QoS and QoS Policies
84
Quality of Service Guide
3HE 11014 AAAC TQZZA Edition: 01
The SAPs without an aggregate rate limit, which are called unshaped SAPs, can be
scheduled using either 4-priority or 16-priority mode as one of the following:
• unshaped SAPs bound to a 4-priority scheduler
• unshaped SAPs bound to a 16-priority scheduler
The arbitration of access ingress traffic leaving the 4-priority and 16-priority
schedulers and continuing towards the fabric is described in the following section.
3.2.4.1 Access Ingress Per-SAP Shapers Arbitration
The 7705 SAR provides per-SAP aggregate shapers for access ingress SAPs. With
this feature, both shaped and unshaped SAPs can coexist on the same adapter card.
When switching traffic from shaped and unshaped SAPs to the fabric, arbitration is
required.
Figure 18 shows how the 7705 SAR arbitrates traffic to the fabric between 4-priority
unshaped SAPs, and 16-priority shaped and unshaped SAPs.
All SAPs support configurable CIR and PIR rates on a per-CoS queue basis
(per-queue level). In addition, each 16-priority SAP has its own configurable per-SAP
aggregate CIR and PIR rates that operate one level above the per-queue rates.
To allow the 4-priority unshaped SAPs to compete for fabric bandwidth with the
aggregate CIR rates of the shaped SAPs, the 4-priority unshaped SAPs (as a group)
have their own configurable unshaped SAP aggregate CIR rate, which is configured
on the 7705 SAR-8 and 7705 SAR-18 under the config>qos>fabric-profile
aggregate-mode context using the unshaped-sap-cir parameter. On the
7705 SAR-M, 7705 SAR-H, 7705 SAR-Hc, 7705 SAR-A, 7705 SAR-Ax,
7705 SAR-W, and 7705 SAR-Wx, the CIR rate is configured in the
config>system>qos>access-ingress-aggregate-rate context.
The configured CIR and PIR for the 16-priority shaped SAPs dictates committed and
uncommitted fabric bandwidth for each of these SAPs. Configuring the
unshaped-sap-cir parameter for the group (aggregate) of 4-priority unshaped SAPs
ensures that the unshaped SAPs will compete for fabric bandwidth with the
aggregate CIR rate of the shaped SAPs. Otherwise, the unshaped SAPs would only
be able to send traffic into the fabric after the aggregate CIR rates of all the shaped
SAPs were serviced. The 16-priority unshaped SAPs are serviced as if they are
non-conforming traffic for 16-priority shaped SAPs.
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