TosolvethescalingproblemwithEthernet,andtoallowsupportforothertypesofLANsandpoint-to-point links as well, the Internet Protocol was developed. Perhaps the central issue in the design of IP was to support universal connectivity (everyone can connect to everyone else) in such a way as to allow scaling to enormous size (in 2013 there appear to be around ~109 nodes, although IP should work to 1010 nodes or more), without resulting in unmanageably large forwarding tables (currently the largest tables have about 300,000 entries.) In the early days, IP networks were considered to be “internetworks” of basic networks (LANs); nowadays users generally ignore LANs and think of the Internet as one large (virtual) network. To support universal connectivity, IP provides a global mechanism for addressing and routing, so that packets can actually be delivered from any host to any other host. IP addresses (for the most-common
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