Spectral Probing, Crosstalk And Frequency Multiplexing In Internet Paths

We present an end-to-end active probing methodology that creates frequency-domain signals in IP network paths. The signals are generated by periodic packet trains that cause short-lived queueing delay spikes. Different probers can be multiplexed in the frequency-domain on the same path. Further, a signal that is introduced by a "prober" in one path can cause a crosstalk effect, inducing a signal of the same frequency into another path (the "sampler") as long as the two paths share one or more bottleneck queues. Applications of the proposed methodology include the detection of shared store-and-forward devices among two or more paths, the creation of covert channels, and the modulation of voice or video periodic packet streams in less noisy frequencies. In this paper we focus on the first application. Our goal is to detect shared bottleneck(s) between a "sampler" and one or more "prober" paths. We present a spectral probing methodology as well as the corresponding signal processing/detection process. The accuracy of the method has been evaluated with controlled and repeatable simulation experiments, and it has also been tested on some Internet paths.