Filtering only serves to violate the premise of BGP4 and routing in general -
that the metrics and route weights will guide a packet to the most expeditious
path. When you remove some of those choices, you second-guess the physical
realities of the time.
Filtering does not violate any premise in BGP4. BGP4 was
designed to allow the assignment of administrative weights.
That is to say, POLICY. And I happen to believe not accepting a
route for 204.68.252/24 from someone who is not authorized to
route the associated ASes is a good policy. If someone
announced a route to NET99 that was not authorized then ANS
would ignore that route, and you would still have connectivity
through us. Only the customers of the ISP who misconfigured his
equipment, and anyone uniformed enough to accept routes from
him, would lose out.
Yes, as Vadim points out, there is an administrative cost to
Yes, you need bigger, faster routers with a LOT more memory.
Yes, I see outages every day because someone did not file a NACR,
filed it incorrectly, or it was not processed on time.
But the resulting connectivity is, IMHO, more robust than, to
borrow a metaphor, having promiscuous sessions with all your
peers and praying you don't get the 'black hole',
ANS Network Operations