FNCC: Fast Notification Congestion Control in Data Center Networks

TL;DR

FNCC introduces a sub-RTT notification mechanism using in-network telemetry and receiver feedback, significantly reducing flow completion times and improving data center network congestion control responsiveness.

Contribution

The paper presents FNCC, a novel congestion control method achieving sub-RTT notification and faster response in data center networks, outperforming existing algorithms.

Findings

Reduces flow completion time by 27.4% compared to HPCC.

Reduces flow completion time by 88.9% compared to DCQCN.

Maintains high utilization at 400Gbps with minimal pause frames.

Abstract

Congestion control plays a pivotal role in large-scale data centers, facilitating ultra-low latency, high bandwidth, and optimal utilization. Even with the deployment of data center congestion control mechanisms such as DCQCN and HPCC, these algorithms often respond to congestion sluggishly. This sluggishness is primarily due to the slow notification of congestion. It takes almost one round-trip time (RTT) for the congestion information to reach the sender. In this paper, we introduce the Fast Notification Congestion Control (FNCC) mechanism, which achieves sub-RTT notification. FNCC leverages the acknowledgment packet (ACK) from the return path to carry in-network telemetry (INT) information of the request path, offering the sender more timely and accurate INT. To further accelerate the responsiveness of last-hop congestion control, we propose that the receiver notifies the sender of the number of concurrent congested flows, which can be used to adjust the congested flows to a fair rate quickly. Our experimental results demonstrate that FNCC reduces flow completion time by 27.4% and 88.9% compared to HPCC and DCQCN, respectively. Moreover, FNCC triggers minimal pause frames and maintains high utilization even at 400Gbps.