Jose Barreto comments on his TechNet blog:
Note: This blog post is a Windows Server 2012 R2 update on a previous version focused on Windows Server 2012.
With the release of Windows 8.1 and Windows Server 2012 R2, I am frequently asked about how older versions of Windows will behave when connecting to or from these new versions. Upgrading to a new version of SMB is something that happened a few times over the years and we established a process in the protocol itself by which clients and servers negotiate the highest version that both support.
Read up for a good primer on the various versions of the SMB protocol. And whatever you do, don’t call it CIFS!
Read more at: Windows Server 2012 R2: Which version of the SMB protocol (SMB 1.0, SMB 2.0, SMB 2.1, SMB 3.0 or SMB 3.02) you are using?
[…] = iSCSI or NFS target. Sadly FreeNAS doesn’t do SMB 3.0 yet (Indeed, they still call it CIFS, a violation  of the rules!), so experimenting with that kickass storage spec (EMC says it’s the future of storage […]