Comparison between IPv4 options and IPv6 extension headers: Comparison 1 . The header length field is eliminated in IPv6 because the length of the header is fixed in this version. 2.The service type field is eliminated in IPv6. The priority and flow label fields together take over the function of the service type field. 3.The total length field is eliminated in IPv6 and replaced by the payload length field. 4.The identification, flag, and offset fields are eliminated from the base header in IPv6. They are included in the fragmentation extension header. 5.The TTL field is called hop limit in IPv6. 6.The protocol field is replaced by the next header field. 7.The header checksum is eliminated because the checksum is provided by upper-layer protocols; it is therefore not needed at this level. 8.The option fields in IPv4 are implemented as extension headers in IPv6.