HPAP: High precision active probe for path round-trip delay measurement

Path round-trip delay, i.e., path round-trip time (RTT), is one of the key metrics for evaluating network performance, also plays a crucial role in several overlay network construction protocols, peer-to-peer (P2P) applications, etc. In this paper, we present HPAP, a high precision active probe for path RTT measurement, which is based on Berkeley Packet Filter (BPF) technology. When the measuring probe packets arrive at or depart from the Network Interface Card (NIC), the BPF can capture them quickly, and can mark the timestamps immediately. The HPAP can calculate the path RTT value according to these timestamps. By this method, the time-stamp position can be removed from application program to data link layer of TCP/IP stack. The experimental results show that the new scheme can nearly eliminate the location error, and can practically improve the path RTT measuring accuracy. This scheme has low-cost in the investment, so it can be applied widely.