Spritz: Path-Aware Load Balancing in Low-Diameter Networks

Fuente: arXiv
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Main Authors: Bonato, Tommaso, Kubicek, Ales, Kabbani, Abdul, Ghalayini, Ahmad, Besta, Maciej, Hoefler, Torsten
Format: Preprint
Published: 2026
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author Bonato, Tommaso
Kubicek, Ales
Kabbani, Abdul
Ghalayini, Ahmad
Besta, Maciej
Hoefler, Torsten
author_facet Bonato, Tommaso
Kubicek, Ales
Kabbani, Abdul
Ghalayini, Ahmad
Besta, Maciej
Hoefler, Torsten
contents Low-diameter topologies such as Dragonfly and Slim Fly are increasingly adopted in HPC and datacenter networks, yet existing load balancing techniques either rely on proprietary in-network mechanisms or fail to utilize the full path diversity of these topologies. We introduce Spritz, a flexible sender-based load balancing framework that shifts adaptive topology-aware routing to the endpoints using only standard Ethernet features. We propose two algorithms, Spritz-Scout and Spritz-Spray that, respectively, explore and adaptively cache efficient paths using ECN, packet trimming, and timeout feedback. Through simulation on Dragonfly and Slim Fly topologies with over 1000 endpoints, Spritz outperforms ECMP, UGAL-L, and prior sender-based approaches by up to 1.8x in flow completion time under AI training and datacenter workloads, while offering robust failover with performance improvements of up to 25.4x under link failures, all without additional hardware support. Spritz enables datacenter-scale, commodity Ethernet networks to efficiently leverage low-diameter topologies, offering unified routing and load balancing for the Ultra Ethernet era.
format Preprint
id arxiv_https___arxiv_org_abs_2602_19567
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Spritz: Path-Aware Load Balancing in Low-Diameter Networks
Bonato, Tommaso
Kubicek, Ales
Kabbani, Abdul
Ghalayini, Ahmad
Besta, Maciej
Hoefler, Torsten
Networking and Internet Architecture
Low-diameter topologies such as Dragonfly and Slim Fly are increasingly adopted in HPC and datacenter networks, yet existing load balancing techniques either rely on proprietary in-network mechanisms or fail to utilize the full path diversity of these topologies. We introduce Spritz, a flexible sender-based load balancing framework that shifts adaptive topology-aware routing to the endpoints using only standard Ethernet features. We propose two algorithms, Spritz-Scout and Spritz-Spray that, respectively, explore and adaptively cache efficient paths using ECN, packet trimming, and timeout feedback. Through simulation on Dragonfly and Slim Fly topologies with over 1000 endpoints, Spritz outperforms ECMP, UGAL-L, and prior sender-based approaches by up to 1.8x in flow completion time under AI training and datacenter workloads, while offering robust failover with performance improvements of up to 25.4x under link failures, all without additional hardware support. Spritz enables datacenter-scale, commodity Ethernet networks to efficiently leverage low-diameter topologies, offering unified routing and load balancing for the Ultra Ethernet era.
title Spritz: Path-Aware Load Balancing in Low-Diameter Networks
topic Networking and Internet Architecture
url https://arxiv.org/abs/2602.19567