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Cisco Bug: CSCtb79351 - Egress QoS on ChOC12 SPA drops priority traffic incorrectly

Last Modified

Jan 28, 2017

Products (1)

  • Cisco 12000 Series Routers

Known Affected Releases

3.8.2.8i.FWDG

Description (partial)

Symptom:

Egress QoS on the ChOC12 SPA, configured with multilink PPP, in a SIP-601, in a 12000 series chassis may not correctly drop traffic when an interface is oversubscribed. As an example, in a multilink bundle with 2 T1s is configured on the spa. The cumulative bandwidth of the interface is ~3.088 Mbps. 2 traffic streams are sent out of the spa. 

1 high priority stream - 2.4 Mbps 
1 low priority stream - 2.4 Mbps 

The expectation is all 2.4 Mbps hi prio traffic should go through and about 0.6 Mbps of low priority traffic should pass.

But we see hi priority - 1.6 Mbps and low priority - 1.6 Mbps. This issue is not seen on a regular T1 serial interface on the same SPA. 

This issue is also seen on Viking.
Conditions:

Interface oversubscription.
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