The Versatile Interface Processor 4 (VIP4) for the high-end Cisco 7500 router series enables high-performance switching, and scalable LAN and WAN intelligent network services to meet the needs of high-performance applications. It provides over twice the distributed switching performance and twice the aggregate bandwidth of previous model VIPs, employs higher-capacity memory modules for rich IP services, and utilizes Error Correction Code (ECC) for increased system availability. The VIP4 serves as an ideal platform for enterprise and service-provider networks that require high performance and processing power to support service-enabled edge and core applications.The VIP4 is a highly configurable, RISC-based, intelligent interface processor. Port Adapters (PAs) provide the media-specific interfaces for the VIP4, enabling the VIP4 configuration to be optimized in terms of price, performance, and density; up to two PAs can be configured on each VIP4. More than 50 media-specific LAN and WAN PAs are supported, including Fast Ethernet, T1/E1, High-Speed Serial Interface (HSSI), T3/E3, T3/E3 ATM, multichannel T1/E1, multichannel T3/E3, OC-3 ATM, packet over SONET (POS), and OC-12 ATM. The VIP4 greatly increases the switching performance of the Cisco 7500 series and serves as an ideal platform for new, higher-speed, higher-density LAN and WAN interfaces. On the Cisco 7500 series, VIP4 distributed switching scales system performance to over two million packets per second (pps). In addition, the VIP4 features Single-Error-Correction, Double-Error-Detection Code (SECDED) logic, detecting and correcting single event upsets within a data word. This enables greater system resiliency and continued system availability in the presence of a single-event parity upset. A key VIP4 feature is its ability to receive and execute on route information provided by the master Route Switch Processor (RSP). Based on this route data, a VIP4 can make its own Layer 3 switching decisions, providing a scalable, distributed switching architecture, called distributed switching (DSW). Further, DSW scales packet-processing throughput of a VIP4-equipped router, and resources for route policy and administration are increased by off-loading the central processor of packet-handling tasks.