Rate Limiting

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I work in a school district and was wondering if anyone a good starting point to set uplink and downlink on rate limiting?
We run a ZD 3000 with a 7982 for AP's. We are going to 1:1 next year and dont want one or two students hogging bandwith, or teachers for that matter.

Thanks
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Marty

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Posted 6 years ago

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Srini, Employee

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Under Configure > WLANs > Create/Edit your WLAN >Advanced Options > you will find the option called Rate Limiting. You can set this to moderate range so that everyone can consume bandwidth only at a specific rate.

You can set upload and download Limits to this specific WLAN which varies from 0.10Mbps to 20.0Mbps.

Hope this helps!
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RTSCTS

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Rate limiting each client increases the amount of time needed to complete data transfer (assuming the air-interface is not the bottleneck). Unless a scheduling method such as air-time fairness is used (where clients with good link quality are given a slight advantage), the result will be increased contention for the channel and more rapidly diminishing performance as the number of concurrent users increases. A "hog" will want to consume a lot of data whether rate-limited or not. How then does Ruckus recommend reducing the amount of time that hog is contending for channel access?
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Keith - Pack Leader

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This is a good point but I think dependent on how we actually implement the rate limiting. Given our focus on performance, I'd be surprised if this were the result. I'll see if we can get a developer to chime in.
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Bill Kish, Official Rep

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It is true that rate limiting can reduce overall capacity. The primary reason for this is increased contention (as mentioned) and reduced MAC-layer efficiency due to smaller aggregation sizes. Modern WiFi is extremely reliant on the 802.11n aggregation mechanism for achieving high MAC-layer efficiency and anything that reduces aggregation sizes such as rate limiting can negatively impact overall capacity. Ruckus AP's mitigate this effect through the use of larger rate limiting buffers (essentially enforcing the specified rate over a longer average time interval) to allow the bursting that is essential to maximizing aggregation and MAC-layer efficiency. Our rate limiting and airtime fairness scheduler effectively give a bandwidth hog less frequent but longer access to the medium which results in reduced contention and higher efficiency. The downside is somewhat longer latency if rate limiting but most data applications don't notice it.
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Keith - Pack Leader

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This is a great conversation that's separate from the main topic, so I created a new topic to continue the discussion. Please reference the new topic here: Effect of rate-limiting on channel efficiency
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Brian Funk

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r500 manual
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Marty

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I know how to use it, just wondering if any other person has experienced a good setting that they use with their employee's, or in my case, students?
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Bill Kish, Official Rep

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Official Response
It turns out that Ruckus AP's airtime fairness scheduling algorithm is pretty good at preventing a user from monopolizing the wireless access capacity, so rate limiting is really best used to prevent a user from monopolizing the internet backhaul capacity.

As such, the optimal value for rate limiting will depend on a number of factors such as the available internet capacity and expected applications. As a default I would start at something like 25-50% of the internet backhaul capacity, just to preclude a bandwidth hog from monopolizing the backhaul, and go down from there if required. In general I think it is better to err a bit on the high side.
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Marty

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Thank you for you help

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