1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +---------------+---------------+-------+-----+-+---------------+
  |     Kind      |  Length = 12  |Subtype|(rsv)|B|   Address ID  |
  +---------------+---------------+-------+-----+-+---------------+
  |                   Receiver's Token (32 bits)                  |
  +---------------------------------------------------------------+
  |                Sender's Random Number (32 bits)               |
  +---------------------------------------------------------------+