MSM760 - performance issue with Guest VSC

[svhelden]

We have an MSM760 (5.5.4.0) with ca. 90 APs and multiple VSCs. Most VSCs are connected to the internal LAN and are performing fine.

The Guest VSC - which is connected to an ADSL router via the Internet port - is performing poorly though. When we connect a computer to the same switch, download rates are between 12 and 15 mbit/s. When we connect via WiFi, download rate is something between 0.5 and 2 mbit/s. It can't be the wireless connection itself because download from an internal source (via another VSC) is fast. The wireless connection is established with 54 mbit/s. I checked that there are no bandwidth limits applied in the Controller and VSC configuration. We also ruled out LAN issues.

It seems that the MSM760 somehow limits the traffic, or ist just not fast enough to handle it. We have the impression - but can't definitely proof it - that it worked better originally, and then the issue started some months ago.

Is performance a known issue? Can it be related to too many APs, user accounts, connected users, etc.? Or are there any settings that I haven't found yet?