On the interaction between Internet applications and TCP

We focus in this paper on passive traffic measurement techniques that collect traces of TCP packets and analyze them to derive, for example, round-trip times or aggregate metrics such as average throughput. The seminal work of Zhang [1] has shown that for more than 50% of the TCP connections observed, it is not the network bandwidth that limits the throughput but rather the application or mechanisms such as TCP slow start or too small a receiver window. Certain types of analysis of the network characteristics are meaningful only when performed on TCP traffic that experiences minimal interference by the application. To eliminate such interference, we propose a generic method that partitions the packets of a TCP connection in bulk data transfer and in application limited periods: The packets of a bulk data transfer period (BTP) experience minimal interference from the application, while the packets of an application limited period (ALP) experience interference from the application that prevents TCP from fully utilizing the network resources because the application does not produce data fast enough. As a proof of concept, we apply our algorithm to public Internet traffic traces and show that unless the effects of the application are filtered out, studying the end-to-end path and traffic characteristics from a network point of view can produce biased results.