# NetChain: Scale-Free Sub-RTT Coordination (Extended Version)

## TL;DR

NetChain leverages programmable switches to achieve sub-RTT, scale-free coordination in datacenters, significantly reducing latency and increasing throughput compared to traditional server-based solutions.

## Contribution

This paper introduces NetChain, a novel network-based coordination approach using programmable switches for low-latency, high-throughput, and fault-tolerant distributed coordination.

## Key findings

- Achieves end-to-end latency as low as half an RTT.
- Provides orders of magnitude higher throughput than ZooKeeper.
- Handles switch failures efficiently.

## Abstract

Coordination services are a fundamental building block of modern cloud systems, providing critical functionalities like configuration management and distributed locking. The major challenge is to achieve low latency and high throughput while providing strong consistency and fault-tolerance. Traditional server-based solutions require multiple round-trip times (RTTs) to process a query. This paper presents NetChain, a new approach that provides scale-free sub-RTT coordination in datacenters. NetChain exploits recent advances in programmable switches to store data and process queries entirely in the network data plane. This eliminates the query processing at coordination servers and cuts the end-to-end latency to as little as half of an RTT---clients only experience processing delay from their own software stack plus network delay, which in a datacenter setting is typically much smaller. We design new protocols and algorithms based on chain replication to guarantee strong consistency and to efficiently handle switch failures. We implement a prototype with four Barefoot Tofino switches and four commodity servers. Evaluation results show that compared to traditional server-based solutions like ZooKeeper, our prototype provides orders of magnitude higher throughput and lower latency, and handles failures gracefully.