destination node(s), plus the upper-layer header and data.

   The Fragmentable Part of the original packet is divided into
   fragments, each, except possibly the last ("rightmost") one, being an
   integer multiple of 8 octets long.  The fragments are transmitted in
   separate "fragment packets" as illustrated:

   original packet:

   +------------------+--------------+--------------+--//--+----------+
   |  Unfragmentable  |    first     |    second    |      |   last   |
   |       Part       |   fragment   |   fragment   | .... | fragment |
   +------------------+--------------+--------------+--//--+----------+









 
RFC 1883                   IPv6 Specification              December 1995


   fragment packets:

   +------------------+--------+--------------+
   |  Unfragmentable  |Fragment|    first     |
   |       Part       | Header |   fragment   |
   +------------------+--------+--------------+

   +------------------+--------+--------------+
   |  Unfragmentable  |Fragment|    second    |
   |       Part       | Header |   fragment   |
   +------------------+--------+--------------+
                         o
                         o
                         o
   +------------------+--------+----------+
   |  Unfragmentable  |Fragment|   last   |
   |       Part       | Header | fragment |
   +------------------+--------+----------+

   Each fragment packet is composed of:

      (1) The Unfragmentable Part of the original packet, with the
          Payload Length of the original IPv6 header changed to contain
          the length of this fragment packet only (excluding the length
          of the IPv6 header itself), and the Next Header field of the
          last header of the Unfragmentable Part changed to 44.

      (2) A Fragment header containing:

               The Next Header value that identifies the first header of
               the Fragmentable Part of the original packet.

               A Fragment Offset containing the offset of the fragment,
               in 8-octet units, relative to the start of the
               Fragmentable Part of the original packet.  The Fragment
               Offset of the first ("leftmost") fragment is 0.

               An M flag value of 0 if the fragment is the last
               ("rightmost") one, else an M flag value of 1.

               The Identification value generated for the original
               packet.

      (3) The fragment itself.

   The lengths of the fragments must be chosen such that the resulting
   fragment packets fit within the MTU of the path to the packets'
   destination(s).




 
RFC 1883                   IPv6 Specification              December 1995


   At the destination, fragment packets are reassembled into their
   original, unfragmented form, as illustrated:

   reassembled original packet:

   +------------------+----------------------//------------------------+
   |  Unfragmentable  |                 Fragmentable                   |
   |       Part       |                     Part                       |
   +------------------+----------------------//------------------------+

   The following rules govern reassembly:

      An original packet is reassembled only from fragment packets that
      have the same Source Address, Destination Address, and Fragment
      Identification.

      The Unfragmentable Part of the reassembled packet consists of all
      headers up to, but not including, the Fragment header of the first