Header The IPv4 packet header consists of 14 fields, of which 13 are required. The 14th field is optional and aptly named: options. The fields in the header are packed with the most significant byte first (network byte order), and for the diagram and discussion, the most significant bits are considered to come first (MSB 0 bit numbering). The most significant bit is numbered 0, so the version field is actually found in the four most significant bits of the first byte, for example.
header the ipv4 packet header consists of 14 fields of which 13 are required the 14th field is optional and aptly named options the fields in the header are packed with the most significant byte first (network byte order) and for the diagram and discussion the most significant bits are considered to come first (msb 0 bit numbering) the most significant bit is numbered 0 so the version field is actually found in the four most significant bits of the first byte for example