Scalable, Loop-Free BGP FRR using Repair Label
Consider a BGP free core scenario. Suppose the provider edge BGP speaker PE1, PE2,..., PEn know about a prefix P/p via the external routers CE1, CE2,..., CEm. If the PE router PEi loses connectivity to the primary path, whether it is another PE router or a CE router, it desirable to immediately restore traffic by rerouting packets arriving to PEi and destined to the prefix P/p to one of the other PE routers that advertised P/p, say PEj, until BGP re-converges. However if the loss of connectivity of PEi to the primary path also resulted in the loss of connectivity between PEj and CEj, rerouting a packet without before the control plane converges may result in a loop. In this document, we propose using a repair label for traffic restoration while avoiding loops. We propose advertising the ''repair'' label through BGP.