Traffic and congestion control in broadband networks

One of the main difficulties, when dimensioning a telecommunication network, is to deal with the random nature of the input traffic. The traffic control goal is to protect both the receiving terminal equipments and the network elements (e.g. multiplexers, switches, etc.) against traffic excess. Once the traffic is controlled, it becomes more predictable for the network and resource utilization can be optimized. We begin the presentation with a brief introduction to B-ISDN networks and to the ATM technique that has been retained as the transfer mode of these networks. It turns out that traffic control mechanisms that are used in existing networks are not adapted to the characteristics of high speed networks. These characteristics are mainly the high bandwidth-propagation delay product and the heterogeneity of the input traffic (voice, video, data, etc.). We present the properties that are required for traffic control mechanisms in order to be well suited to these network characteristics and the general traffic management framework of ATM networks. We finish the talk by presenting some open problems, related to preventive and reactive traffic control, that still required more research work.