caches for peer-to-peer trafic

Hey guys, I wanted to ask that if ISPs use any kind of caching system for peer-to-peer traffic? It seems to be difficult thing to do, though there is some research going on (including me). However, I wanted to ask about the practices being used by ISPs and I suppose this is the best audience to ask such a question. Thanks and regards, Ghulam Murtaza PhD Student, Lahore University of Management Sciences