Challenges in Inferring Internet Interdomain Congestion

We introduce and demonstrate the utility of a method to localize and quantify inter-domain congestion in the Internet. Our Time Sequence Latency Probes (TSLP) method depends on two facts: Internet traffic patterns are typically diurnal, and queues increase packet delay through a router during periods of adjacent link congestion. Repeated round trip delay measurements from a single test point to the two edges of a congested link will show sustained increased latency to the far (but not to the near) side of the link, a delay pattern that differs from the typical diurnal pattern of an uncongested link. We describe our technique and its surprising potential,carefully analyze the biggest challenge with the methodology (interdomain router-level topology inference), describe other less severe challenges, and present initial results that are sufficiently promising to motivate further attention to overcoming the challenges.