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    Example: Simple Shared Shaping for ATM VPs

    In the example shown in Figure 1, VP 1 is shaped to a shared rate of 5 Mbps. The shared shaper requires that voice and video traffic be carried in queues associated with the logical interface, which in this scenario is the VP. VP-level queuing does not guarantee fairness to the voice and video traffic for each VC, but fairness is not a major issue because admission control guarantees that the voice and video queues do not become congested.

    This example assumes the same traffic class and traffic-class group configurations that are used in Example: Simple Shared Shaping for ATM VCs.

    Figure 1: VP Shared Shaping

    VP Shared Shaping

    The following set of commands configures the shared shaper in Figure 1.

    host1(config)#scheduler-profile 2mbps host1(config-scheduler-profile)#shaping-rate 2000000 host1(config-scheduler-profile)#exit host1(config)#scheduler-profile 400kbps host1(config-scheduler-profile)#shaping-rate 400000 (config-scheduler-profile)#exit host1(config)#scheduler-profile shared-5mbps host1(config-scheduler-profile)#shared-shaping-rate 5000000 simple host1(config-scheduler-profile)#exit
    host1(config)#qos-profile vp-subscriber1 host1(config-qos-profile)#atm-vp node scheduler-profile shared-5mbps host1(config-qos-profile)#atm-vp node group AF host1(config-qos-profile)#atm-vp node group EF host1(config-qos-profile)#atm-vc node host1(config-qos-profile)#atm-vc queue traffic-class best-effort scheduler-profile default host1(config-qos-profile)#atm-vp queue traffic-class video scheduler-profile 2mbps host1(config-qos-profile)#atm-vp queue traffic-class voice scheduler-profile 400kbps host1(config-qos-profile)#exit

    In this example, the best-effort scheduler node for the VP is shaped to a shared rate of 5 Mbps. The EF and AF queues for the VP share the 5 Mbps with the best-effort traffic. The EF queue has first claim on the shared 5 Mbps, but only up to its individual shaping rate of 400 Kbps. The AF queue claims up to the next 2 Mbps. The VC-level best-effort queues obtain whatever bandwidth remains of the 5 Mbps after the AF traffic and EF traffic have made their claims. This QoS profile is appropriate for low-CDV mode. If the provider configures a shapeless VP tunnel in the SAR, QoS sets the SAR shaper for the VP to match the 5-Mbps shared-shaping rate, and the CDV is bounded for the VP tunnel.

    Published: 2014-08-11