The Cisco Secure PIX Firewall 535 delivers carrier-class performance that meets the needs of large enterprise networks as well as service providers. As part of the world-leading Cisco Secure PIX Firewall series, it provides today's networking customers with unmatched security, reliability, and performance. The PIX 535 integrates stateful firewall and IP Security (IPsec) virtual private network (VPN) functionality with Gigabit Ethernet throughput.The PIX 535 is a purpose-built firewall appliance that offers an unprecedented level of protection. This is tightly integrated with the PIX Operating System (OS), which is a proprietary, hardened system that eliminates security holes and performance degrading overhead. At the heart of this system is a protection scheme based on the Adaptive Security Algorithm (ASA), which offers stateful connection-oriented firewalling that is capable of 500, 000 concurrent connections while at the same time blocking common denial of service (Dos) attacks.The Cisco PIX 535 Firewall, with a restricted software license, includes 512 MB of RAM and support for up to six Gigabit Ethernet or 10/100 Fast Ethernet interfaces, as well as a single VAC.