The Free On-line Dictionary of Computing (30 December 2018):

Internet Protocol
IP

    (IP) The network layer for the TCP/IP
   protocol suite widely used on Ethernet networks, defined
   in STD 5, RFC 791.  IP is a connectionless,
   best-effort packet switching protocol.  It provides
   packet routing, fragmentation and re-assembly through
   the data link layer.

   IPv4 is the version in widespread use and IPv6 was just
   beginning to come into use in 2000 but is still not widespread
   by 2008.

   [Other versions?  Dates?]

   (2000-12-19)