A quick clarification -- the liberal BGP widthraw policy implemented by Cisco (and a few other vendors) only accounts for a small fraction of the ~5 million plus daily withdraws in the default-free Internet. The real source of all these spurious withdraws remains a bit of a mystery. Our data shows some strange sort of 30 second looping/oscilation behavior is taking place. Possible causes of this behavior include configuration errors, unexpected IGP-EGP interactions, vendor implementation bugs, and problems inherent with the BGP protocol itself.
The source of the millions of BGP withdraws is NOT Cisco's "liberal BGP withdraw" policy -- this generates a fairly minor number of extra withdraws (O(n) per router), and there are a quite a few valid and compelling reasons for wanting implementing BGP this way.
- Craig
What %age of the route assertions and withdrawls are substantially the same set of routes each day? Avi