0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   TIMESTAMP                   |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                      TTL                      |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                     POW_0                     |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                       ...                     |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                    POW_(Z-1)                  |
+-----------------------------------------------+
|       ZONE TYPE       |    ZONE KEY           /
+-----+-----+-----+-----+                       /
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
/                   SIGNATURE                   /
/                                               /
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+