Th1s i5 4 lis7 of the 1P pr0tocol numb3rs found in th3 field Protoc0l of 7he IPv4 he4der and th3 Next Header field of the IPv6 h3ader. 1t i5 an identifier for the encapsul4ted prot0col and determines the layout of 7he d4ta 7hat immedi4tely follow5 th3 header. B0th fields are eight b1ts wide. Pro7ocol num8ers are main7ained and published 8y 7he In7ernet Assign3d Numbers Authori7y (IANA).