Networks and Communications Week 11 General Aspects of Communications

How do IP addresses work?

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  every machine on the internet has a unique IP address (eg: 137.219.117.1)
  
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  each of the 4 numbers are called octets (eight bits for each of the four numbers)   each octet can represent 256 values (0 - 255)
  
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  all the 4 octets are added together to produce a single 32-bit number
  
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  some IPs are special/reserved: 0.0.0.0 (for a default network), 255.255.255.255 (network broadcast to machine on the network), 127.0.0.0 (loopback network testing)
  
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  the octets are also used to define difference classes of networks
  
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  the octets are used in various ways to define the Net & Host components
  
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    Net component - the network that the machine belong to
    
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    Host component - the actual machine
    
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  there are five classes of network:
  
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    class A
    
    • 
      very large networks (16 million hosts)
      
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      1st octet is the Net component, a number from 1 - 126
      
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    class B
    
    • 
      medium size networks (65 thousand hosts)
      
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      1st octet is a number from 128 - 191
      
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      1st & 2nd octets form the Net component
      
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    class C
    
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      small sized networks (254 hosts)
      
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      1st octet is a number from 192 - 223
      
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      1st, 2nd, & 3rd octets form the Net component
      
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    class D
    
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      used for multicasts (when a node sends a packet addressed to a special group address)
      
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      can access 268 million IP address
      
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      the 32-bits of the IP number always start with 1110
      
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    class E
    
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      the experimental class
      
    • 
      can access 268 million IP address
      
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      the 32-bits of the IP number always start with 1111