Heuristic-Based Real-Time P2P Traffic Identification Peer-to-Peer (P2P) networks have seen a rapid growth, spanning diverse applications like online anonymity (Tor), online payment (Bit coin), file sharing (Bit Torrent), etc. However, the success of these applications has raised concerns among ISPs and Network administrators. These types of traffic worsen the congestion of the network, and create security vulnerabilities. Hence, P2P traffic identification has been researched actively in recent times. Early P2P traffic identification approaches were based on port-based inspection. Presently, Deep Packet Inspection (DPI) is a prominent technique used to identify P2P traffic. But it relies on payload signatures which are not resilient against port masquerading, traffic encryption and NATing. In this paper, we propose a novel P2P traffic identification mechanism based on the host behaviour from the transport layer headers. A set of heuristics was identified by analysing the off-line datasets collected in our test bed. This approach is privacy preserving as it does not examine the payload content. The usefulness of these heuristics is shown on real-time traffic traces received from our campus backbone, where in the best case only 0.20% of flows were unknown.