BSSID counters does not reflect true data volumes for Cisco AP C9120AX

[Anders Hedlund]

We are pushing traffic using a packet generator on a client at a rate of 10Mbit/s via a Cisco AP C9120AXI-E.
Using the following command we can fetch the BSSID counters form the WLC9800.
show wireless stats ap name AP8C1E.8025.7D7C dot11 5ghz slot 1 wlan-id 5 statistics

In one test, we run the packet generator for 164 seconds, so all in all we pushed 164*10Mbit/8 = 205Mbytes
>>> 164*10*10**6/(8*10**6)
205.0

At the same time, we monitor the “RX Statistics” field “Data Bytes”.
Before:
851179521
After:
867610603
>>> (867610603 - 851179521)/(10**6)
16.431082
They show only 16.4Mbyte!!

We have also tested over a long time to get rid of any ramping/filtering effects, but each test gives different results, and they are always much lower than the true traffic volumes.
As a sidenote we have tested other counters that counts number of packets over time, and they match the number of packets from the packet generator.

Anyone having experience with the BSSID counters? If we can get this up and running, they seem like the perfect data source for checking RF performance.

Thanks, Anders

[marce1000]

 - I would suppose that https://bst.cloudapps.cisco.com/bugsearch/bug/CSCvu29416 , is not directly related to your problem but I would pay attention to software version being used and the Fixed Releases in the bug report (anyway). Using  later releases might help , if applicable. 

 M.

[Rich R]

Which leads to the question - what version were you testing with? (should always be specified because it's relevant to features and bugs)

[Anders Hedlund]

Hi and thanks for the replies, now I have the version ready below:

<version>17</version>
<release>3</release>
<maint>6</maint>
<build>76</build>

/Anders

[Rich R]

So the bug @marce1000 mentioned should be fixed in 17.3.6 but there are others like:
https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwe25897
https://bst.cloudapps.cisco.com/bugsearch/bug/CSCvk72676
Probably best to open a TAC case and they'll either match it with an existing bug or open a new one for you.

[Anders Hedlund]

We have just verified that the counters and the measurement setup work fine using another Cisco AP model (C9124AXE-E (note 9124) with build 17.3.6.76 (same as the 9120 that is not working)).
Always great to know we have done a correct measurement setup and have the scripts and mathematics in place.
We plan to do more experiments, and we have other versions of the 9210 also, to exclude hardware, CPU load, memory issues etc.

[Anders Hedlund]

We have done more testing here, first we realize that the problem on release 17.3.6.76 occurs on the counters related to the uplink (rx-bytes-data etc) (our main application pushes traffic from a client to the network). If we push the same controlled stream with fixed rate in the other direction (from a server to the client), the counters related to the tx part (tx-bytes-data) are updated correctly.

Next test we did was done on an experimental WLC 9800-CL where we could push newer firmware (17.10.0.181) to the 9210, and now the rx-bytes-data counters are updated correctly.
So we’ll await an update of our production WLC (9800 L-F) that can supply newer firmware than 17.3.6.76 for the 9210.

[Rich R]

Thanks for the update @Anders Hedlund - good to know it's fixed in latest IOS.