R3303-HP HSR6800 Routers ACL and QoS Configuration Guide

140
Figure 51 Implementing 4-level HQoS scheduling through nesting QoS polices
As shown in Figure 51, start the HQoS scheduling through nesting QoS policies on the interfaces. The
HQoS scheduling operates in the following workflow:
1. First, the classes in the parent QoS policy is used to differentiate users, and the corresponding
actions are performed for the users.
2. Then, the classes of the child QoS policy are used to differentiate services, and actions such as
expedited forwarding (EF), assured forwarding (AF), best-effort (BE), committed access rate (CAR),
traffic filtering, and generic traffic shaping (GTS) are performed for the corresponding classes,
respectively.
3. After the parent QoS policy and child QoS policy process the packet, line rate is performed for
packets, and round robin (RR) scheduling is performed among interfaces to send packets out
different interfaces.
Implementing HQoS through interface-level hierarchical CAR
CAR rate-limits the specific traffic flows. CAR polices the rate of traffic entering the network, and uses the
token bucket to color the packets processed by CAR. The token bucket size is committed burst size (CBS)
+ excess burst size (EBS). The system puts tokens into the token bucket at the rate of committed
information rate (CIR). When the system forwards packets, if the token bucket has enough tokens for
forwarding the packets and the traffic rate is lower than the CIR, the system colors the packets green and
performs the action for green packets (including marking priority, forwarding, and proceeding with the
next CAR action); if the token bucket does not have enough tokens for forwarding the packets and the