Sprinklers: A Randomized Variable-Size Striping Approach to Reordering-Free Load-Balanced Switching

TL;DR

Sprinklers is a novel load-balanced switch design that guarantees packet order by assigning each virtual output queue to a specific path, achieving near-perfect load balancing with low implementation complexity.

Contribution

The paper introduces Sprinklers, a new load-balanced switch architecture that ensures packet order without complex matching, using randomized path assignment and proportional 'fatness' for VOQs.

Findings

Achieves near-perfect load balancing under arbitrary traffic.

Guarantees packet order within each VOQ.

Uses novel large deviation techniques for rigorous analysis.

Abstract

Internet traffic continues to grow exponentially, calling for switches that can scale well in both size and speed. While load-balanced switches can achieve such scalability, they suffer from a fundamental packet reordering problem. Existing proposals either suffer from poor worst-case packet delays or require sophisticated matching mechanisms. In this paper, we propose a new family of stable load-balanced switches called "Sprinklers" that has comparable implementation cost and performance as the baseline load-balanced switch, but yet can guarantee packet ordering. The main idea is to force all packets within the same virtual output queue (VOQ) to traverse the same "fat path" through the switch, so that packet reordering cannot occur. At the core of Sprinklers are two key innovations: a randomized way to determine the "fat path" for each VOQ, and a way to determine its "fatness" roughly in proportion to the rate of the VOQ. These innovations enable Sprinklers to achieve near-perfect load-balancing under arbitrary admissible traffic. Proving this property rigorously using novel worst-case large deviation techniques is another key contribution of this work.