RFC 9871: BGP Color-Aware Routing (CAR)

This document describes a BGP-based routing solution to establish end-to-end intent-aware paths across a multi-domain transport network. The transport network can span multiple service provider and customer network domains. The BGP intent-aware paths can be used to steer traffic flows for service routes that need a specific intent. This solution is called BGP Color-Aware Routing (BGP CAR). This document describes the routing framework and BGP extensions to enable intent-aware routing using the BGP CAR solution. The solution defines two new BGP SAFIs (BGP CAR SAFI and BGP VPN CAR SAFI) for IPv4 and IPv6. It also defines an extensible Network Layer Reachability Information (NLRI) model for both SAFIs that allows multiple NLRI types to be defined for different use cases. Each type of NLRI contains key and TLV-based non-key fields for efficient encoding of different per-prefix information. This specification defines two NLRI types: Color-Aware Route NLRI and IP Prefix NLRI. It defines non-key TLV types for the MPLS label stack, SR-MPLS label index, and Segment Routing over IPv6 (SRv6) Segment Identifiers (SIDs). This solution also defines a new Local Color Mapping (LCM) Extended Community.