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The controller will be modified to expose both of the endpoints so that older servers will be able to work with the newer controllers.
The existing controller endpoint for a single-step commit will be modified to extract the segment metadata and segment creation metadata if there are three parts in the uplload.
The servers will support a configuration mechanism so that the servers will use the new mechanism in this proposal only if configured to do so. This configuration can ensure backward compatibility if servers are upgraded before controllers.
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