Computing

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  • Created by: sharb
  • Created on: 10-03-20 12:55
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  • Protocols
    • Topologies
      • In a bus network all the workstations, servers and printers are joined to one cable (the bus). At each end of the cable a terminator is fitted to stop signals reflecting back down the bus.
      • In a ring network each device (workstation, server, printer) is connected to two other devices - this forms a ring for the signals to travel around.
      • In a star network each device on the network has its own cable that connects to a switch or hub.
      • In a mesh topology there is no central connection point. Instead, each node is connected to at least one other node and usually to more than one. Each node is capable of sending messages to and receiving messages from other nodes. The nodes act as relays, passing on a message towards its final destination.
    • Packets
      • Transmissions over a network can be extremely large in size.
      • messages are broken up into very small pieces, called packets.
      • Header - this includes the sender's and recipient's IP addresses, the packet number, the total number of packets the message contains, plus the details of any protocols used
      • Payload - this is part of the actual message itself
    • Network security
      • Anti-virus software on all computers
      • Firewalls block unexpected connections form connecting to the computers
      • Secure passwords protect important information
      • Access levels stop certain files from being accessed by everyone
      • Applying encryption to files may make them hard to understand if read by something that can't decrypt them
    • Network hardware
      • A router can form a LAN by connecting devices within a building. It also makes it possible to connect different networks together.
      • A modem converts digital signals from a computer to analogue signals that are then sent down the telephone line.
      • A hub broadcasts data to all devices on a network. This can use a lot of bandwidth as it results in unnecessary data being sent
      • A bridge is used to connect two separate LAN networks. A computer can act as a bridge through the operating system. A bridge looks for the receiving device before it sends the message.
      • A switch performs a similar role to a hub and a bridge but is more powerful. It stores the MAC addresses of devices on a network and filters data packets to see which devices have asked for them.
      • MAC addresses
        • Every piece of hardware on a network has a unique MAC address.
          • This is embedded in the hardware when the product is made in the factory, and the user cannot change it.
            • A MAC address is made up of 48 bits of data, usually written as 12 hexadecimal characters.
              • NICs enable desktop and laptop computers to connect to a network. NICs are small circuit boards that connect to the motherboard.
                • Smartphones also use a GSM chip to connect to the telephone network.
                • Every piece of hardware on a network has a unique MAC address.
                  • This is embedded in the hardware when the product is made in the factory, and the user cannot change it.
                    • A MAC address is made up of 48 bits of data, usually written as 12 hexadecimal characters.
                      • NICs enable desktop and laptop computers to connect to a network. NICs are small circuit boards that connect to the motherboard.
                        • Smartphones also use a GSM chip to connect to the telephone network.
    • Wifi
      • A wireless connection uses radio signals to send data across networks.
      • Advantages
        • Cheap
        • Not a specific location
        • less disruption
      • A WAN covers a large geographical area. Most WANs are made from several LANs connected together.
    • Ethernet protocol
      • Protocols establish how two computers send and receive a message.
    • Layers
      • In networking, layering means to break up the sending of messages into separate components and activities.
        • Layering allows standards to be developed, but also to be adapted to new hardware and software over time.
    • LANs and WANs
      • A LAN covers a small area such as one site or building, eg a school or a college.
        • A router can form a LAN by connecting devices within a building. It also makes it possible to connect different networks together.
      • A WAN covers a large geographical area. Most WANs are made from several LANs connected together.
    • Client Server
      • This type of network separates computers into servers and clients.
      • A server is a computer that manages and stores files, or one that provides services to other computers on the network. They control the network and allow other computers to share and communicate.
    • Peer to Peer
      • In a peer-to-peer network, all computers have equal status - no computer has control over the network.
      • Peers store their own files, which can be accessed by other peers on the network.
    • URLs/IP addresses
      • Every website address has a URL with an equivalent IP address.
        • When you type in a URL, the ISP looks up the domain name, finds the matching IP address and sends it back
          • The web browser sends a request straight to that IP address for the page or file that you are looking for.
      • The web browser sends a request straight to that IP address for the page or file that you are looking for.

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