3750 queuing, how to decide on which queue/threshold to use

[aacole]

I am working on a QoS design which I hope to test at some point, but at this stage its from the books.

My question is how to decide which queue and threshold to use for video traffic, then lower priority traffic

I understand the shaping and sharing commands, its the queuing and threshold bit I'm not clear on.

The plan is to use the priority-queue for EF marked voice, this will be policed on ingress to provide an upper limit to EF traffic levels, then my second priority traffic will be video. Which queue will get serviced first once the priority queue is empty, and how do I decide which threshold to allocate my video traffic to?

The documention is not at all clear, I want to prioritse my traffic in the following order:

1 voice, use the priority queue

2 video, this to get serviced ahead of data, after voice.

3 interactive data

4 Bulk data

5 Best effort

The port configuration will be:

priority-queue out

srr-queue bandwidth shape 1 0 0 0

srr-queue bandwidth share 1 70 25 5

So Q1 settings are ignored due to priority queue. Q2 gets 70%, Q3 25% etc.

Is it as simple as putting video into Q2 T1, then interactive data into Q2 T2, will Q2T1 get a higher priority over Q2 T2 once the PQ is serviced?

[Joseph W. Doherty]

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Posting

All traffic in the same physical queue gets same dequeuing scheduling priority, as that's tied to the queue.  What the thresholds do, is allow some traffic to be dropped before other traffic as the queue fills.

Say, for example, both your Interactive Data and Bulk Data were sent to the same queue.  You could configure the queue that once 50% is reached, all new Bulk Data is dropped until the queue depth goes back down below 50%.  Whatever's actually in the Bulk Data and Interactive Data queue would be dequeued, relative to other queues, regardless of the actual mix of packets in that queue.

PS:

Oh, and yes, you prioritize by bandwidth allocations per queue relative to other queues.

[aacole]

Thanks for reply, have not yet had a chance to put this into practice. After looking at this again I have found information that shows my settings are wrong, as the bandwidth applied to the queue is the inverse of the number entered.

So if that is correct for srr-queue bandwidth share 1 70 25 5 Q2 gets 1.4%, Q3 gets 4% and Q4 gets 20%, would you agree?

Andy

[Joseph W. Doherty]

Disclaimer

The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.

Posting

No, you're were correct 1st time, but perhaps not for the reason you thought.  Share values are weights, not percentages.

Given:

The port configuration will be:

priority-queue out

srr-queue bandwidth shape 1 0 0 0

srr-queue bandwidth share 1 70 25 5

Queue 1 is PQ and can take all the bandwidth.  Whatever isn't used is available to the other queues and they are "entitled" to:

70 / (70 + 25 + 5) = 70%

25 / (70 + 25 + 5) = 25%

5 / (70 + 25 + 5) = 5%

The weights match the end percentage because the divisor is 100.

PS:

Inverse values, for percentages, applies to "shape" values.

[aacole]

Hi Joseph,

Thanks for that, managed to get it all working at the weekend, now just waiting on feedback from customer.

Andy

From: JosephDoherty

Sent: 06 April 2012 18:10

To: Andy Cole

Subject: - Re: 3750 queuing, how to decide on which queue/threshold to use

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Re: 3750 queuing, how to decide on which queue/threshold to use

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