This read-write value selects which of two egress port queues, high priority or low priority, a Frame Relay channel's traffic is mapped to, defaulting to the high-priority queue, with notSupported(3) used on cards like FRSM-VHS where chanServType determines queue mapping instead. An administrator assigns delay-sensitive or business-critical PVCs to the high-priority queue and bulk or best-effort traffic to the low-priority queue to control which gets serviced first during congestion. On an FRSM12 card, this same object instead selects between the two ATM Class-of-Service queues on the egress side, reflecting that card's different underlying queue architecture.