We’re looking at moving our QoS logic from the routers to the AP’s. I’m assuming that the AP takes into account how many slots are actually being used at any given moment when it considers whether to allow bursting. It’s my thinking that the AP only allows throughput to burst above the sustained rate if excess slots are available after satisfying any current demand for each SM’s sustained rate. Is that true or does the AP always allow bursting even if there’s no excess bandwidth? If it is true, does the AP take into account available slots or just throughput.
The reason I think the bandwidth management would be better at the AP is because it knows the mix of current throughput demands at 1X/2X at any given moment. On the router, all I can do is say the AP is capable of, let’s say 8Mbps down. The router will only allow bursting above the base rate if less than 8Mbps of base rate throughput is being used at that moment. Of course, the 8Mbps is just a guess. I have no idea what the actual maximum throughput at any given moment is because some SM’s will be doing 1X and others will be doing 2X. If the AP allows bursting even when the sustained rates are not being satisfied or it doesn’t look at actual slots available, I may as well leave the bandwidth management logic at the router.
Are you using BAM/Prism? If not you need to set the sustained and burst speeds in each SM and set the AP to configuration source: SM.
The AP does not consider slots or throughput when figuring out burst. It allows an SM to transmit at maximum possible speed until the burst bucket is empty. You set the size of the burst bucket in the SM QOS page. So if you set it to 40000 kb then the SM can transmit as maximum speed until it has sent 5MB of data then it gets throttled back down to the sustained speed. Read the following for a more detailed description:
http://en.wikipedia.org/wiki/Token_bucket
Is the SM is allowed to burst even if the AP is not able to currently satisfy all the committed information rates at the moment? For example, let’s say I three SM’s with a downlink CIR of 4 Mbps and they’re all trying to move 4 Mbps. Will the AP still allow an SM that has a downlink CIR of 0 to burst at full speed until the burst buffer is used up?