Detecting Traffic Differentiation in Backbone ISPs with NetPolice

Traffic differentiations are known to be found at the edge of the Internet in broadband ISPs and wireless carriers [13, 2]. The ability to detect traffic differentiations is essential for customers to develop effective strategies for improving their application perfor-mance. We build a system, called NetPolice, that enables detection of content- and routing-based differentiations in backbone ISPs. NetPolice is easy to deploy since it only relies on loss measurement launched from end hosts. The key challenges in building NetPo-lice include selecting an appropriate set of probing destinations and ensuring the robustness of detection results to measurement noise. We use NetPolice to study 18 large ISPs spanning 3 major conti-nents over 10 weeks in 2008. Our work provides concrete evidence of traffic differentiations based on application types and neighbor ASes. We identify 4 ISPs that exhibit large degree of differentiation on 4 applications and 10 ISPs that perform previous-AS hop based differentiation, resulting in up to 5 % actual loss rate differences. The significance of differences increases with network load. Some ISPs simply differentiate traffic based on port numbers irrespec-tive of packet payload and the differentiation policies may only be partially deployed within their networks. We also find strong corre-lation between performance differences and Type-of-Service value differences in the traffic