Minimally-Intrusive Frequent Round Trip Time Measurements Using Synthetic Packet-Pairs – Extended Report∗

Abstract—Accurate and frequent round trip time (RTT) measurements are important in both testbeds and opera-tional networks. Active measurement techniques, such as “ping”, inject probe packets that can modify the behaviour of the observed network and may produce misleading RTT estimates if the network handles probe packets differ-ently to regular packets. Previous passive measurement techniques address these issues, but require precise time synchronisation or are limited to certain traffic types, such as TCP flows. We introduce a passive technique for RTT measurement called Synthetic Packet-Pairs (SPP). SPP provides frequently updated RTT measurements using any network traffic already present in the network without the need for time synchronisation. SPP accurately measures the RTT experienced by any application’s traffic, even applications that do not exhibit symmetric client-server packet exchanges. We experimentally demonstrate the advantages of SPP in different scenarios. Index Terms—Passive measurement, Round Trip Time, RTT