Sizing router buffer for the Internet with heterogeneous TCP

The router buffer sizing problem is a vital problem to the performance of the Internet. The traditional rule-of-thumb is that the router buffer size should be equal to the bandwidth-delay product (BDP) of a link. Recent studies show that the router buffer size can be significantly smaller than the BDP without causing negative impact on the TCP performance in the Internet. But a fundamental assumption of all those studies is that all the TCP traffic in the Internet is generated by the traditional RENO protocol, which, however, is no longer true as the current Internet is dominated by multiple different TCP protocols, such as RENO, CUBIC and Compound TCP (CTCP). Thus, it is imperative that we revisit the router buffer sizing problem for the Internet with heterogeneous TCP. In this paper, we propose methods to determine the router buffer size requirements under various constraints for the Internet with heterogeneous TCP and discuss the tradeoff among the constraints. The constraints considered include the link utilization constraint, the packet drop rate constraint, and the queuing delay constraint. Our study shows that the required router buffer size can be significantly smaller than the BDP but also demonstrates that it is dependent on the protocol mix of the heterogeneous TCP flows.