Application-Level Performance of ADSL Users

We report results from the analysis of a 24-hour packet trace containing aggregate TCP traffic of approximately 1300 residential ADSL clients. We make observations similar to earlier studies by the research community: the major fraction of the total traffic originates from P2P applications and small fractions of connections and clients are responsible for the vast majority of the traffic. However, our main contribution is throughput performance analysis of the clients. We observe suprisingly low utilizations of upload and download capacity for most of the clients. Furthermore, by using our TCP root cause analysis tool, we obtain a striking result: in over 90% of the cases, the low utilization is mostly due to the applications that clients use and that limit the transmission rate and not network congestion, for instance. P2P applications typically impose upload rate limits to avoid uplink saturation that would damage download performance. Our analysis shows evidence that these rate limits, set either by the user or by the application, are too conservative and, as a consequence, the overall performance of these applications is poor. Deployment of more intelligent rate limit mechanisms in such a scenario would imply increase in clients’ throughput at the expense of an increased load in backbone networks.