Processing Order For Actions In Hierarchical Policies - Cisco ASR 9000 Series Service Configuration Manual

Information About Hierarchical QoS
policy-map set-frde
The policy frpvc-policy is attached to a Frame Relay PVC, which shapes that PVC to 2 Mbps, using the
shape average command that is configured on class-default in frpvc-policy. The absence of any
user-defined classes in frpvc-policy means that all traffic matches class-default and is shaped (the entire
PVC is shaped).
Attaching the bandwidth-mgmt policy to class-default in frpvc-policy specifies how the 2 Mbps in the
PVC is allocated to a voice class, a video class, and all other traffic on the PVC. In this case, voice traffic
is guaranteed low latency for 20 percent of the 2 Mbps, and the video class is guaranteed 50 percent of
the 2 Mbps.
The remaining traffic is classified into two traffic classes. The ftp traffic class is policed at 2 Mbps and
any FTP traffic above the policing rate has the Frame Relay DE bit set to 1. The remaining traffic has
the Frame Relay DE bit set to 1.
This type of configuration is common in service providers the offer QoS-based services.

Processing Order for Actions in Hierarchical Policies

In hierarchical policies, some actions are applied starting at the top level of the hierarchy and others are
applied starting at the bottom level of the hierarchy.
For example, if the set dscp command appears at multiple layers in the hierarchy (multiple set dscp
commands can apply to the same packet), the final DSCP value for the packet is the one in the set
command at the bottom level of the hierarchy. The hierarchy is processed starting at the top and
traversing to the bottom. Packet classification also happens starting at the top and traversing to the
bottom.
For all actions other than those using set commands, the hierarchy is traversed from the bottom level of
the hierarchy to the top level. For example, all queueing actions and the police action (including when
the policer performs marking with the conform, exceed, or violate action at any level of the hierarchy)
execute from the bottom level of the hierarchy to the top level of the hierarchy.
WRED
If WRED is configured in the middle-level policy and a set action is configured for the same filter in the
bottom-level policy, WRED is based on the newly remarked value of the filter from the bottom-level
policy.
If there is a stand-alone set action as part of a policer action, the packet is marked with the set value in
the policer, because that is executed last.
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide
QC-128
class video
bandwidth percent 50
class class-default
service-policy set-frde
class ftp
police rate 2 mbps
conform-action transmit
exceed-action set fr-de 1
class class-default
set-frde 1
Configuring Hierarchical Modular QoS on Cisco ASR 9000 Series Routers
OL-23108-02