Virtual Path Identifier
Virtual Path Identifier refers to an 8-bit (user to network packets) or 12-bit (network-network packets) field within the header of an Asynchronous Transfer Mode packet. The VPI, together with the VCI (Virtual Channel Identifier) is used to identify the next destination of a cell as it passes through a series of ATM switches on its way to its destination. VPI is useful to reduce the switching table for some Virtual Circuits which have common path.