Robustness of real and virtual queue based active queue management schemes

In this paper, we compare the performances of the real and virtual queue based marking schemes used at the routers in the Internet. Using simple fluid flow models, we show via an analysis and simulations that a virtual queue (VQ) based marking scheme is superior to a real queue (RQ) based marking scheme in terms of robustness to disturbances and the ability to maintain low queueing delays. Our analytical results are applicable to the combinations of proportionally-fair and TCP-type congestion controllers at the sources, and random exponential marking and proportional control at the routers. The behavior of RED is studied via simulations.