1. Introduction

QProt protects traffic in a shared Low-Latency (LL) queue from flows that accidentally or maliciously behave in a queue-building way. In normal scenarios without misclassified traffic, QProt is not expected to intervene.

DOCSIS low-latency support uses two queues in each direction: Low-Latency and Classic. QProt is located at the ingress to the LL queue: upstream on the Cable Modem (CM), downstream on the CM Termination System (CMTS). When a packet triggers queue protection, the DOCSIS action is to eject it from LL and reclassify it into the Classic queue.

This Informational RFC does not override the DOCSIS specifications; if inconsistent, DOCSIS takes precedence.

Terminology: CM, CMTS, DOCSIS, QProt, ECN, Congestion Experienced (CE), Low-Latency (LL), Classic, queue-building, non-queue-building, Non-Queue-Building (NQB), L4S, probNative, qdelay, qLscore, AGING.