Cisco Weighted Round Robin

So I'm trying to understand weighted round robin queues a little bit better. I understand the principle behind them, it's the configuration that confuses me. Here's an example configuration and explanation from Informit .

[code:1]!
interface GigabitEthernet1/1
no ip address
wrr-queue bandwidth 50 75
wrr-queue queue-limit 100 50
wrr-queue cos-map 1 1 0 2
wrr-queue cos-map 1 2 3
wrr-queue cos-map 2 1 4
wrr-queue cos-map 2 2 6
priority-queue cos-map 1 1 5 7
switchport
![/code:1]

Ok, the lines for wrr-queue cos-map. The first number is for "queue id" second is for "threshold id". Do these correspond to the wrr-queue bandwidth and queue-limit values, respectively? The numbers after that are for the class of service values, which I understand.

Secondly, for wrr-queue bandwidth, I'll post this quote from the Informit article that confuses me.

The weight can take any value between 1 and 255. Assign the ratio by using the following formulas:

*

— To queue 1: [weight 1 / sum(weights)]
*

— To queue 2: [weight 2 / sum(weights)]
*

— To queue n: [weight n / sum(weights)]

You must define the weight for all types of queues. These weight types do not need to be the same.

So is this how this works. Lets say for weight 1 I choose 50 and weight 2 I choose 100. Would I then divide those values by 150? e.g. 50/150 or 100/150? Would the result of that be the wrr-queue bandwidth value? This seems a bit confusing.

Finally, on to the wrr-queue queue-limit. Each weight, which I guess correlate to a queue that is tied to certain CoS values, can have a certain amount of the buffer allocated to them, which is defined by this queue-limit. Therefore, you want lower priority queues to spend more time in the buffer than delay sensitive high priority queues, correct? Therefore, the values defined by this line tell the queues how much of it's queue can be sent to the buffer -- up to 100%.

I hope I'm on the right track with my studies. If anybody has corrections or good explanations, please share.

Jeremy,

I'm looking into this issue aswell as its of high interest, I'll get back to you as soon as I have a good answer!

Cheers,

hey,
you said

Code:
!
interface GigabitEthernet1/1
no ip address
wrr-queue bandwidth 50 75
wrr-queue queue-limit 100 50
wrr-queue cos-map 1 1 0 2
wrr-queue cos-map 1 2 3
wrr-queue cos-map 2 1 4
wrr-queue cos-map 2 2 6
priority-queue cos-map 1 1 5 7
switchport
!


Ok, the lines for wrr-queue cos-map. The first number is for "queue id" second is for "threshold id". Do these correspond to the wrr-queue bandwidth and queue-limit values, respectively?

i don't think that the "queue id" is taken from the bandwith command and the "threshold" from the queue-limit. The bandwith command is for the the "weight" in the weighted queuing, and the queue-limit is for memory-boundries.

The threshold field in the cos-map (<queue-id> <threshold-id>) actually corresponds to the WRED thresholds (the random-detect command).

That makes sense! Thanks for the clarification.