AuthorsB. Briscoe, K. De Schepper, and M. Bagnulo
TitleLow Latency, Low Loss, Scalable Throughput (L4S) Internet Service: Problem Statement
AfilliationCommunication Systems
Project(s)TimeIn: Traffic behaviour of interactive time-dependent thin streams on the modern Internet
Publication TypeTechnical reports
Year of Publication2016
Date Published07/2016
PublisherInternet Engineering Task Force
KeywordsAlgorithms, Analysis, AQM, Congestion Avoidance, congestion control, Data Communication, Design, Evaluation, Internet, latency, networks, Performance, QoS, Scaling, tcp

This document motivates a new service that the Internet could provide to eventually replace best efforts for all traffic: Low Latency, Low Loss, Scalable throughput (L4S).  It is becoming common for all (or most) applications being run by a user at any one time to require low latency.  However, the only solution the IETF can offer for ultra-low queuing delay is Diffserv, which only favours a minority of packets at the expense of others.  In extensive testing the new L4S service keeps average queuing delay under a millisecond for all applications even under very heavy load, without sacrificing utilization; and it keeps congestion loss to zero.  It is becoming widely recognized that adding more access capacity gives diminishing returns, because latency is becoming the critical problem.  Even with a high capacity broadband access, the reduced latency of L4S remarkably and consistently improves performance under load for applications such as interactive video, conversational video, voice, Web, gaming, instant messaging, remote desktop and cloud-based apps (even when all being used at once over the same access link).  The insight is that the root cause of queuing delay is in TCP, not in the queue.  By fixing the sending TCP (and other transports) queuing latency becomes so much better than today that operators will want to deploy the network part of L4S to enable new products and services. Further, the network part is simple to deploy - incrementally with zero-config.  Both parts, sender and network, ensure coexistence with other legacy traffic.  At the same time L4S solves the long-recognized problem with the future scalability of TCP throughput.

This document explains the underlying problems that have been preventing the Internet from enjoying such performance improvements. It then outlines the parts necessary for a solution and the steps that will be needed.


(Work in Progress)

Citation Key25063