The VPN Accelerator Card (VAC) for the Cisco Secure PIX Firewall series provides high-performance, tunneling and encryption services suitable for site-to-site and remote access applications. This hardware-based VPN accelerator is optimized to handle the repetitive but voluminous mathematical functions required for IPsec. Offloading encryption functions to the card not only improves IPsec encryption processing, but also maintains high-end firewall performance. As an integral component of the Cisco virtual private network (VPN) solution, the VPN Accelerator Card provides platform scalability and security while working seamlessly with services necessary for successful VPN deployments - encryption, tunneling, and firewall.The VPN Accelerator Card, which fits in a PCI slot inside the PIX chassis, encrypts data using the 56-bit Data Encryption Standard (DES) or 168-bit 3DES algorithms at speeds up to 100 Mbps. A PIX equipped with a VAC supports as many as 2, 000 encrypted tunnels for concurrent sessions with mobile users or other sites. In addition to encryption, the card handles a variety of other IPsec-related tasks - hashing, key exchange, and storage of security associations - which free the PIX main processor and memory to perform other perimeter security functions.