Internet Governance Glossary
2
2.21 IPv4 / Internet Protocol version 4
Connectionless internetworking protocol version 4 in the Internet’s Internet Layer supporting 32-bit IP addresses which allows for approximately 4 billion unique IP addresses.
Note:
IPv4 as used on packet-switched networks operating on a best effort delivery model is still dominantly in use today, the number 4 is the protocol version number carried in every IP datagram.