Soutenance de thèse R. Ravaioli: "Active inference of network neutrality"
In the last decade, some ISPs have been reported to discriminate against specific user traffic, especially if generated by bandwidth-hungry applications (e.g., peer-to-peer, video streaming) or competing services (e.g. Voice-over-IP).
Network neutrality, a design principle according to which a network should treat all incoming packets equally, has been widely debated ever since. In this thesis we present ChkDiff, a novel tool for the detection of traffic differentiation at the Internet access. In contrast to existing work, our method is agnostic to both the applications being tested and the shaping mechanisms deployed by an ISP. The experiment comprises two parts, in which we check for differentiation separately on upstream and downstream traffic that we previously dump directly from the user. In the upstream direction, ChkDiff replays the user's outgoing traffic with a modified TTL value in order to check for differentiation on routers at the first few hops from the user. By comparing the resulting delays and losses of flows that traversed the same routers, and analyzing the behaviour on the immediate router topology spawning from the user end point, we manage to detect instances of traffic shaping and attempt to localize shapers. Our study on the responsiveness of routers to TTL-limited probes consolidates our choice of measurements in the upstream experiment. In the downstream experiment, we replay the user's incoming traffic from a measurement server and analyze per-flow one-way delays and losses, while taking into account the possibility of multiple paths between the two endpoints. Along the chapters of this thesis, we provide a detailed description of our methodology and a validation of our tool.