3. Service Route Automated Steering on Color-Aware Paths

An ingress PE (or ASBR) E1 automatically steers traffic for a C-colored service route V/v from E2 onto a (E2, C) color-aware path. If multiple such paths exist, a preference scheme is used to select the best path. The default preference scheme is IGP Flexible Algorithm first, then SR Policy, then BGP CAR.

An egress PE can express its intent that traffic should be steered in a specific manner through the transport layer by including a BGP Color-EC in the associated service route. The ingress PE uses the service route's next hop and BGP Color-EC to steer service traffic on the CAR (E, C) route.

This is consistent with automated service route steering on SR Policy (a routing solution providing color-aware paths) as defined in [RFC9256]. All steering variants described in [RFC9256] apply to BGP CAR paths: on-demand steering, per-destination steering, per-flow steering, and color-only steering.

Service steering via BGP CAR routes applies to any BGP SAFI, including SAFIs for IPv4/IPv6 (SAFI 1), L3VPN (SAFI 128), Pseudowire (PW), EVPN (SAFI 70), FlowSpec, and BGP-LU (SAFI 4).

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