Difference of syn-64 and syn-66

Syn-64:
TCP Header (20 bytes) + IP header (20 bytes) + 6 bytes pad = 46 bytes, because the minimum IP address is 46 bytes, so fill 6 bytes
With the 18-byte (6 + 6 + 2 + 4) Ethernet encapsulation, the total size is 64 bytes.
However, the option field in the TCP header is not normal. Therefore, the SYN packet is also called malformed. Some firewalls directly drop the SYN packet. In synflood attacks, this is also a type, but more common is syn-66.

Syn-66:
TCP Header (20 bytes) + IP header (20 bytes) + tcpoption (8 bytes) = 48 bytes
In addition, the 18-byte (6 + 6 + 2 + 4) Ethernet encapsulation makes the total size 66 bytes.