The global Internet has emerged to become an integral part of everyday life. Internet is now as fundamental a part of the infrastructure as is the telephone system or the road network. Peer-to-Peer (P2P) is the logical antithesis of the Client-Server (CS) paradigm that has been the ostensible predominant paradigm for IP-based networks since their inception. Current research indicates that P2P applications are responsible for a substantial part of the Internet traffic. New P2P services are developed and released at a high pace. The number of users embracing new P2P technology is also increasing fast. It is therefore important to understand the impact of the new P2P services on the existing Internet infrastructure and on legacy applications. This report describes a measurement infrastructure geared towards P2P network traffic collection and analysis, and presents measurement results for two P2P applications: Gnutella and BitTorrent.