srr-queue bandwidth share - why this difference ?

Unanswered Question
Apr 8th, 2009

I am trying to understand why the following SPECIFIC share/shape settings have been applied on a 3560, I understand some of the principles involved.

Outside of Call Signalling and Bearer traffic, all other traffic is default (0)

mls qos srr-queue output dscp-map queue 1 threshold 3 46

mls qos srr-queue output dscp-map queue 2 threshold 2 24 26

mls qos srr-queue output dscp-map queue 3 threshold 3 0

mls qos srr-queue output cos-map queue 3 threshold 3 0

mls qos srr-queue output cos-map queue 1 threshold 3 5

mls qos srr-queue output cos-map queue 2 threshold 2 3

“non-voice port” (port A)

srr-queue bandwidth share 10 10 60 20

srr-queue bandwidth shape 10 0 0 0

“voice port” (port B)

srr-queue bandwidth share 1 70 25 5

srr-queue bandwidth shape 3 0 0 0

priority-queue out

mls qos trust device cisco-phone

mls qos trust cos

I understand the traffic queue mapping, I understand the priority queue on voice ports.

Why share 60% to Q3 on port A, but only 25% on port B ?

Port B shares 70% to Q2, but if the majority of traffic is in Q3, why ?

Once voice is prioritised (where applicable) why are the other Q bandwidth allocations so different between the 2 switch ports ?

Are these AutoQOS settings / default settings ? I BELIEVE that there is no issue in practice (because only Q3 traffic would congest the interface anyway). Is this true ?

I have this problem too.
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Marwan ALshawi Wed, 04/08/2009 - 14:29

Hi

Shaped or shared bandwidth weights can be assigned to a queue using the srr-queue bandwidth shape and srr-queue bandwidth share interface commands. Shaped-mode weights override shared-mode weights. Also, if shaped weights are set to 0, the queue is operating in shared mode

in your config

Queue 1 the priority queue will be serviced first but also to avoid let this queue take all other queues bandiwdth is shaped to max 30 as the amount you put in the sahpe other queue will use the remaining percent based on the share not shape as shape is 0

if helpful Rate

ajenks Thu, 04/09/2009 - 01:27

Thanks, I understand this.

My main question though is why such the difference in bandwidth allocated to Q2 and Q3 between these 2 port configs.

"non-voice port" (port A)

srr-queue bandwidth share 10 10 60 20

srr-queue bandwidth shape 10 0 0 0

“voice port” (port B)

srr-queue bandwidth share 1 70 25 5

If the majority of traffic is mapped to Q3 - why such the difference in the treatment of Q3 between the 2 port configs ?

Marwan ALshawi Thu, 04/09/2009 - 02:03

ask who configured this switch !

the idea there you can ajusted upon your requirments

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