QoS and QoS Policies
82
Quality of Service Guide
3HE 11014 AAAC TQZZA Edition: 01
3.2.4 Access Ingress Per-SAP Aggregate Shapers
(Access Ingress H-QoS)
On the 7705 SAR, H-QoS adds second-tier (or second-level), per-SAP aggregate
shapers. As shown in Figure 17, traffic ingresses at an Ethernet SAP and is classified
and mapped to up to eight different CoS queues on a per-ingress SAP basis. The
aggregate rate CIR and PIR values are then used to shape the traffic. The
conforming loop (aggregate CIR loop) schedules the packets out of the eight CoS
queues in strict priority manner (queue priority CIRs followed by queue priority PIRs).
If the aggregate CIR is crossed at any time during the scheduling operation,
regardless of the per-queue CIR/PIR configuration, then the aggregate conforming
loop for the SAP ends and the aggregate non-conforming loop begins. The
aggregate non-conforming loop schedules the packets out of the eight CoS queues
in strict priority manner. SAPs sending traffic to the 4-priority scheduler do not have
a second-tier per-SAP aggregate shaper unless traffic arbitration is desired, in which
case an aggregate CIR for all the 4-priority SAPs can be configured (see Access
Ingress Per-SAP Shapers Arbitration). See Per-SAP Aggregate Shapers (H-QoS)
On Gen-2 Hardware for general information.
The aggregate rate limit for the per-SAP aggregate shaper is configured in the
service context, using the sap>ingress>agg-rate-limit or sap>egress>agg-rate-
limit command.
For per-SAP aggregate shaping on Gen-2 adapter cards, the SAP must be
scheduled using a 16-priority scheduler.
Note: The default setting for scheduler-mode is 4-priority on Gen-2 adapter cards and
platforms. The user must toggle the scheduling mode to 16-priority for a given SAP before
SAP aggregate shaper rates (agg-rate-limit) can be configured. Before changing the
scheduling mode, the SAP must be shut down.
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