Something like http://www.sandvine.com/products/ppe8200.asp would do that--primarily preference other hosts on the WAN.

Quote:

The Sandvine PPE 8200 is designed to lower network costs resulting from P2P traffic by logically rearranging the peer-to-peer network topology. Sandvine's patent-pending technology analyzes all P2P searches and ensures that each is routed down the least-cost network path

I haven't heard anything back, but I wondered if another gnutella client (like BearShare) is affected the same way.