Comment by mindslight

I've had the exact same thing happen when a host crashed. Relatively modern Intel network chip on the host, Netgear GS108 switch (BCM5398 I believe). Presumably when the host stops servicing interrupts, the card's buffer fills up and then generates pause frames.

I don't think it requires the switch to have a bad buffer policy - all the switch ports didn't die at once, just one-by-one as each connected device tried to send a broadcast packet. I don't see a way of avoiding this logical situation if pause frames are sacrosanct - it seems that a switch would need a heuristic to forget pausing and start silently dropping packets to only the affected ports.

(I've since disabled pause frames on those cards, since I don't really need them.)