Volume-Based Transit Pricing: Is 95 the Right Percentile?

The 95

th

percentile billing mechanism has been an industry

de facto

standard for transit providers for well over a decade. While the simplicity of the scheme makes it attractive as a billing mechanism, dramatic evolution in traffic patterns, associated interconnection practices and industry structure over the last two decades motivates an obvious question: is it still appropriate? In this paper, we evaluate the 95

th

percentile pricing mechanism from the perspective of transit providers, using a decade of traffic statistics from SWITCH (a large research/academic network), and more recent traffic statistics from 3 Internet Exchange Points (IXPs). We find that over time, heavy-inbound and heavy-hitter networks are able to achieve a lower 95th-to-average ratio than heavy-inbound and moderate-hitter networks, possibly due to their ability to better manage their traffic profile. The 95

th

percentile traffic volume also does not necessarily reflect the cost burden to the provider, motivating our exploration of an alternative metric that better captures the costs imposed on a network. We define the

provision ratio

for a customer, which captures its contribution to the provider’s peak load.