IPv6の仕様（IPv6ヘッダフォーマット）

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Version| Prio. |                   Flow Label                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Payload Length        |  Next Header  |   Hop Limit   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                         Source Address                        +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                      Destination Address                      +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Version              4-bit Internet Protocol version number = 6.

   Prio.                4-bit priority value.  See section 7.

   Flow Label           24-bit flow label.  See section 6.

   Payload Length       16-bit unsigned integer.  Length of payload,
                        i.e., the rest of the packet following the
                        IPv6 header, in octets.  If zero, indicates that
                        the payload length is carried in a Jumbo Payload
                        hop-by-hop option.

   Next Header          8-bit selector.  Identifies the type of header
                        immediately following the IPv6 header.  Uses
                        the same values as the IPv4 Protocol field
                        [RFC-1700 et seq.].

   Hop Limit            8-bit unsigned integer.  Decremented by 1 by
                        each node that forwards the packet. The packet
                        is discarded if Hop Limit is decremented to
                        zero.

   Source Address       128-bit address of the originator of the
                        packet.  See [RFC-1884].

   Destination Address  128-bit address of the intended recipient
                        of the packet (possibly not the ultimate
                        recipient, if a Routing header is present).
                        See [RFC-1884] and section 4.4.