Boeing Research & Technology SiPanda The Internet Protocol, version 4 (IPv4) header includes a 16-bit Identification field in all packets, but this length is too small to ensure reassembly integrity even at moderate data rates in modern networks. Even for Internet Protocol, version 6 (IPv6), the 32-bit Identification field included when a Fragment Header is present may be smaller than desired for some applications. This specification addresses these limitations by defining an IPv6 Extended Fragment Header (EFH) that includes a 64-bit Identification with efficient fragmentation and reassembly procedures.