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Upgrade from 7.0.220.0 to 7.2.103.0 - Terrible client performance, high latency on 7500 Flex Controller (WLC)

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Introduction

 

Client performance on Cisco 7500 Flex controller with version 7.0.220.0  work fine but high latency on code 7.2.103.0.

 

 

Scenario

 

After upgrading, ping times from clients has gone from ~10ms to ~2500ms. I have a Cisco 7500 Flex controller, when running controller code version 7.0.220.0 client performance was as expected. When using code 7.2.103.0 performance is terrible. I have tried upgrade to 7.2.103.0 and clean configuration (reset) with 7.2.103.0 with the same results.

 

I have tested using 3502i APs with the signal metrics (from AP) reported by the clients (all testing close to these figures):

Signal Strength   : -48 dBm

Signal to Noise   : 49 dB

 

AP's are in HREAP/Flex mode. The WLANs use HREAP/FlexConnect local switching. I have tested WLAN's with WPA2-PSK and 802.1x/WPA2 with the same results. I have

 

Observation

 

Several clients\operating systems , laptops, ipads, iphone have been tested and all experience consistently poor ping latency performance on both 2.4Ghz and 5 Ghz when using controller code 7.2.103.0.

 

When it is switched between 7.0.220.0 and 7.2.103.0 the results are consistent; good performance on 7.0.220.0 and terrible performance on 7.2.103.0. We would like to use 7.2.103.0 for its enhanced FlexConnect features.

 

 

Solution

 

Here is the bug what we are hitting and here is the workaround:-

 

 

 

 

High latency with Wireless N clients on 7500 WLC running 7.2 code

Symptom:

 

AP3500 performance for 802.11n clients decreasing when connected to  WLC 7500. Other WLC platforms are not affected.

 

 

Workaround:

 

Run the following commands to disable AMPDU scheduler

 

config 802.11b 11nSupport a-mpdu tx scheduler disable
config 802.11a 11nSupport a-mpdu tx scheduler disable

 

 

Reference

 

 

This document was generated from the following discussion: Upgrade from 7.0.220.0 to 7.2.103.0 - Terrible client performance

 

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