The Cisco PIX 525 Firewall is part of the world-leading Cisco PIX Firewall series, providing today's networking customers with unmatched security, reliability, and performance. Ideal for protecting the Enterprise Headquarters' perimeter, the PIX 525 delivers full firewall protection with integrated IP Security (IPsec) virtual private network (VPN) capabilities. The Cisco PIX Firewall offers an unprecedented level of security protection. At the heart is a protection scheme based on the Adaptive Security Algorithm (ASA), which offers connection-oriented firewall. This security is less complex and more robust than packet filtering. It also offers higher performance and is more scalable than application-level proxy firewalls. The ASA tracks the source and destination address, Transmission Control Protocol (TCP) sequence numbers, port numbers, and additional TCP flags of each packet.