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  • Protocols
    • Communications Protocol
      • Standard set of rules used to ensure the proper transfer of data between devices.
        • Devices may differ in transmission speeds/ character sets/ error detecting methods/ security levels.
          • Enables different devices to communicate using the same rules/ standards.
      • Protocols exist that specify the format of the data, and the signals to start, control and end the transfer.
        • Many current protocols have been specified by the United Nations Communicate committee, the ITU.
      • Enables different devices to communicate using the same rules/ standards.
    • Open Systems Interconnection
      • Enables manufacturers to design equipment and software for a particular layer.
        • Consists of an abstract model of networking and a set of specific protocols.
          • Has 7 layers and each layer deals with a specific functionality.
      • Application Layer
        • - Presents information/ data to the end user.
        • - Deals with functions such as data transfer
        • - Messaging
        • - distributed databases
        • - operating system functions
        • - end user interface
        • Interacts with the presentation layer.
      • Presentation Layer
        • - presents data for the application layer.
        • - defines how 2 devices should encode, encrypt and compress data so it can be recieve correctly on the other end.
        • - takes any data transmitted by the application layer and prepares it for transmission over the session layer.
      • Session Layer
        • - creates communication channels, called sessions between devices.
        • - responsible for opening sessions, ensuring they remain open which data is being transferred and closing them when communication ends.
        • - also can set checkpoints during data transfer. If the session is interrupted, devices can resume data transfer from the last checkpoint.
      • Transport Layer
        • - takes data transferred in the sessions layer and breaks it into "segments" on the transmitting end.
          • - responsible for reassembling the segments on the receiving end, turing it back into data that can be used by the session layer.
        • - transport layer carries out flow control, sending data at a rate that matches the connection speed of the recieving device, and error control, checking if the data was recieved incorrectly and if not, requesting it again.
      • Network Layer
        • - breaking up segments into network packets, and reassembling the packets on the recieving end.
        • - routing packets by discovering the best path across a physical network.
          • - the network layer uses network addresses (typically IP) to route packets to a destination node.
      • Data Link Layer
        • - deals with functions such as error detection and error correction.
          • - creating and synchronising data blocks.
            • - converting each outgoing packet into a series of bits.
              • - interacts with the Network/ Physical layers.
      • Physical Layer
        • - responsible for the physical cable or wireless connection between network nodes.
          • - defines the connector, the electrical cable or wireless technology connecting the devices.
            • - responsible for the transmission of the raw data, which is simply a series of 0s and 1s, while taking care of bit rate control.


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