Tsinghua Univ. Tsinghua Univ. UC3M Cisco Source Address Validation Improvement (SAVI) methods were developed to prevent nodes attached to the same IP link from spoofing each other's IP addresses, so as to complement ingress filtering with finer-grained, standardized IP source address validation. This document is a framework document that describes and motivates the design of the SAVI methods. Particular SAVI methods are described in other documents.