Resolving Tensions between Congestion Control Scaling Requirements

TL;DR

This paper analyzes the conflicting scalability requirements of L4S congestion controllers to guide the development of a new Internet service that balances low latency, low loss, and scalable throughput.

Contribution

It provides a structured analysis of the steady-state scalability constraints for L4S congestion control, informing pre-standardization consensus.

Findings

Identifies key conflicts in scalability requirements

Offers a framework for resolving these conflicts

Guides future L4S congestion control design

Abstract

Low Latency, Low Loss Scalable throughput (L4S) is being proposed as the new default Internet service. L4S can be considered as an `incrementally deployable clean-slate' for new Internet flow-rate control mechanisms. Because, for a brief period, researchers are free to develop host and network mechanisms in tandem, somewhat unconstrained by any pre-existing legacy. Scaling requirements represent the main constraints on a clean-slate design space. This document confines its scope to the steady state. It aims to resolve the tensions between a number of apparently conflicting scalability requirements for L4S congestion controllers. It has been produced to inform and provide structure to the debate as researchers work towards pre-standardization consensus on this issue. This work is important, because clean-slate opportunities like this arise only rarely and will only be available briefly---for roughly one year. The decisions we make now will tend to dirty the slate again, probably for many decades.