How do Internet routing policies give rise to triangle inequality violations in latency measurements?

摘要

Round-Trip-Times (RTTs) play an important role in Internet latency measurements. In this paper, we explore the ways in which Internet routing policies impact RTT measurements by illustrating with real examples from the current Internet In particular, we investigate how Internet routing policies for both intra- and inter-domain routing can naturally give rise to violations of the triangle inequality with respect to RTTs. Triangle Inequality Violations (TIVs) might be exploited by overlay routing to set up end-to-end overlay forwarding paths with reduced latencies and better Quality of Service (QoS) if these overlay forwarding paths can be stitched together with network paths routed at layer 3. We argue that TIVs should not be treated as measurement artifacts, but rather as natural features of the Internet's structure. In addition to explaining Internet routing policies that give rise to TIVs, we present real illustrating examples from the current Internet.