deleted
  41. 41TCP/IP Stack4 layers. Application, transport, internetworking layer, and network interface layer
  42. 42TCPA transmission protocol has 3 layers
    - It first established a connection to monitor packets
    - TCP divide messages into segements
    - A segment contains info abt which application it's for
    - Makes sure data isn't missing and is in right order
    - TCP helps determines the speed that two hosts communicates so both can cope
    - TCP is used where missing info and errors can't be tolerated.
  43. 43TCP Handshake- A handshake is how two computers make a connection and manage transmission of packets
    - A TCP does this by sending a SYN, SYN/ACK, and ACK. This is doen to send data acknowledge it and acknowledge that it has been acknowledged and shut the connection.
  44. 44UDPUser datagram protocol is a 3 layer protocol
    - Doesn't establish a connection
    - Divides messages into datagrams
    - Datagrams contain info abt which application the datagrams are for and error checking
    - UDP doesn't resent packets
    - UDP is used when we can tolerate errors and speed is more important.
  45. 45Encryption- Concept of modifying data so that it becomes scrabmbled and can only be decoded by a key
    - The key is to used to encrypt and decrypt
    - Longer the key harder to guess
    - Encryption is converting PLAIN TEXT to CIPHER text.
  46. 46Symmetric encryption- This encryption is where a key is generated, and the same key is used to encrypt and decrypt data.
    - The key is much shorter than asymmetric and faster
    - Key length also affects the size of encrypted text. Bigger keys lead to bigger file sizes but the're harder to crack
  47. 47Asymmetric encryption- This is where there are 2 diff keys
    - A public key is used to encrypt the message but can't be used to decrypt it
    - Keys are created in pairs; private and public
    - Private key used to decrypt
  48. 48Network interface controller- Allows for a connection with a network as it packages internal parallel data into bit streams so it can be used for serial transmission over long distances.
  49. 49Middle man in encryption- A middle man is when an unwanted device intervenes the communication between two clients when they exchange keys in order to understand what is being sent
    - The devices don't realise and they are sending data to the middle man who reads it and moves it along so they won't notice.
  50. 50Fix to the man in the middle problem- We use a digital certificate which is issued by a third party which confirms that the public key is authentic
    - The end goal is to have a secure connection
  51. 51How do SSL/HTTPS use both types of encryption- SSL - secure socket layer
    - SSL is a protocol used by the HTTPS protocol to encrypt data in a way that it can't be read if intervened
    - This is done by using both types of encryption
    - The SSL certificate (form of a digital certificate) is sent through asymmetric encryption to the client along with the server's public key. The client uses the public key of the host server to encrypt the session key and after that a symmetric encryption is formed. This is done to save time.
  52. 52Checksum- Uses all the numbers to create a sum which the receiver also carries out and compares it to the sender. This allows the receiver to know if the bits are in the correct arrangement
  53. 53Possible causes for data lossCrosstalk, theft, congestion, computer viruses
  54. 54DDoS attack- Distributed Denial of Service
    - This is where a server is bombarded with fake clients, which leads to connections being half opened. This is because fake ip addresses are used and the handshake is not completed.
    - Eventually, the accumulation of far too many half open connecitons causes the server to stop working
    - A fix would be to have a timeout and close half-open connections or have a whitelist of IP addresses
  55. 55Social engineering: Phishing- A fradulent message sent in order to get the recipient's sensitive information
  56. 56Social engineering: Pharming- Malicious software downloaded which alters the information the computer has on a URL and leads it to a fake website to get the recipient's sensitive information.
  57. 57Automatic request query (ARQ)- This is when an acknowledgement hasn't been received and the two devices are in a deadlock
    - Therefore, in the handshake there is an agreed time interval for which if there is not acknowledgment it is resent
    - This prevents data loss
  58. 58Trojan Horse virus- Malware that is hidden in a program normally downloaded from a message
    - The trojan horse virus allows the attacker to do anything from turning on the camera to recording keyboard movements.
  59. 59Keylogger- Malware that records keyboard inputs
  60. 60Ransomware- Malware that is used to threaten publishing one's sensitive data as a ransom.
  61. 61Outline the steps in the process that takes place when you enter a URL into a browser, in order for a web page to be displayed- Once the URL is entered the browser checks its webcache, the computers cache and ISP cache in order to find a matching IP address. If none have been found it goes to the DNS server where all IP addresses are stored.
    - Once the IP address has been obtained a secure connection followed by a TCP/IP handshake is carried out.
    - The server replies with a HTTP response including the URL's resources like CSS, Javascript, HTML and the browser assembles it together and displays it.

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Year 10 Computer Science Flashcards on Internet and commmunication technologies, created by fiery Barbarian on 13/11/2021.
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