IPv4

Internet Protocol version 4 (IPv4) is the fourth version of the Internet Protocol (IP). It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. IPv4 was the first version deployed for production on SATNET in 1982 and on the ARPANET in January 1983. It is still used to route most Internet traffic today,[1] despite the ongoing deployment of a successor protocol, IPv6.

Internet Protocol version 4
Protocol stack
IPv4 packet
Purposeinternetworking protocol
Developer(s)DARPA
Introduced1981
OSI layerNetwork layer
RFC(s)RFC 791

IPv4 uses a 32-bit address space which provides 4,294,967,296 (232) unique addresses, but large blocks are reserved for special networking methods.