FluNet: A hybrid internet simulator for fast queue regimes

Motivated by the scale and complexity of simulating large-scale networks, recent research has focused on hybrid fluid/packet simulators, where fluid models are combined with packet models in order to reduce simulation complexity as well as to track dynamics of end-sources accurately. However, these simulators still need to track the queuing dynamics of network routers, which generate considerable simulation complexity in a large-scale network model. In this paper, we propose a new hybrid simulator – FluNet – where queueing dynamics are not tracked. The FluNet simulator is predicated on a fast-queueing regime at bottleneck routers, where the queue length fluctuates on a faster time-scale than end systems. FluNet does not track queue lengths at routers, but instead, replaces queue-based AQM schemes (such as RED or DropTail) by an equivalent rate-based model. This allows us to simulate large-scale systems, where the simulation “time step-size” is governed only by the timescale of the end-systems, and not by that of the intermediate routers; whereas a fluid model based simulator that tracks queue-length would require decreasingly smaller step-sizes as the system scale size (such as the number of flows and link capacity) increases. We validate our model using a ns-2 based implementation. Our results indicate a good match between packet systems and the associated FluNet system.