This read-write VlanPriority is the specific Exp value used on the network port to represent a priority with implicit drop-ineligibility encoded into it. An administrator configures it so that traffic meant to be protected from discard is unambiguously marked as such once translated into the MPLS Exp field. For example, setting this to Exp value 6 means frames encoded with that value are recognized as drop-ineligible priority-6 traffic by any downstream node reading the Exp bits.