  Models for the dynamics of congestion control generally involve systems of
coupled differential equations. Universally, these models assume that traffic
sources saturate the maximum transmissions allowed by the congestion control
method. This is not suitable for studying congestion control of intermittent
but bursty traffic sources. In this paper, we present a characterization of
congestion control for arbitrary time-varying traffic that applies to
rate-based as well as window-based congestion control. We leverage the
capability of network calculus to precisely describe the input-output
relationship at network elements for arbitrary source traffic. We show that our
characterization can closely track the dynamics of even complex congestion
control algorithms.
