Hierarchical QoS (HQoS) corresponds to scheduling bandwidth distribution to policers, queues and schedulers and is applied using scheduler policies at ingress and egress of the subscriber profile for a subscriber, and at egress in the SLA profile for a host, together with a port scheduler at both the port and Vport level.
Each scheduler policy can contain up to three tiers of schedulers with lower level schedulers being able to parent to higher level schedulers in the same scheduler policy.
Policers and queues can parent to any scheduler in their related scheduler policy hierarchy (except Vport at egress) and also at the egress to a port scheduler.
Schedulers can parent to any higher level scheduler in their related scheduler policy hierarchy and, at the egress to a port scheduler configured within the port or Vport. When an egress port scheduler is used, an aggregate rate limit can be applied at the subscriber profile and Vport levels instead of using a scheduler. To extend the hierarchy further at egress, a tier 1 scheduler within a scheduler policy can parent to any scheduler in a scheduler policy at a higher level.
The scheduling levels are composed of:
ingress and egress queues
egress policers
egress SLA-profile schedulers
ingress and egress subscriber profile schedulers
egress Vport schedulers
port schedulers
The ingress hierarchical parenting relationship options are shown in Figure: Ingress scheduling hierarchy options.
The egress hierarchical parenting relationship options are shown in Figure: Egress scheduling hierarchy options. Not all combinations can be configured concurrently, and some uses of port parent could be equally achieved using a scheduler parent and a child parent-location.
The parent command is used to specify the name of the parent scheduler when parenting a queue or scheduler, together with the level/cir-level and weight/cir-weight at which to connect.
config>qos>sap-ingress>queue# parent
- parent scheduler-name [weight weight] [level level]
[cir-weight cir-weight] [cir-level cir-level]
config>qos>sap-egress>queue# parent
- parent scheduler-name [weight weight] [level level]
[cir-weight cir-weight] [cir-level cir-level]
config>qos>scheduler-policy>tier>scheduler# parent
- parent scheduler-name [weight weight] [level level]
[cir-weight cir-weight] [cir-level cir-level]
The location of the parent scheduler (in which applied scheduler policy it exists) for a policer or queue defaults to a scheduler in the subscriber ingress or egress scheduler policy. Parents of schedulers themselves must be explicitly configured and by default must be within the same scheduler policy.
At egress, the scheduler parenting relationship is determined using the parent-location command:
By default, egress queues parent to any scheduler in subscriber egress scheduler policy.
config>qos>sap-egress# parent-location default
Egress queues can parent to any scheduler within the scheduler policy applied to the egress of an SLA profile (this is not supported for policers managed by HQoS).
config>qos>sap-egress# parent-location sla
By default, a tier 1 scheduler in the scheduler policy is not allowed to be parented to another scheduler.
config>qos>scheduler-policy>tier# parent-location none
A tier 1 scheduler in the scheduler policy applied to the egress of an SLA profile can parent to a scheduler applied to the egress of a subscriber profile.
config>qos>scheduler-policy>tier# parent-location sub
A tier 1 scheduler in the scheduler policy applied to the egress of a subscriber profile can parent to a scheduler applied to the egress of a Vport.
config>qos>scheduler-policy>tier# parent-location vport
The configuration of a parent-location and frame-based accounting in a scheduler policy is mutually exclusive to ensure consistency between the different scheduling levels.
Note that the parent-location command is supported only on Ethernet interfaces. It is not supported for ESM over MPLS pseudowires.
Both egress queues and egress schedulers can port parent using directly to different levels/cir-levels, with different weights/cir weights, to a port egress port scheduler. Egress schedulers can also port parent directly to different levels/cir-levels, with different weights/cir weights, to a Vport egress port scheduler.