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36xx ATM IMA network with erratic response time, need queuing?

There is erratic response times over the ATM/IMA network. I suspect the FIFO queuing is the problem.

The networks consists of ATM over T1s through IMA/nT1 adapters on 3662 and 3640s. The ATM network uses VBR-NRT PVCs with PCS/SCR/MBS stetings match the carrier switches.

Symptoms are erratic response time during periods of moderate utilization and bursts of output drops.

I suspect the queuing using FIFO(default) is hurting. I suspect a better queuing strategy would help, such as CBWFQ with LLQ. The doc I found does not apply to the 36xx IMAs.

The IOS is 12.2(8)T1. There is no voice on the network. CPU usage is 2-5%.

Questions I have include; How do I find out what the default TX-RING-LIMIT currently is? Can I implement CBWFQ similar to WFQ? Which docs cover this for the 36xx line?


Re: 36xx ATM IMA network with erratic response time, need queuin

Since there has been no response to your post, it appears to be either too complex or too rare an issue for other forum members to assist you. If you don't get a suitable response to your post, you may wish to review our resources at the online Technical Assistance Center ( or speak with a TAC engineer. You can open a TAC case online at

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