Abstract: The fact that BitTorrent networks generate a large portion of the Internet traffic has attracted many experts to focus on it．Unfortunately,due to the existing tools’ inability to measure dynamic volume of traffic between two individual peers,there’s few research on the traffic flow between the peers in real BT networks．The authors designed an inter-peer traffic data collection system,got the real data after implementing it on the Planetlab platform and verified the data’s correctness,analyzed the measured data and found that (1) the return of list of neighbor peers from Tracker server to a downloading peer will be affected by the peers’ joining time into the network,(2) for 50% or more peers,the downloaded data from the seed is zero,and for most peers,the downloading seldom depends on seed,which demonstrates the advantage of the P2P mechanism．

Key words: BitTorrent networks,Traffic flow between peers,Tracker algorithm,Neighbor peers,Seed