ERA: Meeting the Fairness between Sender-driven and Receiver-driven Transmission Protocols in Data Center Networks

The modern data centers require high throughput and low latency transmission to meet the demands of distributed applications on communication delay. Compared with traditional sender-driven try-and-back-off protocols (e.g., TCP and its variants), receiver-driven protocols (RDPs) achieve the ultra-low transmission latency by reacting to credits or tokens from receivers. However, RDPs face fairness challenges when coexisting with sender-driven protocols (SDPs) in multi-tenant data centers. Their flows barely survive during coexistence with SDP flows since the delicate scheduling of their credits is disrupted and overwhelmed by SDP data packets. To tackle this issue, we propose the Equivalent Rate Adaptor (ERA), a scheme that converts the proactive try-and-back-off mode of SDPs to an RDP-like credit-based reactive mode. ERA leverages the advertised window field in ACK headers at the receiver side to elaborately limit the number of the in-flight packets or bytes in SDPs and thus reduce their impacts on RDPs. Therefore, ERA not only ensures the fairness between two different types of protocols, but also maintains the low latency feature of RDPs. Moreover, ERA is lightweight, flexible, and transparent to tenants by embedding into the prevalent Open vSwitch in the public cloud. The evaluation of both test-bed and NS2 simulation shows that ERA enables SDP flows and RDP flows to maintain good throughput and share the bandwidth fairly, improving the bandwidth stolen by up to 94.29%.