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1.3.2 Networks, protocols and layers - Coggle Diagram

- - - - If all packets are present, using the sequence number of each packet to re-assemble the message
      - Spotting missing packets and requesting them to be re-sent
      - Fixing any errors (if possible) or requesting that the packet be re-sent
      - Examining each packet for errors by using the extra information that was added to it
    - - Adding a sequence number to each packet so the message can be re-assembled
      - Adding extra error-correction information, so errors can be spotted and fixed
      - Dividing the message into packets
  - - - Accept data packets that have its own address attached
      - Ignore all data packets that do not contain its own address
    - - Add it own address to indicate where it came from
      - Add the destination address to each data packet
  - - - The email remains on the server even after being downloaded to the device
      - IMAP allows you to
        
        Set flags on emails showing whether they have been viewed, replied to, deleted
        
        Access emails on multiple devices
        
        Synchronisation across devices
        
        It allows complex searches to be carried out based on subject, headers and so on
        
        It can handle more than one mail box
        
        You can choose whether to download just the headers, full body or not to download attachments
    - - Used by the mail server itself to send and receive emails from all other mail servers across the internet
    - - Allows emails to be downloaded and /or deleted from a mail server and viewed offline by an email client
      - disadvantages
        
        It can only handle one mailbox
        
        Messages, once downloaded, are removed from the email server and cannot later be viewed by other devices
        
        It does not support complex searches of emails on the server
- - - - Sending data
      - Security
      - Network switch
  - - - An IPv4 address is presented as four decimal numbers separated by dots 198.234.034.002
- - - - The data being sent
      - The MAC address of the device sending the packet
      - The MAC address of the device receiving the packet
      - Error checking bits
    - - Check that the cable is unused before sending out a data packet
      - If two packets do collide then each device must wait a short random time before re-sending their packet. This lessens the chances of it happening again.
  - - - Security
      - Limited range
      - Limited connections