This sets the service priority, from 0 (highest) to 15 (lowest), of this specific traffic shaper entry, where channels assigned to it are only served once no higher-priority shaper on this port has traffic waiting. Because lower-numbered shapers here strictly preempt higher-numbered ones on this specific port, a shaper left at priority 0 for anything other than truly critical traffic risks starving every other shaper on the same port whenever it has cells to send, regardless of how modest its actual configured rate is. Assigning voice traffic to shaper priority 0 and bulk data traffic to priority 10 on this port ensures the bulk data only gets served during moments when the voice shaper has no cells waiting.