So first off, do ethernet sends ack frames or not?
if it doesn't : then how does a router know whether its neighbors are down or not?
if it does : then is it cumulative ack with an ack timer or one ack per received frame?
I'm asking this because in Link state algorithm i read somewhere that the blackhole problem is solved by the router because it will eventually realize that its neighbor is down, but how can it know if there is no ack frames?