Internet Routing Policies and Round-Trip-Times
Han Zheng
Round trip times (RTTs) play an important role in Internet
measurements. In this talk, we explore some of the ways in which
routing policies impact RTTs. In particular, we investigate how
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 if an end-to-end forwarding path can be
stitched together with paths routed at layer 3. However, TIVs pose a
problem for Internet Coordinate Systems that attempt to associate
Internet hosts with points in Euclidean space so that RTTs between
hosts are accurately captured by distances between their associated
points. Three points having RTTs that violate the triangle inequality
cannot be embedded into Euclidean space without some level of
inaccuracy. 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 routing policies that give rise to TIVs, we
present illustrating examples from the current Internet.
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