The redundant links to the customer site that traverse independent underlay carriers, and in some cases, equal-cost paths that we want to load-balance across, are the hard part. I’m not going to trust STP for that, and we aim for <3sec failover where we do have redundant paths. ERPS can handle the failover, but not the load-balancing. Any L2-over-L3 encapsulation protocol can handle the failover + ECMP features, but I need to do it at ~10G (~20G if ECMP) wire speed.