4.2.9 Independent mechanism for verifying the integrity of the content
From CLOCKSS Trusted Digital Repository Documents
4.2.9 - The repository shall provide an independent mechanism for verifying the integrity of the repository collection/content.
As described in CLOCKSS: Box Operations the CLOCKSS boxes are configured to form a Private LOCKSS Network (PLN). The boxes run the LOCKSS: Polling and Repair Protocol which regularly compares the content of an AU at one box with the content of the same AU at other boxes, and resolves any discrepancies.