The effect of uncertain time variant delays in ATM networks with explicit rate feedback

A new, more realistic model for the ABR traffic class in ATM network congestion control is introduced and analyzed. The new discrete time model takes into account the effect of time-variant buffer occupancy levels of ATM switches, thus treating the case of time-variant delays between a single congested node and the connected sources. For highly dynamic situations, such a model is crucial for a valid analysis of the resulting feedback system. The new model also handles the effects of the mismatch between the RM cell rates and the variable bit rate controller sampling rate as well as buffer and rate nonlinearities. A stability study is presented, that shows an equilibrium in the buffer occupancy level is not possible if time-variant delays are present in the forward path. Stability conditions for the case of time-variant delays in the return path are derived. Finally, illustrating examples are provided.