[pumplekin]

BFD or Ethernet-OAM is the standard here.

It can get a bit hardware dependant but getting <50ms failovers from software based BFD in BIRD or FRR is fairly easy, and I've tested down to < 1ms before with hardware based BFD echo. ~50ms is the point at which a user making a traditional VOIP call won't notice the path switch.

You can get NIC's for computers (like most Nvidia/Meallanox or higher end Broadcom/Intel NIC's that do hardware BFD, and its obviously included in higher end networking kit.

You then link the BGP routes to the health of the BFD session for which that path is the next hop, and you get super quick withdrawls.