The management of communication networks increasingly requires
detailed knowledge of network usage, acquired by direct measurement.
We report on the design and implementation of a backend system for
Trajectory Sampling, a method for consistent sampling of packets
across a network domain. This Trajectory Engine
collects trajectory samples and stores them
after appropriate preprocessing. It provides a querying
and visualization tool to aid in traffic engineering and
troubleshooting.
We describe the entire system, and in particular the
design choices that we took in order to balance the scale of system
(due to large volumes of measured data) with resource usage while
providing useful functionality for users. In the preprocessing
stage, we focus on reassembly of trajectories from individual
samples. We describe the design of the database for efficient
storage of trajectories, and its relationship with the query and
visualization interface. We test the system using a synthetic
stream of trajectory samples derived from configuration and usage
data from the network of a major service provider. We walk
through several examples that illustrate how a network operator
might take advantage of trajectory sampling through such a tool.
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