This paper presents the packet-scale paradigm for designing end-to-end congestion control protocols for ultra-high speed networks. The paradigm discards the legacy framework of RTT-scale protocols, and instead builds upon two revolutionary foundations-that of continually probing for available bandwidth at short timescales, and that of adapting the data sending rate so as to avoid overloading the network. Through experimental evaluations with a prototype, we report high performance gains along several dimensions in high-speed networks-the steady-state throughput, adaptability to dynamic cross-traffic, RTT-fairness, and co-existence with the conventional TCP traffic mixes. The paradigm also opens up several issues that are less of a concern for traditional protocols-we summarize our approaches for addressing these.

The packet-scale paradigm is a novel framework for achieving ultra-high speed congestion control. Due to its reliance on finely-controlled inter-packet gaps, the paradigm is expected to be sensitive to transient burstiness in traffic encountered on bottleneck links. This paper uses a first-principles approach to study the impact of cross traffic burstiness on the efficiency of the packet-scale paradigm. It relies on a simple periodic on-off model for cross traffic and studies the interaction of the burstiness timescale, round-trip times, and the smoothing filters adopted by the paradigm. The analysis is validated against ns-2 simulations with a prototype. Our analysis helps gain fundamental insights on the impact of several factors.