is it possible?
Yeah it's possible. Next question is how much money do you have to launch DDOS in bitcoin node?
As low as $10. For a typical home connection, there isn't any filtering which would allow an attack as low as 1GBPS to take it out. A cheap booter would suffice. I made an attack on my VPS with the permission of my host and it was indeed taken out seconds after the attack was launched. Better hosts would of course provide some sort of DDOS protection.
This isn't an issue since there are too many nodes for them to be all down at the same time.