0                   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
+---------------+-----------------------------------------------+
| Type: 21      |  Length: 12   |1|0|0|     Reserved    |Delay:1|
+---------------+-------------------------------+---------------+
|       Seq number: 123         |      7        |       e       |
+---------------+-----------------------------------------------+
|      x        |       a       |      m        |       p       |
+---------------------------------------------------------------+
|      l        |       e       |      3        |       o       |
+---------------------------------------------------------------+
|      r        |       g       |      0        |   0 (padding) |
+---------------------------------------------------------------+
|   0 (padding) |  0 (padding)  |   0 (padding) |   0 (padding) |
+---------------+---------------+---------------+---------------+
|  RDNSS option (RFC 8106) length: 5                          ...
...                                                           ...
...                                                             |
+---------------------------------------------------------------+
| Prefix Information Option (RFC 4861) length: 4              ...
...                                                             |
...                                                             |
+---------------------------------------------------------------+