Quality of Service Guide QoS and QoS Policies
Edition: 01 3HE 11014 AAAC TQZZA 119
After the queuing, an aggregate queue-type and profile scheduling takes place in the
following order:
1. Expedited in-profile traffic
2. Best Effort in-profile traffic
3. Expedited out-of-profile traffic
4. Best Effort out-of-profile traffic
Once the traffic is scheduled using the aggregate queue-type and profile schedulers,
the per-port shapers shape the traffic at a sub-rate (that is, at the configured/shaped
port rate). Per-port shapers ensure that a sub-rate is met and attainable at all times.
3.6.2 Access Egress Per-SAP Aggregate Shapers
(Access Egress H-QoS)
Per-SAP aggregate shapers in the access egress direction operate in a similar
fashion to aggregate shapers for access ingress, except that egress traffic goes
through the schedulers to the egress port shaper instead of through the schedulers
to the fabric port as in the access ingress case. For information on how access
egress and access ingress per-SAP shaping is similar, see Access Ingress Per-SAP
Aggregate Shapers (Access Ingress H-QoS). For general information on per-SAP
shapers, see Per-SAP Aggregate Shapers (H-QoS) On Gen-2 Hardware.
The arbitration of access egress traffic from the per-SAP aggregate shapers to the
schedulers is described in the following section.
3.6.2.1 Access Egress Per-SAP Shapers Arbitration
The arbitration of traffic from 4-priority and 16-priority schedulers towards an access
egress port is achieved by configuring a committed aggregate rate limit for the
aggregate of all the 4-priority unshaped SAPs. By configuring the 4-priority unshaped
SAPs committed aggregate rate, the arbitration between the 16-priority shaped
SAPs, 16-priority unshaped SAPs, and 4-priority unshaped SAPs is handled in the
following priority order:
• committed traffic: 16-priority per-SAP agg-rate-limit committed for shaped
SAPs and 4-priority aggregate committed rate for all the unshaped SAPs
• uncommitted traffic: 16-priority per-SAP agg-rate-limit uncommitted for shaped
and unshaped SAPs and 4-priority aggregate uncommitted rate for all the
unshaped SAPs
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