GlusterFS client 3.4.0.57 cannot mount a volume from GlusterFS server 3.2.7.1, why?

Issue

• After updating the RHEL6 client machines running GlusterFS 3.2 to 3.4, its not possible to mount the volumes from a machine with GlusterFS 3.2 packages, why? After downgrading the client to version 3.2, the mount was successful.