This read-write object selects which of the port's service queues a class of traffic maps to, with defined values for the High Priority Queue, real-time VBR Queue, and non-real-time VBR/ABR Queue, plus a UBR Queue, while only four of the eight possible queues are actually in use. An administrator configures this to control how different service types are prioritized for egress scheduling on the port. For example, an engineer wanting voice-like real-time traffic to get preferential treatment would map its channel to the rtVBRQ setting rather than the UBR queue used for best-effort data.