Flowspec Indirection-id Redirect for SRv6

This document defines extensions to "FlowSpec Redirect to indirection-id Extended Community" for SRv6. This extended community can trigger advanced redirection capabilities to flowspec clients for SRv6. When activated, this flowspec extended community is used by a flowspec client to retrieve the corresponding next-hop and encoding information within a localised indirection-id mapping table. The functionality detailed in this document allows a network controller to decouple the BGP flowspec redirection instruction from the operation of the available paths.