[eqvinox]

BGP Keepalives are not request-reply, they are simple scheduled transmissions. Which means even if one side is not reading, it may still be sending keepalives. So the other side keeps the session open, despite its own keepalives sitting in its send queue.

Also, any valid BGP message resets the keepalive timer, so the reading side just needs to occasionally pop something off the full queue and process it. Which, say, if you're swapping to hell and back, can still get done. (Assuming it even has the scheduling get to killing things due to holdtime expiry. It might just not be expiring anything anymore for reasons of floating face-down in the river.)