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RFC 9957 - The DOCSIS Queue Protection Algorithm to Preserve Low Latency

  • Status: Informational
  • Published: May 2026
  • Stream: INDEPENDENT
  • Errata: No Errata

Abstract​

This Informational RFC explains the specification of the queue protection algorithm introduced into Data-Over-Cable Service Interface Specification (DOCSIS) technology at version 3.1. A shared low-latency queue relies on the non-queue-building behaviour of every traffic flow using it. However, some flows might not take such care, either accidentally or maliciously. If a queue is about to exceed a threshold level of delay, the Queue Protection algorithm can rapidly detect the flows most likely to be responsible. It can then prevent harm to other traffic in the low-latency queue by ejecting selected packets (or all packets) of these flows. This document is designed for four audiences: a) congestion control designers who need to understand how to keep on the "good" side of the algorithm; b) implementers of the algorithm who want to understand it in more depth; c) designers of algorithms with similar goals, perhaps for non-DOCSIS scenarios; and d) researchers interested in evaluating the algorithm.

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