Sticky Decision Function (SDF) is a feature that ensures that VPN traffic is handled by the same core on a Security Gateway with multiple CPU cores. This improves the performance and stability of VPN tunnels by avoiding out-of-order packets and reducing encryption overhead. However, the limitation of employing SDF is that acceleration technologies, such as SecureXL and CoreXL are disabled when activating SDF. This means that SDF may reduce the overall throughput and scalability of the Security Gateway. Therefore, SDF should be used only when necessary and only on gateways that are dedicated to VPN traffic. Reference:R81 Performance Tuning Administration Guide