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Flashcards

A2 IT Networks

Sean Byrne IT AS level English 149 cards

A2 IT Networks

Cards in this deck (149)

  1. 1NetworkA set of computers and devices connected together so they can communicate and share resources
  2. 2SwitchConnect devices on a network
    Network cables connect the device in a network to a switch
    Examines each data packet that it receives and sends it to the desired port
    Cannot distinguish devices as it cannot assign IP addresses by iteself
  3. 3PacketA set of bits which represent data to be transmitted. An IP data packet will include header information and the data being sent. The header information will include the source address, destination address, IP version, and ID number for sequencing
  4. 4HubSimilar to switch but does not examine each data packet that is received; instead, simply transmits each data packet to all connected ports. Can also be classed as a multi-port repeater
    Blast same network traffic to all outbound ports and severely limits speed
  5. 5Wireless access pointConnects Wi-Fi enabled devices to a network. Connected to a switch by cable but it is possible to have it completely wireless. Can send data to a switch or another WAP
  6. 6Wi-FiWireless Ethernet which allows devices on a LAN to connect wirelessly.
  7. 7NICNetwork interface card which connects the motherboard of a device to a network cable. Has a unique MAC address
  8. 8WNICWireless network interface card which enables a device to use Wi-Fi. Can be connected to a non wireless device by using a dongle connected by USB or an expansion card. Has a unique MAC address
  9. 9RouterA switch which can forward data to the correct location in the most efficient manner. Assigns and stores the addresses of all devices connected to it
  10. 10LANLocal area network which connects devices in a single building or area
  11. 11WANWide area network which connects devices that are geographically remote
  12. 12RepeaterAmplifies the signal on a network cable. It is also another name for an active hub. Used when long cable lengths are required and the signal is not strong enough to reach its destination by itself. Can have wireless repeaters
  13. 13GatewayConnects two different types of networks. Typically used as a router to connect LAN to WAN
  14. 14BridgeConnects two LAN's that are physically separate of the same type so that they can communicate with each other.
  15. 15FirewallPrevents external devices from gaining unauthorized access to a computer system. Usually positioned at the gateway. Can prevent certain types of data from leaving the network. Can prevent malicious data packets from entering. Can be software on a computer.
  16. 16ServersA computer on a network which provides resources that can be used by client devices
  17. 17VirusSoftware that replicates itself in order to corrupt data
  18. 18BandwidthThe range of frequencies available for a communication method which determines the transmission rate. Governs the maximum speed that data can be transferred
  19. 19Bit rateThe number of bits that can be transferred per second. This is the actual transmission speed
  20. 20StreamingA method of displaying sound or video without waiting for the whole file to be downloaded. Uses a buffer.
  21. 21Circuit switchingA single communication path which is opened for the duration of data transmission. No other devices can transmit data using that path. When complete, it is then open to other data transmissions
  22. 22Packet switchingData that is broken down into packets that are sent through different routes and reassembled by the recipient. Includes header data which identifies the source and destination, some of the data and error control bits.
  23. 23Message switchingA method of transmitting data through intelligent node. Transmits all of the data without a predefined route. Uses a method known as "store and forward"
  24. 24InfaredA communication method used by most remote control devices. Transmits electromagnetic radiation just past the red end of the visible light spectrum. Does not have a high bandwidth and is affected by sunlight
  25. 25Fibre opticA fine strand of glass that transmits data as light beams. Lots of strands means lats of data being transmitted at once. Flexible means cables can be bent. Not affected by electrical interference. Used over large distances
  26. 26LaserAn intense beam of light used for transmitting data. Can cover large distances. Line of sight necessary. Travels at the speed of light
  27. 27BluetoothA short-range wireless communication standard that uses short wavelength UHDF radio waves and travels in the ISM band at 2402-2403.85 MHz.
  28. 28BiometricUnique physical characteristics of a person that can be used by computers for identification purposes
  29. 29RFIDRadio-frequency identification. The RFID reader will be continuously sending interrogation signals through its antenna to identify the location of any RFID tags
  30. 30NFCNear field communication i.e. close proximity RFID chips. Phones can emulate NFC tags to read or scan
  31. 31ProtocolA set of rules that ensure data is transferred between devices correctly
  32. 32MACMedia Access Control
    Sender MAC address will change during transmission to the most recent device each time the data packet passes through a device such as a router. The receiver MAC address will change to the address of the next device on its route to the final desitnation
  33. 33File serverA file servers role is to make files available for users on the network. The files can be individual files stored for their own user or shared between users depending on permissions
  34. 34Print serverDeals with all the print jobs on a network. When a client computer sends a request for printing, it will be put in queue. Print server will then deliver each print job in turn to the printer
  35. 35Mail serverReceives and sends all emails for an organisation. Can be part of LAN or WAN. Incoming emails are checked for viruses, phishing or spam. When a user sends an email, the mail server will either send it to another user in the network or to the internet.
  36. 36A proxy serverDeals with requests to the internet and sits between the LAN and the gateway. It will check if each request is allowed and will filter out unwanted requests. It will also store the web pages cache in order for it to load faster in the future
  37. 37BufferA region of physical memory storage used to temporarily store data while it is being moved from one place to another
  38. 38Store and forward (Message switching)Where data is sent to a network node at a time and is temporarily stored before being sent to the next node
  39. 39Uses for BluetoothCar audio system for hands-free communication
    A headset for hands free communication
    Bluetooth smartwatches and phone features
    Sending and receiving biometric data
    Streaming videos to a bigger display
    Streaming to Bluetooth speakers
    Transferring files from one phone to another or other Bluetooth connected device
  40. 40Uses for WiFiConnection of portable devices
    Smart TV that use the service of the internet
    Printers that can connect wireless
    Casting a devices screen to another screen
    Smart home devices
  41. 41Advantages of BluetoothCan be used to network devices together in small area with low bandwidth
    Doesn't require radio frequency license
    Common standard
    Very little power to operate
    Doesn't require line of sight
    Can set up security methods
    Can allow for more than one device to transmit on the same frequency
    Interference resistant
  42. 42Drawbacks of bluetoothLimited data transfer rate
    Short range
    Limit of how many device can connect at a time ( 8 devices)
  43. 43Advantages of WiFiCan connect without the need of cables which can be expensive
    Devices can be located anywhere within the range
    International standard and doesn't require a line of sight
    Mobile phones can save their 4G by connecting to the WiFi
    Not that much slower than wired connection
  44. 44Drawbacks of WiFiRange of WiFi can be restricted due to objects
    Speed depends on bandwidth and the number of connected devices
    Hackers no longer need a physical connection to access the network
    Sufficient encryption is required
  45. 45Uses of RFIDMonitor the location of parcels from a distribution warehouse to the delivery point.
    Wireless key cards that are used to unlock doors and can be part of an employee's ID badge.
  46. 46Uses of NFCMake contactless payment using a credit or debit card
    Secure method of RFID
    Doesn't require a line of sight
    Prevents accidental transcations
    Does not require somebody to manually scan the tag
  47. 47The two scenarios where bandwidth is importantAccessing content within a time limit
    Accessing content within real time
  48. 48Cables (copper)Main method used for connecting LAN.
    Most common form is known as un-shielded twisted pair or UTP.    Cables (copper)
  49. 49Drawbacks of using cablesNo earth wire, which results in loss of data packets at high frequencies
    Only suitable up to 100 m
    Only frequency available by copper
    Electrical interference can cause loss in data packets
  50. 50STPShielded twisted pair
    They include a metal shield around each twisted pair and an earth wire for when high bandwidths are required
  51. 51Wireless (communication media)Less frequencies are available for WiFi than using Ethernet cables. Susceptible to interference from other wireless devices. Obstacles can reduce the strength of the wireless signal
  52. 52OpticalFibre optics are not susceptible to electrical interference. Less likely to lose data packets and the total bandwidth available is higher than copper cables
  53. 53A communication protocolA set of rules that ensure data is transferred between devices correctly. Required so that a variety of devices and applications can communicate together correctly
  54. 54What a protocol includesMethod of addressing to use
    Type of error checking to be used
    How sending devices indicate the start and end of a message
    How a receiving device will confirm it has received a message and any data compression methods used
  55. 55Abstraction layersThe ISO published a layered model that defined a framework that put protocols into seven different layers known as OSI
  56. 56The different layers in abstraction layersPhysical layers
    Data link layer
    Network layer
    Transport layer
    Session layer
    Presentation layer
    Application layer
  57. 57Physical layerDeals with electrical and mechanical operations
  58. 58Network layerHow data is switched, routed and addressed
  59. 59Data link layerDeals with data packets
  60. 60Transport layerEnsures data flows correctly without errors
  61. 61Session layerDefines protocols between applications during a communication session
  62. 62Presentation layerEnsures that data is in a format that can be recognized such as types of image, types of video file and text encoding method to use
  63. 63Application layerDeals with specific types of communication application such as file transfer or email
  64. 64POPPost office protocol defines rules for email client software to to retrieve emails. Part of the application layer of the OSI model
  65. 65How POP worksConnects to an email server, downloads all messages and stores them on the client computer and then delete the messages from the server
  66. 66IMAPInternet message access protocol is an alternative method for email client software to retrieve emails. Part of the application layer of the OSI model
  67. 67How IMAP worksInstead of downloading the email and then deleting the email, its default mode is to leave the email on the server and download a copy to the client. This means that emails can be accessed from another location
  68. 68TCP/IPTransmission Control Protocol/Internet Protocol is the basic communication protocol used on the Internet and in most LANs and WANs. Contains two layers
  69. 69How TCP/IP worksTCP breaks a message down into small data packets that are transmitted and then reassembled at the receiving end. IP deals with the address to ensure that each packet reaches the correct destination.
  70. 70FTPFile transfer protocol is part of the TCP/IP suite and is used to define how computer files should be transferred from one location to the other. FTP is the application layer of the OSI model
  71. 71How FTP worksAllows users to be authenticated by username and password but also has an option for anonymous connectivity. Sets the rule for how a server should respond using ASCII codes, the data format to use, and the mode of data transfer
  72. 72HTTPHypertext Transfer Protocol is also part of the TCP/IP suite. HTTPS is the secure version that encrypts transmissions. HTTP is the transport layer of the OSI model
  73. 73How HTTP worksIs used by web browser to send requests to a web server to view a web page
  74. 74BitTorrent protocolSpecifies how multiple downloads can take place from the same file source concurrently. Several clients (peers) download portions of the file. The peers then connect to each other directly to send receive those portions of the file between themselves. This reduces the required bandwidth by the original host of the file
  75. 75How BitTorrent protocol worksOnly works effectively if there are lots of peers downloading the same file, as without lots of peers there are less opportunities to receive portions of the file.
  76. 76What is a torrentA metadata file which identifies the locations (Uniform Resource Locator) or trackers which coordinate communication between the peers in the swarm.
  77. 77What is a swarmA set of peers that are downloading parts of the file and uploading parts for each other to download on a peer
  78. 78What are seedersClients that have a full download of the torrent and are still making it available to upload to other peers
  79. 79MalwareMalicious software
  80. 80SpywareMalicious software that records what a user is doing on a computer system
  81. 81Unauthorized accessTakes place when a person or device gains access to a computer network without permission. Once a hacker has access, they can read data on the system. This data may be confidential or they might try to destroy it or make changes
  82. 82VirusDesigned to cause damage to data or cause problems to the operation of a computer system. Attach themselves to files on a computer system and are triggered by certain events. Viruses copy themselves automatically to other devices
  83. 83Macro virusesAttach themselves to macros that are part of macro-enabled documents
  84. 84Email virusesViruses that arrive as attachments to emails and are triggered by the user opening the attachement
  85. 85WormsDon't require files to attach to as they create their own executable file. These are unique to networks as they spread automatically throughout the network
  86. 86Trojan horsesMalicious programs that disguise themselves as normal software, but if they are run they will actually cause damage. Often found on websites when a user tries to download some illegal music or films they end up downloading a Trojan instead
  87. 87SpywareSoftware that secretly collects information without the user being aware. Can log user activity including identifying credit card information or usernames and passwords. Spyware can collect data and transmit it to another server
  88. 88DoSDenial of service attack. Designed to send more requests to a server that it can deal with. Easy to launch and difficult to track.
  89. 89Purpose of DoS attackThey are carried out to cause disruption to an organisations network or website and often result in users not being able to use the network and customers not being able to access the website
  90. 90How are website attacks measuredIn requests per second or RPS
  91. 91How many RPS is needed to stop a website50
  92. 92How are network attacks measuredGigabits per second or Gbps
  93. 93How many Gpbs does it need to stop a network20
  94. 94DDoSDistributed denial of service. Uses multiple connects distributed among the internet to overload the target. These are more difficult to defend because they are coming from many different locations
  95. 95Motivations of perpetrators of DoS attacksVandalism
    Activist campaign
  96. 96Data protection act principlesUsed to protect people about whom data is stored aka the data subjects
  97. 97List of data protection principles/Information about the data subjectsUsed fairly and lawfully
    Used for limited, specifically stated purpose
    Used in a way that is adequate, relevant and not excessive
    Accurate
    Kept for no longer than absolutely necessary
    Handled according to people's data protection rights
    Kept safe and secure
    Not transferred outside the European Economic Area without adequate protection
  98. 98Need for data protection actRequired in order to protect data subjects and the information that is held about them. People have a right to know what information is being stored and that is stored accurately
  99. 99How to process data fairlyData subjects must be asked permission for organisations to use data about them. They must also be aware of the purpose of this data. Organisations must only use the data for this purpose
  100. 100What do data subjects expect from organisationsEnough information will be stored as necessary
    Only necessary and relevant data is stored as they have the right to privacy
  101. 101What rights do data subjects expectTheir data to be accurate and up to date
    Have a right to request that any inaccurate data is corrected
    Data subjects have responsibility of informing data users of any changes in personal information
  102. 102What should data users do with data about othersStore it for only as long as necessary
    Keep their data secure
  103. 103SatelliteAn object in space that follows an orbital path
  104. 104GPSGlobal Positioning System which uses satellites to determine the current location
  105. 105How satellites workUses microwave signals to send and receive data
  106. 106LEO satelliteLow earth orbit satellite. 500-1500 km from earth and 40-80 are required for global coverage
  107. 107MEO satelliteMedium earth orbit satellite. 5000-12500 km from earth requiring 8-20 satellites for global coverage
  108. 108GEO satelliteGeostationary earth orbit satellite. Located at 35800 km from the earth and only 3 are required for global coverage
  109. 109Satellite broadbandUsed in areas that are not covered by wireless or wired broadband such as rural areas or deserts. These use GEOs. Not suitable for real time application
  110. 110Methods of suing satellites for broadbandOne-way satellite
    Two-way satellite
  111. 111One-way satelliteSends data for download from the internet to the client and uses a public switched telephone network (PSTN) connection for the client to upload data. This means that uploading data can be very slow
  112. 112Two-way satelliteThis allows the client to upload data directly directly to the satellite as well as to receive data from the satellite. However, this requires more expensive equipment that can transmit microwaves
  113. 113Disadvantage of satellite over fiber optic and ADSLIt is more expensive
  114. 114Advantage of satellite over radio waves and cablesAble to offer far more channels over a large range of frequencies unlike cable where it is limited to where cables are installed or radio where it is dependent on what frequencies are available
  115. 115What users need to watch satellite televisionAn STB (set top box) - this decrypts the broadcast that the dish receives
    Satellite dish - receives from a GEO satellite
  116. 116Why do TV companies use encrypted signalsSo that users have to subscribe to view the content and so cannot be watched by viewers who have not paid. Free-to-air channels are not encrypted
  117. 117Main benefit of satellite televisionAvailable in remote areas. Useful for people who go camping. Viewers can watch television from their neighboring country if needed.
  118. 118Drawbacks of satellite television in urban areasSeen as expensive to initially purchase and set up
    Unsightly
    In severe weather conditions, microwaves may be disrupted
  119. 119TrilaterationWhere three satellites are used to determine the distance between the GPS receiver and each satellite, which allows the exact location to be calculated
  120. 120Diagram of trilaterationDiagram of trilateration
  121. 121Uses for GPSLocating emergency vehicles so they can be sent to location
    Finding nearby taxi for taxi apps and calculating fares
    Tracking people, objects and vehicles
    Geo tagging photos
    Satellite navigation systems
    Treasure hunt games such as Geocaching
    Tracking cycling and running routes
  122. 122Benefits of using GPS in sat navsProvide real time locations on a live map and so drivers can focus on driving more
    If a driver misses a turn, a new route can be calculated
    On computers or phones, sat navs will be regularly updated
  123. 123Drawbacks of using GPS in sat navsWhen inputting a destination while driving, this can be very dangerous
  124. 124Problems of GPSLine of sight required and so finding exact position can be difficult if line of sight is blocked by a bridge
    Signal depends on atmospheric conditions, does not work well in poor weather conditions
  125. 125How GPS navigation systems workSignals from satellite travel by line of sight to navigation device
    Use L1/1575.42 MHz in UHF band
    Satellites are LEO
    Signal contains ID code of the satellite
    Navigation device must lock to 2 satellites to calculate 2D position
    To 4 or more satellites to calculate 3D position
    Use trilateration techniques
    Calculation by finding intersect point by timing the signals from the satellite
  126. 126What does GPS signal containStatus info
    Current date and time from atomic clock in the satellite
    Almanac data about where each GPS satellite is at any point in time
  127. 127How GPS signals can be degradedAtmospheric delays slowing the satellite signal slows as it passes through the atmosphere
    Signal multi path errors as the GPS signal is reflected off objects before it reaches receiver and increases travel time of the signal
    Clock errors in the receiver because the built in clock is not as accurate as the atomic clocks on board the GPS satellite
    Orbital errors of the satellites reported location
    Satellite geometry because the relative position of the satellites at any given time is not ideal for signal reception by the receiver so the satellites should be located at wide angles relative to each other and poor geometry occurs when the satellites are located in a tight grouping
    Intentional degradation of the satellite signal by the operator of the satellites to prevent military adversaries from using highly accurate GPS signals
  128. 128Benefits of packet switchingAllows for each packet of data to travel through the most efficient route of nodes making file transfer much faster
    Contains identification information to be sent to the right place and correctly recombined, means that the data doesn't become corrupt
  129. 129What are the layers TCP/IP are made ofApplication
    Transport
    Internet
    Network
  130. 130What happens at the application layer of TCP/IPPrograms like the web browser your computer interacts with
    Contains protocol such as HTTP for pages or SMTP for emails or FTP for general file transfer
  131. 131What happens at the transport layer of TCP/IPWhere TCP and UDP are
    After application layer gets data from program, communicates with transport layer using ports
    Ports can be assigned to a specific protocol
  132. 132What port does HTTP usePort 80
  133. 133What does TCP/IP use to transmit dataPacket switching
    TCP puts headers onto each packet of data which contains instructions on what order to combine the packets into and contains error checking information
  134. 134What does the internet layer in TCP/IP doThis is where IP is
    Attaches the origin and destination IP address
  135. 135What does the network layer in TCP/IP doHandles MAC addressing so that the data packets go to the right physical machine as well as converting the data into electrical impulses
  136. 136Benefits of copper cables over fibreLess expensive
    Deployed in most places i.e. is available everywhere
  137. 137How copper cables workUses movement of electrons to carry out signals by modulating a waveform at one end and demodulating it at the other end to convert the patterns in the waveform to analog or digital signals
  138. 138How fiber optic worksUses light bursts to carry a signal instead of waves traveling through metal
    Made of highly transparent flexible glass core wrapped in layers
  139. 139Benefits of fiber optic over copper cablesTravels faster
    Signal clearer at further distances
    Immune to EM interference
  140. 140Different methods of Wi-Fi securityWEP ( Wired Equivalency Privacy) which is weak
    WPA which used much longer encryption keys
  141. 141HDLCHigh-Level Data Link Control
    A protocol used used in WAN
    Layer 2 protocol
    Used to connect point to point serial devices
    Performs error correction
    Routers encapsulate HDLC before putting on LAN
  142. 142Frame RelayLayer 2 and 3 protocol
    Puts data into variable sized packets
    Does not include error correction
    Specifies physical and logical link layers
    Used in packet switching
    Used on ISDN
    Used in permanent virtual circuits
    Can provide QoS worth constant bitrate
  143. 143What port does FTP usePort 21
  144. 144What port does smtp usePort 25
  145. 145How does a network router connect a device to the internetHas two or more connections to different networks
    Router reads address information in the packet header:
    to determine destination of packet
    has a routing table
    contains data on all possible routes to groups of addresses
    priorities for connections for handling data packets
    routing tables are dynamic
    directs packets to next router
    direct packets
    Router updates hop count every time it forwards a packet
    when hop count limit is reached packed is dropped
    usually a maximum of 16 hops
    or marked as undeliverable
    so packet does not live forever on network
  146. 146Benefits of FTPFTP achieves full speed as soon as it starts download and can achieve very high downloads speeds
    FTP is sequential download of file sections
    FTP is from one IP connection so is quicker to download of file sections
  147. 147Drawbacks of FTPFTP is not resistant to flash-dot/crowds/website overload/dos
    FTP cannot restart if paused, so if interrupted the download has to be done again
  148. 148Benefits of BitTorrentResistant to flash-dot/crowds/website overload/dos
    Can be paused and restarted
  149. 149What is a DSN serverA server which ISP's will go to use as an index between domain names and IP addresses

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AS level IT Flashcards on A2 IT Networks, created by Sean Byrne on 09/10/2017.
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Sean Byrne
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