2504 running on 8.5.151.0 - bandwidth issues

[danailpetrov]

Hi guys,

I am having some weird problems with my 2504 controller running on 8.5.151.0 

I noticed today that I am unable to achieve more than 30-32Mbps on an individual device. It's like there is a hard-cap that doesn't let the device getting more bandwidth. 

I have played alot, trying to tweak different QoS settings, but apparently 2500 is very limited in configuration of the bandwidth rates, burts and traffic profiles. I was unable to find a way to completely disable the qos for an SSID and just let it be on "best effort". 

My questions are: 

* are there any built-in, default policers for different classes and if so - what are the values? 

* Is there anyway possible I can completely switch off that behaviour (preferably on a per SSID basis?)

* Is that an 8.5.151.x problem because I don't recall having this problem on older versions

[Scott Fella]

I have a 2504 along with other controller that I run at home. With the 2504, I never. Had any issues with what you are seeing. I also do not enable every feature that is available and many others here also do not. Very hard to tell you what might be wrong without looking at your controller. This is why sometimes we suggest opening up a TAC case, because they will look at. Your setup. I’m guessing you don’t have support, but what I can say for tinkering with controllers for many years and that this is a home setup. Start from scratch and don’t add anything extra, don’t go an look at the best practice and enable/fix everything, just do the basics. Then on the plan, always test with an open SSID and then use that to compare when you start locking things down. What we are assuming is that your devices have no issues, that this happens on all devices and that. You network setup is also fine.

[patoberli]

Sorry didn't anymore remember that it happens with all.
The only WMM settings that should be configured is under WLANS - select SSID - QoS - WMM Policy set to allowed. The other two options under WMM not selected. QoS itself can be set to Gold, but should not make any difference with one SSID.
Everything else under QoS set to None or Disabled.
Do you have a managed switch where your WLC is attached to? If yes, are the interface counters clean (no errors)?

[TsvetanVladimirov81607]

Hey there,

Go to Wireless- Global Configuration and set the TCP MSS to 1250 is one suggestion from my side. Might be having issues with fragmentation which can start increasing the latency. Although strange.
Also get two devices on the wired network in the same VLAN, as the one that you have issues with and do an IPerf test. Make sure to verify that there isn't an issue with the DS.
Scott also suggested the use of Flexconnect local switching. If the WLC has issues this will bypass it for sure. (It will be a good idea to give it a test).

Long ago there was a bug related with those 1850 APs that they were having low throughput, not sure if you are not hitting the same thing.

[danailpetrov]

Hi mate and thanks for your response. 

I don't think the MSS is playing any significant role here as it is within the local LAN where no overhead is added to the IP header. Furthermore, the tests observed were conducted for both - TCP and UDP and the results are not much better (the only difference kicks in when latency increases during the bandwidth throughput and as a result due to the nature of TCP (being hit by RTT))  

Wired devices within the same VLAN perform as expected at line rate (~120MBs/~1Gbps). 

I think I have established another problem where my both MACs perform differently, which may come down to a driver issue, but other PCs on the network also cannot achieve the bandwidth I was able to get in the past. 

I started reading this guide and will try to follow it as close as possible & will share the results back.

Thanks

[TsvetanVladimirov81607]

Boy, you got your hands full there. 

Check this best practice guide. Might have some useful information inside.

https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-6/b_Cisco_Wireless_LAN_Controller_Configuration_Best_Practices.html#concept_9C3806DC6959422B8C536EEBF3A66D59

Couple of other stuff coming to my mind are:

- Check what is the Current TxRateSet for the user when you perform the tests. See if the clients are just not able to jump on higher data rate (that would mean that there are retransmissions).

- See if you have Mu-Mimo enabled on the SSID (if yes - disable it, if no - enable it). There was a bug that was supposed to be fixed on your version with clients that have Mimo in power saving mode - limiting their throughput on 802.11ac. But hey, doesn't hurt to try it.

- Test on 2.4Ghz? See what rates and speeds can you get if you are on 802.11b/g/n.

- Verify the "Interoperability with Other Clients" section in the Release Notes for 8.5.151.0 version. There were macs there with operation version that are expected to have issues with this firmware (which would mean that a client update is required).

Btw, nice guide with the MACs :) I would definitely have it in mind for future references thanks!

Looking forward to hear from you if this was helpful.