|-- Receiver-Abort Header -|
+-----------------------------------+-----------------+---------+
| RuleID | W=b'111 | C=b'1 | b'1111 |  0xFF (all 1's) | b'0-pad |
+--------+---------+-------+--------+-----------------+---------+
| 8 bits |  3 bits | 1 bit | 4 bit  |  8 bit          | 40 bits |
            next L2 Word boundary ->| <-- L2 Word --> |