This boolean switches on matching against the outer 802.1Q Priority Code Point (PCP) -- the 3-bit class-of-service marking in a VLAN tag -- letting a rule filter traffic based on its priority marking on the outer tag rather than any address or port field. An admin uses PCP-based ACL matching to build QoS-aware security policy, for instance treating traffic marked at a high-priority PCP value differently from best-effort traffic, when this is set true alongside populating cienaCesAclRuleOuterPcp. For example, an admin concerned about a device improperly self-marking its own traffic as high-priority might write a rule matching PCP value 7 on a specific untrusted port and deny it, forcing that device's traffic to be re-marked by trusted equipment instead.