3560 'srr-queue bandwidth shape' weighting

rich_foster · ‎06-17-2010

According to some Cisco 360 R&S lab documentation I'm reading the command 'srr-queue bandwidth shape 4 4 0 0' will result in queue's 1 and 2 getting 25% of the shaped bandwidth each. I could understand this if the last two 0's were 4 but they're not, so how does the weighting allocation work?

The full syntax is as follows, although I don't think the share command has anything to do with the weighting in the shape command?

srr-queue bandwidth shape 4 4 0 0

srr-queue bandwidth share 1 1 7 3

Any help appreciated...

m.lammerse · ‎06-22-2010

Hi Richard,

the way the shape command works is that the inverse of the specified weight (i.e. 1/4) multiplied by the interface bandwidth will be what is allocated and guaranteed to the queue. So in this case it could be 1/4 * 100Mbps (assuming an FE interface), which is 25Mbps and 25%.of 100Mbps.

If a weight of 0 is specified for a queue, the queue does not participate in shaping and will share the remaining bandwidth with any other queues that also have been assigned a weight of 0.

In the example configuration you gave, the remaining bandwidth for queues 3 and 4 would be 7/(7+3) * 100Mbps and 3/(7+3)*100Mbps respectively.

HTH

Marcel

Mo'ath Al Rawashdeh · ‎06-23-2010

Hi,

Just a minor correction to Marcel's reply, the remaining bandwidth for queues' 3 & 4 would be 7/(7+3) * (100Mbps - 25Mbps - 25 Mbps) and 3/(7+3)*(100Mbps - 25Mbps - 25 Mbps) respectively.

Moath,

m.lammerse · ‎06-23-2010

Hi Moath,

in the case when both shaped queues are full, you're absolutely right. That would be a worst-case scenario for the shared queues. When there is no traffic in the shaped queues however, the shared queues should be able to go up to interface speed.

Sorry if I wasn't clear on that.

Cheers,

Marcel

rich_foster · ‎06-24-2010

Thanks for your responses - I get it now