Quantifying Overprovisioning vs. Class-of-Service: Informing the Net Neutrality Debate

The benefit of Class-of-Service (CoS) is an important topic in the "Network Neutrality" debate. Proponents of network neutrality suggest that over-provisioning is a viable alternative to CoS. We quantify the extra capacity requirement for an over-provisioned classless (i.e., best-effort) network compared to a CoS network providing the same delay or loss performance for premium traffic. We first develop a link model that quantifies this Required Extra Capacity (REC). For realistic traffic distributions (e.g., long-range dependent), we find the REC using ns-2 simulations of the CoS and classless links. Our primary contribution is in using these link models to quantify the REC for realistic network topologies under various scenarios including "closed loop" environments with traffic generated by TCP sources that adapt to the available capacity. We show that REC can be significant even when the proportion of premium traffic requiring performance assurances is small, a situation often considered benign for the over-provisioning alternative.