‘ Data Centre to the Home ’ : Ultra-Low Latency for All

Data Centre TCP (DCTCP) was designed to provide predictably low queuing latency, near-zero loss, and throughput scalability using explicit congestion notification (ECN) and an extremely simple marking behaviour on switches. However, DCTCP does not co-exist with existing TCP traffic— throughput starves. So, until now, DCTCP could only be deployed where a clean-slate environment could be arranged, such as in private data centres. This paper proposes ‘Coupled Active Queue Management (AQM)’ to allow scalable congestion controls like DCTCP to safely co-exist with classic Internet traffic. In extensive tests within the edge gateway of a realistic broadband access testbed, the Coupled AQM ensures that a flow runs at about the same rate whether it uses DCTCP or TCP Reno/Cubic, but without inspecting transport layer flow identifiers. DCTCP achieves sub-millisecond average queuing delay and zero congestion loss under a wide range of mixes of DCTCP and ‘classic’ broadband Internet traffic, without compromising the performance of the classic traffic. The solution also reduces network complexity and eliminates network configuration.