Just a curious thought about AS_PATH. The way loop prevention works in BGP is that if I see my own AS in the AS_PATH attribute, then I discard the route.
My curiosity is this ... why did my neighbor send me the route in the first place? He knows my AS number. He could see the route had my AS in the AS_PATH attribute. So why did he bother to send it to me, if he knew I would just discard it?