List of IP protocol numbers

This is a list of the IP protocol numbers found in the 8-bit Protocol field of the IPv4 header and the 8-bit Next Header field of the IPv6 header. It is an identifier for the encapsulated protocol and determines the layout of the data that immediately follows the header. Because both fields are eight bits wide, the possible values are limited to the 256 values from 0 to 255, of which just over half had been allocated
Protocol numbers are maintained and published by the Internet Assigned Numbers Authority.