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: Access Ingress per-SAP Arbitration to Fabric 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 Shelf V2 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, 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.
The aggregate fabric shaper (Figure: Access Ingress per-SAP Arbitration to Fabric ) performs round-robin selection between the 16-priority SAPs (shaped and unshaped) and the 4-priority unshaped SAP aggregate until:
the aggregate fabric shaper rate is exceeded
the conforming (CIR) traffic for every 16-priority SAP and the 4-priority unshaped SAP aggregate is exceeded
the non-conforming traffic for every 16-priority SAP and the 4-priority unshaped SAP aggregate is completed, provided that the aggregate PIR rate is not exceeded