The Internet protocol suite is a collection of protocols that provide a networking model for the software systems of the Internet. The Internet protocol suite consists of four abstraction layers, and the Internet layer is an intermediate layer; above it is the transport layer, and below it is the link layer. The primary responsibility of the Internet layer is providing a 'framework' where data packets can be routed across IP networks. The following protocols are part of the Internet layer; although some are experimental protocols.
The Internet layer is dominated by the Internet Protocol (IP). The Internet Protocol (IP) is a core protocol of the Internet, and perhaps the most essential of any protocol. The Internet Protocol (IP) was designed in the 1970's as part of TCP/IP. As more and more protocols were developed for the Internet, TCP/IP was renamed as the Internet protocol suite. The Internet Protocol (IP) has remained an essential protocol of IP networks and the Internet since it's implementation onto computer networks - like ARPANET - in the 1980's.
The Internet Protocol (IP) provides a framework for assigning Internet hosts with an address (number), and defines the structure of data packets that enables the packet to be routed between IP networks. The Internet layer includes two versions of the Internet Protocol (IP): IPv4 (version 4) and IPv6 (version 6). IPv4 defines a 32 bit number - which is assigned to Internet hosts - IPv6 defines a 128 bit number, and was required because IPv4 ran out of numbers, due to the number of host computers connecting to the Internet.
The other protocols of the Internet layer tend to be an extension
of the Internet Protocol (IP): providing congestion notifications
and error handling for IPv4 and IPv6. The Internet layer, and specifically
the Internet Protocol (IP), form the bedrock of the Internet: they
enable IP networks to interconnect, and provide the potential for
them to communicate. The other layers of the Internet protocol suite
help transport and route IP data, or, create the data to be communicated.