The Internet Protocol (IP) is the principal communications protocol used for relaying datagrams (also known as network packets) across an internetwork using the Internet Protocol Suite responsible for routing packets across network boundaries. It is the primary protocol that establishes the Internet.
IP is the primary protocol in the Internet Layer of the Internet Protocol Suite and has the task of delivering datagrams from the source host to the destination host solely based on the addresses. For this purpose, IP defines datagram structures that encapsulate the data to be delivered. It also defines addressing methods that are used to label the datagram source and destination.
Historically, IP was the connectionless datagram service in the original Transmission Control Program introduced by Vint Cerf and Bob Kahn in 1974, the other being the connection-oriented Transmission Control Protocol (TCP). The Internet Protocol Suite is therefore often referred to as TCP/IP.
The first major version of IP, Internet Protocol Version 4 (IPv4), is the dominant protocol of the internet. Its successor is Internet Protocol Version 6 (IPv6), which is increasing in use.