Cisco Systems Cisco Systems Cisco Systems Cisco Systems Unaffiliated Juniper Networks Segment Routing (SR) architecture allows a node to steer a packet flow through any topological path and service chain by leveraging source routing. The ingress node prepends a SR header to a packet containing a set of "segments". Each segment represents a topological or a service-based instruction. Per-flow state is maintained only at the ingress node of the SR domain. This document describes the BGP extension for announcing BGP Prefix Segment Identifier (BGP Prefix SID) information.