SYN floods (was: does history repeat itself?)

Am I missing something....

If I am announcing a network via BGP I am more or less agreeing to carry
traffic for it. If I am not I am not. Therefore, if I filter based on my
outbound BGP announcements and do not allow any packets which have a source
address not originating from a network in my BGP announcements then I
should not be causing any harm to the networks which I am providing
connectivity to. This has the added benefit of stopping people from
defaulting into me at exchange points as I will not carry that traffic
across my backbone. I'd love to hear the holes in this theory.

Justin Newton
Internet Architect
Erol's Internet Services