The method of SYN flood protection employed starting with SonicOS uses stateless SYN Cookies, which increase reliability of SYN Flood detection, and also improves overall resource utilization on the SonicWall. With stateless SYN Cookies, the SonicWall does not have to maintain state on half-opened connections. Instead, it uses a cryptographic calculation (rather than randomness) to arrive at SEQr (see Understanding a TCP Handshake).