AuthorsK. De Schepper, B. Briscoe and I. Tsang
TitleIdentifying Modified Explicit Congestion Notification (ECN) Semantics for Ultra-Low Queuing Delay
AfilliationCommunication Systems
Project(s)The Center for Resilient Networks and Applications
Publication TypeTechnical reports
Year of Publication2016
Date Published10/2016
KeywordsAlgorithms, Analysis, AQM, Congestion Avoidance, congestion control, Data Communication, Design, Evaluation, Internet, latency, networks, Performance, QoS, Scaling, tcp

This specification defines the identifier to be used on IP packets for a new network service called low latency, low loss and scalable throughput (L4S). It is similar to the original (or 'Classic') Explicit Congestion Notification (ECN). 'Classic' ECN marking was required to be equivalent to a drop, both when applied in the network and when responded to by a transport. Unlike 'Classic' ECN marking, for packets carrying the L4S identifier, the network applies marking more immediately and more aggressively than drop, and the transport response to each mark is reduced and smoothed relative to that for drop. The two changes counterbalance each other so that the throughput of an L4S flow will be roughly the same as a 'Classic' flow under the same conditions. However, the much more frequent control signals and the finer responses to them result in ultra-low queuing delay without compromising link utilization, even during high load. Examples of new active queue management (AQM) marking algorithms and examples of new transports (whether TCP-like or real-time) are specified separately. The new L4S identifier is the key piece that enables them to interwork and distinguishes them from 'Classic' traffic. It gives an incremental migration path so that existing 'Classic' TCP traffic will be no worse off, but it can be prevented from degrading the ultra-low delay and loss of the new scalable transports.


(Work in Progress)

Citation Key23806

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