"Issues with Inferring Internet Topological Attributes"
Lisa Amini, Anees Shaikh, and Henning Schulzrinne
A number of recent studies are based on data collected from routing
tables of inter-domain routers utilizing Border Gateway Protocol (BGP)
and tools, such as traceroute, to probe end-to-end paths. The goal is
to infer Internet topological properties. However, as more data is
collected, it becomes obvious that data intended to represent the same
properties, if gathered at different points within the network, can
depict significantly different characteristics. While systematic data
collection from a number of network vantage points can reduce certain
ambiguities, thus far, no methods have been reported for fully
resolving these issues. The goal of our study was to quantify the
effect these anomalies have on key Internet structural attributes. We
report on our analysis of over 290,000 measurements from globally
distributed sites. We contrast results obtained from router-level
measurements with those obtained from BGP routing tables, and offer
insights as to why certain inferred properties differ. We demonstrate
that the effect on some attributes, such as the average path length
and the AS degree distribution can be minimized through careful data
collection techniques. We also illustrate how using this same data to
model other attributes, such as the actual forwarding path between a
pair of nodes, or the level of AS path asymmetry, can produce
substantially misleading results.