Effective placement of resources used to support distributed services in 
the Internet depends on an accurate representation of Internet topology 
and routing.  Representations of autonomous system (AS) level topology 
derived solely from BGP tables show only a subset of the connections that 
actually get used.  However, in many cases, missing connections can be 
discovered by simple traceroutes.  In addition, the differences between 
customer-to-provider links, peer-to-peer links, and sibling-to-sibling 
links are useful distinctions for the resource placement problem which is
the focus of our work.  Using two complementary mechanisms, we improve the
accuracy of an AS forest as a predictor of packet paths.  One mechanism
uses recent insights that packets flow unidirectionally across 
customer-provider inter-AS links.  Annotations are added to the AS forest
to indicate links that appear to be peering versus those that appear to be 
customer-provider links.  The other mechanism provides links between trees 
by remembering the most recently seen similar traceroute.  Through the
application of these mechanisms we are able to accurately predict over 90%
of the paths taken by traceroutes through AS space.