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“Measurements-in-the-middle”: Inferring end-end path properties and characteristics of TCP connections through passive measurements

Sharad Jaiswal, University of Massachusetts Amherst


We propose a methodology to infer end-end path properties of TCP connections (such as packet loss, reordering and delay) and other factors that affect TCP sender behavior using passive measurements collected at a single point of observation along the end-end path. With this passive approach, an observation point in a Tier-1 backbone network can observe and analyze millions of TCP connections, which originate and terminate from a highly diverse cross-section of end points in today's Internet - a capability that is unmatched by current active measurement techniques. We apply our passive measurement inference techniques on traces collected in a large Tier-1 backbone network. We analyze the causes of out-of-sequence packets (due to loss, reordering and in-network duplication), the distribution and variation of round-trip delay, the congestion control flavors of TCP, and the extent to which application-level considerations limit TCP throughput. We validate the accuracy of our measurement-based inference techniques by comparing inferred behavior with active measurements made on monitored flows. But empirical validation alone is insufficient, since monitored paths can exhibit a wide range of network properties, many of which may occur only rarely. Thus, we use a combination of model-checking and formal reasoning to identify all possible events in the network for which the inference rules can produce incorrect results.

Subject Area

Computer science

Recommended Citation

Jaiswal, Sharad, "“Measurements-in-the-middle”: Inferring end-end path properties and characteristics of TCP connections through passive measurements" (2005). Doctoral Dissertations Available from Proquest. AAI3193912.