This option allows the NFS client and server to support an RDMA-enabled transport. To compile RPC client RDMA transport support as a module, choose M here: the module will be called xprtrdma. If unsure, say N.
Choose Y here to enable Secure RPC using the Kerberos version 5 GSS-API mechanism (RFC 1964). Secure RPC calls with Kerberos require an auxiliary user-space daemon which may be found in the Linux nfs-utils package available from http://linux-nfs.org/. In addition, user-space Kerberos support should be installed. If unsure, say Y.