LLQ with RED over Ethernet

Unanswered Question
Apr 7th, 2008

Just been going through QoS and labbing a few things and have come up with a problem.

When QoS is configured on a service provider ethernet link for instance a 4Mbps symmetric, queuing doesn't seem to work correctly in that most of the congestion control and avoidance mechanisms are based on the depth of the hardware queue. The question is, how to make a 100 base TX link act like a much smaller link in terms of RED and minimum bandwidth allocations. I have set the bandwidth statement however I am constantly seeing the used bandwidth exceeding that amount during testing and upon inspection the queues are showing little or no activity.

I have this problem too.
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Joseph W. Doherty Mon, 04/07/2008 - 08:32

To have QoS active on a physical link that has more bandwidth then the end-to-end path provides, you often need a shaper.

e.g. (CBWFQ pseudo config)

service-policy aShaperParent

class class-default

shape average 4Mbps

policy aQOS_Child

service-policy aQOS_Child

class class-default

random-detect

interface fastethernet 0

service-policy aShaperParent

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