Is the export policy selective under valley-free?

Randy Bush randy at
Wed Sep 3 04:40:32 CDT 2008

> I think that yes, the valley-free property is a necessary but not 
> sufficient criteria for generating the set of in-reality-valid paths
> on the Internet.

i assure you that the actual topology is not valley free.  e.g. there
are many backup or political hack transit paths [0] between otherwise
peers and there are also backup customer/provider reversals.  often
academic researchers assume the valley free condition to simplify their
models.  often this creates serious amusing in their results.

randy, on holiday and should not be reading nanog, let alone responding

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