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networking,communication and the internet - Coggle Diagram

- - - - Application:
        the application software makes sure the correct protocol is used
        
        Transport:
        The Network layer breaks up the data into packets, numbers them and sorts out routes for them.
        
        Network:
        The Transport layer Adds sender and recipient IP addresses to the packets.
        
        Link:
        The Link Layer adds a MAC address to the package
    - - The internet is mostly a wired network
      - Internet cables pass under oceans to connect to different continents
    - - An ISP is a company that provides its customers with access to the internet.
        
        The largest of these are national internet service providers
        
        National ISP'S Provide internet access to local ISP's, where homes and businesses can buy access to the internet
  - - - Components of a packet:
        
        Senders address
        
        Receiver's address
        
        Packet Contents
        
        Time to live (TTL)
        
        Sequence Number
        
        1 more item...
        
        Holds the number of hops a packet can go through before being dropped
        
        Where the packet holds data being transferred
        
        identifies the receiver
        
        Identifies the sender
    - - They both connect different networks, allowing packets to reach their destination
        
        Routers send packets to their recipient via the
        fastest possible route, this might be the route that involves the lowest number of hops or is the least congested
        
        when two networks use different protocols, packets must be modified so they conform to both protocols, gateways do this by stripping away all info except for the packets contents
  - - - A Domain Name identifies an organisation or individual on the internet, they use alphanumeric characters which make them easy for humans to remember
    - - Internet protocol addresses are assigned to every computer on the internet and every device that communicates on a network
        
        IP Addresses are not easy for humans to remember, which is why domain names are used. domain names map to IP addresses, meaning they are essentially a human friendly representation of an IP Address
  - - - In Symetric encryption, both the sender and receiver share the same private key. This Key is used to both encrypt and decrypt the data, this however is easy to intercept when shared over a network
      - Asymmetric Encryption
        
        Four different keys are used. Each device has a pair of mathematically related keys keys, one is a private key and the other is a public key.
        
        When a message is sent with a public key only the corresponding private key can decrypt it