  In this paper the chaotic properties of the TCP congestion avoidance
mechanism are investigated. The analysis focuses on the origin of the complex
behavior appearing in deterministic TCP/IP networks. From the traffic modeling
point of view the understanding of the mechanism generating chaos is essential,
since present models are unable to cope with this phenomena. Using the basic
tools of chaos theory in our study, the main characteristics of chaotic
dynamics are revealed. The dynamics of packet loss events is studied by a
simple symbolic description. The cellular structure of the phase space of
congestion windows is shown. This implies periodic behavior for large time
scales. Chaotic behavior in short time scales and periodicity for larger times
makes it necessary to develop models that account for both. Thus a simple model
that describes the congestion window dynamics according to fluid equations, but
handles the packet loss events separately is introduced. This model can
reproduce the basic features observed in realistic packet level simulations.
