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Lost in the Layers - Scaling OVN-Kubernetes User-Defined Networks from K8S API to the kernel#

Open vSwitch and OVN 2026 Fall Conference digest Program Core pick 2–4 November 2026

Abstract

Patryk Diak, Red Hat, LLC.; Dumitru Ceara, Red Hat, LLC.

  • Why: The canonical modern debugging story — a scaling problem that turned out to be distributed across every layer of the stack. This is exactly the kind of full-stack triage (K8s API → OVN NB/SB → OVS flows → kernel) the PM's world runs on, and the "telemetry we wish we'd had" is directly reusable.
  • What: A postmortem-style account of scaling OVN-Kubernetes UDN workloads in which every layer contributed a small failure, and all of them had to be fixed before any improvement was visible. The core finding: most engineering time went to localizing the failing layer, not to fixing it. (from abstract only)
  • How: Systematic per-layer bisection from the Kubernetes API server down to the kernel, with a retrospective on the observability gaps that made attribution slow.
  • Where applicable: General to any OVN-Kubernetes deployment pushing UDN density; the telemetry recommendations transfer to any layered CNI debugging. Not tied to a particular operator's scale, though the pain obviously grows with network count.