Measurement-based studies indicate that there is a severe tension between P2P applications and ISPs. In this paper, we propose a novel HTTP-based Peer-to-Peer (HPTP) framework to relieve this tension. The key idea is to exploit the widely deployed web cache proxies of ISPs to trick them into caching P2P traffic. This is achieved via a process we refer to as HTTPifying: we segment (if necessary) large P2P files or streams into smaller chunks, encapsulate and transport them using the HTTP protocol so that they are cacheable. We outline the design of several key tools of the proposed HPTP framework, cache detection and usability test tools, and describe a cache-aware tree construction (CATC) protocol for delivering P2P streaming traffic as an example to showcase the HPTP framework. Simulation results demonstrate that HPTP can lead to significant performance improvements. We argue that the HPTP framework will benefit both ISPs and end users (P2P as well as normal web users) by significantly reducing network overload caused by repetitive P2P traffic.