Wireless Access

Contributor I

Setting Transmit Rate on SSID doesn't appear to change anything

We want to limit the connection speed (not bandwidth) of users in our Warehouse to a flat 6mbps up/down on 2.5 and 5Ghz. This isn't to limit bandwidth, but to stop the radios on the tablets that the staff use from changing rates and causing instability.


We're using the Zones feature to setup an SSID that is broadcast only on our Warehouse APs.


Transmit Rates for 2.4/5 have been set to 6/6 - but this doesn't appear to have had an effect at all.


Is there a way to verify the transmit rate for the new SSID has been correctly configured in the cli maybe? Or do these rate settings need to be configured anywhere else? 

MVP Guru

Re: Setting Transmit Rate on SSID doesn't appear to change anything

Is this on a Controller or IAP? The supported data rates will be shown in the respective CLI output. You can also during the meantime verify the supported transmit rates by looking at the beacon frame using a protocol analyzer

If my post addresses your query, give kudos:)
Guru Elite

Re: Setting Transmit Rate on SSID doesn't appear to change anything

Changing the rates will not eliminate the issue you are seeing.  If rates on devices are changing rapidly, it could be due to co-channel interference or reflections off objects in an environment.  You might want to evaluate how many access points a client can see in an area with the issue to determine if you need to reduce the maximum transmit power of access points.

*Answers and views expressed by me on this forum are my own and not necessarily the position of Aruba Networks or Hewlett Packard Enterprise.*
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Contributor I

Re: Setting Transmit Rate on SSID doesn't appear to change anything

So I've configured a new SSID in the group, with the zone of Warehouse.


And on one IAP in the cluster I've configured it's zone to be Warehouse.


The SSID is being broadcast from that IAP as expected (along with the other SSIDs on our network) 

In Airwave I've set the Transmit Rates min/max to 6/6mpbs for the Warehouse network.


When I connect to this network though it doesn't appear to be limited to 6mpbs in either direction. 


However when I set the Bandwidth Limit - then I see the expected speeds. Do these setiings need to be set together?


Re: Setting Transmit Rate on SSID doesn't appear to change anything

If you want to limit the tcp/ip traffic of the devices, you should be using bandwidth contracts. There are a number of more complex things happening with PHY rates that make it very difficult to control TCP/IP bandwidth using radio rates alone - some examples area) PHY rate is not the same as data rate, a 6Mbps radio frame cannot transport 6Mbps of TCP/IP traffic as there are overheads involved at various layers. For TCP traffic using iperf testing, you may see something like 75 to 80% of the PHY rate appearing as the traffic rate - this is assuming it uses a single PHY rate, which it often won'tb) The rate you are changing is the a (or g) tx-rate, there are also HT and VHT rates that can be used by traffic that are not so easily (if at all) able to be disabledc) the radio rate itself doesnt take into account any nature of the medium (half duplex) and contention etc. Suppose I could hypothethically set a single tx rate of 300Mbps (of which under near ideal conditions might give you a traffic rate of some 220 Mbps) as soon as that network has traffic or other impairments the effective throughput will drop so the number is kind of meaninglessTL;DR; controller TCP/IP traffic rates with BW contracts not radio rates. Radio rates are more about optimising behaviors of the radio layer with respect to your deployment density (e.g. the more APs present the more you would generally try (see note) to raise up radio rates)Note: this is a generic statement, subject to various other things, I am just stating it here for illustration - your network may or may not benefit from thathth-jeff

Contributor I

Re: Setting Transmit Rate on SSID doesn't appear to change anything

Thank you for your detailed reply:


I don't want to necessarily limit bandwidth - the idea is to set the same min/max data rate (physical) so the clients won't be changing data rates all the time. 6/6mbps for instance.


This particular installation is inside a Warehouse, we are getting complaints from the Warehouse staff regarding disconnections - speed is not a priority at all. 1Mbps would be absoloutely fine. 


My problem is setting the Transmit Rate to 6mpbs doesn't appear to have any effect - I'm seeing clients transfer data at 40mbps, and therefore the data rate of the radios must not be limited to 6mpbs.


Re: Setting Transmit Rate on SSID doesn't appear to change anything

tx-rate set is largely ignored by anything that is a 11n or higher client - which will more generally use HT and VHT rates for traffic. Unless you have really old clients, those rates are is more often utilised by management & control traffic. Please ensure that if you are raising the tx-rates that the basic rates are raised too to match the lowest one or two configured tx rates.


This old post kind of goes into the various options



but, in 802.11ac it's not possible to slice out the low VHT rates (if i recall correctly right now), so attempts to corral the users to a tight range of tx rates are generally futile (and may not serve any purpose, see next point)


To your latter comment about disconnections - best to try and narrow it down before changing things - is it ARM, is it beacons is it RF etc.


What band are the clients on and what kind of radio do they have, would be a starting point. Also, what is the AP density and what is the typical tx power being used by the APs ? What is the current setting of the rates ?


To speak generally about problems that often crop up in warehouses are things like bad/uneven tx power, 2.4ghz interference, frequent channel changes (for various reasons).


We can debate it a bit more in here, or, you might get some benefit to kick off another thread titled more around warehouse problems to see what the community has to say.



Contributor I

Re: Setting Transmit Rate on SSID doesn't appear to change anything

Thanks for you help Jeff - I will work on answering some of those basic questions before posting another thread, cheers.

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