Performance limitations of ADSL users : a case study

We report results from the analysis of a 24-hour packet trace containing TCP traffic of approximately 1300 residential ADSL clients. Some of our observations confirm earlier studies: 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 a 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 (P2P) applications clients use, which limit the transmission rate and not due to network congestion, for instance. P2P applications typically impose upload rate limits to avoid uplink saturation that hurt download performance. Our analysis shows that these rate limits are very low and, as a consequence, the aggregate download rates for these applications are low.