The Firewall Services Module (FWSM) - a high-speed, integrated firewall module that provides the fastest firewall data rates in the industry: 5 GB throughput, 100, 000 CPS, and 1M concurrent connections. Up to four FWSMs can be installed in a single chassis providing scalability to 20 GB per chassis. As part of the world-leading Cisco PIX Firewall family, the FWSM provides large enterprises and service providers with unmatched security, reliability, and performance.The FWSM leverages Cisco PIX technology and runs the Cisco PIX Operating System (OS), a real-time, hardened, embedded system that eliminates security holes and performance-degrading overhead. At the heart of the system, a protection scheme based on the Adaptive Security Algorithm (ASA) offers stateful connection-oriented firewalling. Using ASA, the FWSM creates a connection table entry for a session flow based on the source and destination addresses, randomized TCP sequence numbers, port numbers, and additional TCP flags. The FWSM controls all inbound and outbound traffic by applying the security policy to these connection table entries.