Boeing Research & Technology Unaffiliated 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. Both IPv4 and IPv6 fragmentation have further been classified as fragile to the point that their use is discouraged. This specification addresses these limitations by defining an IPv6 Extended Fragment Header (EFH) that includes a 64-bit Identification in the context of more robust, secure and efficient fragmentation and reassembly procedures.