A network engineer is reviewing the QoS configuration on a branch router's WAN uplink, which connects to a service provider with a contracted rate of 50 Mbps on a physical GigabitEthernet interface. The provider drops any traffic exceeding 50 Mbps. During peak hours, users report choppy voice quality and TCP application retransmissions, and the interface counters show a high number of drops on outbound traffic bursts. Which QoS mechanism should the engineer apply on the egress WAN interface to best address this problem?