Reducing Latency in Multi-Tenant Data Centers via Cautious Congestion Watch
Ahmed M. Abdelmoniem, Hengky Susanto, Brahim Bensaou · 2020
Modern data centers host a plethora of interactive data-intensive applications. These are known to often generate large numbers of short-lived parallel flows that must complete their transfer quickly to meet the stringent performance requirements of interactive applications. Network resources (e.g., switch buffer space) in the data center are scarce and are easily congested, which unfortunately results in long latency. As a first solution, following a traditional design rationale, Data Center TCP (DCTCP) was proposed to speed up the completion time of short-lived flow by maintaining a low buffer occupancy in the switch. In general, DCTCP performs well in homogeneous environments, however, its performance degrades quickly in heterogeneous environments or when it uses a large initial congestion window. To resolve this problem, we propose a Hypervisor-based congestion watching mechanism (HWatch), which measures the network load in the data center via ECN and uses the resulting statistics to determine the appropriate initial congestion window size to avoid congestion. HWatch neither needs modification to the TCP stack in the VMs nor requires any specialized network hardware features to meet its targets. In our evaluation, we demonstrate the benefits of HWatch in improving the performance of TCP flows through large-scale ns2 simulation and via testbed experiments in a small data center.