Request Service                  Provide Service
                          v.s. peer-to-peer model
     Network Protocols =
     agreed-upon ways in which computers exchange information
     
      Syntax: structure or format of the data
     
      Semantics: meanings
     
      Timing/Procedrue: when data should be sent and how fast it can 
     be sent.
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                                     LAN
                                          MAN
                                      WAN
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   Internetwork
   Internetworking devices: bridges, routers, brouters, gateways
    
       Figure  1-4 The Internet
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  The Internet:
  A collection of networks and routers that span many countries and uses the 
  TCP/IP protocols to form a single, cooperative virtual network.
   
  Intranet: connection of different LANs within an organization.
   
  Main players in the Internet:
  Started by U.S. research/military organizations:
  (D)ARPA: (Defense) Advanced Research Projects Agency
                   funds technology with military usefulness
   
  DoD: U.S. Department of Defense
             early adaptor of Internet technology
   
  NSF: National Science Foundations
             funds university research
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     Today:
     National backbone providers (NBPs) 
        interconnected through exchange points: 
        NAPs (Network Access Points) and MAEs 
     (Metropolitan 
        Area Exchanges)
      
     Regional ISPs connects to the NBPs
      
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