A. There's no specific encryption used for CSV traffic, but if you've implemented IPSEC, IPSEC encryption is used for CSV data and all other intra-cluster communication.

See also:
How do I create a failover cluster in Windows Server 2008?
Is a Windows Server 2003 and Windows Server 2008 mixed-cluster possible?
How can I add disk resources to a Windows Server 2008 cluster from the command line?
How do cluster shared volumes work in Windows Server 2008 R2?

How to Manage Failover Clusters in Windows Server 2008
Configure Windows Server 2008 Failover Clustering from the Command Line

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