Deadline-Aware Datacenter TCP (D2TCP)

An important class of datacenter applications, called Online Data-Intensive (OLDI) applications, includes Web search, online retail, and advertisement. To achieve good user experience, OLDI applications operate under soft-real-time constraints (e.g., 300 ms latency) which imply deadlines for network communication within the applications. Further, OLDI applications typically employ tree-based algorithms which, in the common case, result in bursts of children-to-parent traffic with tight deadlines. Recent work on datacenter network protocols is either deadline-agnostic (DCTCP) or is deadline-aware (D-3) but suffers under bursts due to race conditions. Further, D-3 has the practical drawbacks of requiring changes to the switch hardware and not being able to coexist with legacy TCP. We propose Deadline-Aware Datacenter TCP ((DTCP)-T-2), a novel transport protocol, which handles bursts, is deadline-aware, and is readily deployable. In designing (DTCP)-T-2, we make two contributions: (1) (DTCP)-T-2 uses a distributed and reactive approach for bandwidth allocation which fundamentally enables (DTCP)-T-2's properties. (2) (DTCP)-T-2 employs a novel congestion avoidance algorithm, which uses ECN feedback and deadlines to modulate the congestion window via a gamma-correction function. Using a small-scale implementation and at-scale simulations, we show that (DTCP)-T-2 reduces the fraction of missed deadlines compared to DCTCP and D-3 by 75% and 50%, respectively.