Bicone Source Address Validation

Source address validation (SAV) aims to avoid improper blocking of legitimate traffic while maintaining directionality. Existing SAV mechanisms commonly rely on ingress allowlist filters on interfaces facing customer or lateral peer Autonomous Systems (ASes), which can result in improper blocking when the allowlist is incomplete. This document analyzes this issue and describes an alternative ingress SAV approach based on a blocklist of prefixes exclusively associated with the provider cone. Network operators may select either approach based on their operational context.