Epic Goal

We already support to  lower the cluster-wide MTU to the Lowest Common Denominator one. We will do a design spike to investigate per path MTU and look to implement the same.

Why is this important?

• Issues on nodes in a different ROSA Local Zone
• MTU is calculated based on what the Geneve overhead is
• We use the MTU of the first node (if they did not specify one in the cluster config) minus the header overhead
• We taint nodes whose MTU is too small and the node won’t go ready

• You can change the MTU on a running cluster, so they can shrink down the MTU if needed
• Perfscale has tested with 9k MTU, lowering the MTU will cost more

Scenarios

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Acceptance Criteria

• CI - MUST be running successfully with tests automated
• Release Technical Enablement - Provide necessary release enablement details and documents.
• ...

Dependencies (internal and external)

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Previous Work (Optional):

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Open questions::

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Done Checklist

• CI - CI is running, tests are automated and merged.
• Release Enablement <link to Feature Enablement Presentation>
• DEV - Upstream code and tests merged: <link to meaningful PR or GitHub Issue>
• DEV - Upstream documentation merged: <link to meaningful PR or GitHub Issue>
• DEV - Downstream build attached to advisory: <link to errata>
• QE - Test plans in Polarion: <link or reference to Polarion>
• QE - Automated tests merged: <link or reference to automated tests>
• DOC - Downstream documentation merged: <link to meaningful PR>