  This memo focuses solely on the native AQM of Low Latency Low Loss Scalable
throughput (L4S) traffic and proposes various improvements to the original step
design. One motivation for DCTCP to use simple step marking was that it was
possible to deploy it by merely configuring the RED implementations in existing
hardware, albeit in an unexpected configuration by setting parameters to
degenerate values. However, there is no longer any imperative to stick with the
original DCTCP step-function design, because changes will be needed to
implement the DualQ Coupled AQM anyway, and the requirements for L4S congestion
controls are not yet set in stone either. This paper proposes gradient (ramp)
marking and a virtual (a.k.a. phantom) queue. It provides a way to implement
virtual queuing delay (a.k.a. virtual sojourn time) and scaled virtual sojourn
time.
