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 = 16  |Subtype|(rsv)|B|   Address ID  |
  +---------------+---------------+-------+-----+-+---------------+
  |                                                               |
  |                Sender's Truncated HMAC (64 bits)              |
  |                                                               |
  +---------------------------------------------------------------+
  |                Sender's Random Number (32 bits)               |
  +---------------------------------------------------------------+