On Minimizing the Completion Times of Long Flows over Inter-Datacenter WAN
For network operators managing inter-datacenter WAN, this work provides a practical heuristic to improve flow completion times for long flows, which are critical for distributed application performance.
The authors propose a routing heuristic (BWRH) that uses remaining flow sizes and paths to minimize worst-case completion times of long flows over inter-datacenter WAN, achieving an average optimality gap of less than 0.25% and reducing mean and tail FCT by up to 1.46× and 1.53×, respectively.
Long flows contribute huge volumes of traffic over inter-datacenter WAN. The Flow Completion Time (FCT) is a vital network performance metric that affects the running time of distributed applications and the users' quality of experience. Flow routing techniques based on propagation or queuing latency or instantaneous link utilization are insufficient for minimization of the long flows' FCT. We propose a routing approach that uses the remaining sizes and paths of all ongoing flows to minimize the worst-case completion time of incoming flows assuming no knowledge of future flow arrivals. Our approach can be formulated as an NP-Hard graph optimization problem. We propose BWRH, a heuristic to quickly generate an approximate solution. We evaluate BWRH against several real WAN topologies and two different traffic patterns. We see that BWRH provides solutions with an average optimality gap of less than $0.25\%$. Furthermore, we show that compared to other popular routing heuristics, BWRH reduces the mean and tail FCT by up to $1.46\times$ and $1.53\times$, respectively.