|-- SCHC ACK Header --|- W=w1 -|...|---- W=wi -----|
+------+------+-------+--------+...+------+--------+------+-------+
|RuleID|W=b'w1| C=b'0 | Bitmap |...|W=b'wi| Bitmap | 000  |b'0-pad|
+------+------+-------+--------+...+------+--------+------+-------+
|8 bits|3 bits| 1 bit | 31 bits|...|3 bits| 31 bits|3 bits|