Global synchronization protection for bandwidth sharing TCP flows in high-speed links

Abstract

In a congested network link, synchronization effects between bandwidth-sharing TCP flows cause wide queue length oscillations, which may translate into poor link utilization if insufficiently buffered. We introduce global synchronization protection (GSP), a simple extension to the ordinary operation of a tail-drop queue that safely suppresses the flow synchronization. Our minimalistic solution is well suited for scaling with leading-edge link rates: it adds only few extra operations in the fast path and does not require accelerated memory access compared to the line rate. GSP makes it easier to provide advanced control of TCP congestion in high-speed links and in low-power packet processing hardware. Using experiments with a Linux prototype of GSP we show that, despite its exclusive focus on removing global synchronization, the new scheme performs as well as far more complex active queue management (AQM) schemes like CoDel and PIE.