Hierarchical QoS allows you to specify QoS behavior at multiple policy levels, which provides a high degree of granularity in traffic management. A hierarchical policy is a QoS model that enables you to specify QoS behavior at multiple levels of hierarchy. https://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/asr9k_r4- 2/qos/configuration/guide/qc42hqos.html#wp1236859