A Gateway Proxy with ECN Buffer Control for Inter-Datacenter Congestion Control

Abstract

In a data center (DC) where inter- and intra-DC flows share high-speed data center networks (DCNs), these two types of flows have significantly different round-trip times (RTTs). When congestion occurs in a DCN, the congestion signal is detected first by the intra-DC flow, resulting in unfairness where only it reacts to congestion. This technical problem is especially important for the receiving DCN because the congestion point is far from the sender. To solve this issue, we propose DC performance enhancing proxy (DC-PEP) with ECN (Explicit Congestion Notification) buffer control as a proxy at the gateway of the receiving DCN. DC-PEP divides the end-to-end congestion control loop into two loops, which homogenizes the congestion loop inside the receiving DCN. To absorb the throughput difference between these two congestion loops, a buffer is required at DC-PEP. By implementing ECN-Echo notification, excessive queueing at DC-PEP can be avoided. Our simulation results show that our proposed DC-PEP with ECN improves fairness between inter- and intra-DC flows without incurring large queue sizes at the proxy.