Connection-level Models

In this chapter, we study simple models of the dynamics of a network at the connection level, i.e., at the level of file arrivals and departures. In all the previous chapters, we assumed that the number of controlled flows in the network is a constant and studied the congestion control and resource allocation problem for a fixed number of flows. In reality, connections or files or flows arrive and depart from the network. We assume that the amount of time that it takes for the congestion control algorithms to drive the source rates close to their equilibrium is much smaller than the inter-arrival and inter-departure times of files. In fact, we assume that compared to the time-scale of connection dynamics, the congestion control algorithm operates instantaneously, providing a resource allocation dictated by the utility functions of the users of the network. In the following sections of this chapter, we will study the impact of flow-level resource allocation on connection-level stochastic stability for this time-scale separated model.