This read-write field selects which metric, administrative cost, end-to-end delay, or cell delay variation, the switch's path-selection logic uses specifically when routing new ATM connections assigned to QoS Class 1 across the trunk fabric. An admin picks cell-delay-variation or end-to-end-delay for class 1 when it carries the most delay and jitter-sensitive traffic, like voice, ensuring the network chooses the lowest-latency or most-consistent path for that class even if it is not the cheapest administratively. For example, setting lportAtmRouteMetricQoS1 to cell-delay-variation(3) means new voice circuits assigned to class 1 get routed over whichever available trunk path minimizes jitter, rather than simply the path with the lowest lportTrkAdminCost.