Sunday, May 29, 2016

WiFi signal problem that's well beyond the norm.

I’m completely stuck on a wireless problem.   


What at first glance appears like slow wifi is actually much more insidious — while at times I can get full bandwidth, it will then drop dramatically, going from a solid set of speeds between 60-90 Mbps download to levels that are measured instead in Kbps, from 20 to 50 Kpbs.   At first, I noticed this only on my Macbook.  However, intensive testing revealed that I could see the same problem on other machines -- my Windows laptop and my iPhone.  

My wireless network is provided by a set of three Apple Airport units of various ages.  Coverage is fantastic, and the units generally load balance across the three level house.    I can replicate this problem regardless of which AirPort / Access Point the endpoint is connected to.    From Airport Utility:


I have two primary production wireless networks, evolvetech_extreme and evolvetech_extreme 5Ghz.     Using iStumbler to show the list of networks:


Note there is a set of "_uk" networks that are not at all linked to the same network, living outside the firewall.  I can replicate the problem on BOTH the 2.4 Ghz and the 5Ghz networks.     This seems to tell me that I don't have significant channel overlap nor signal problems.   I've also done some testing with Android's WiFi Analyzer and I can't find a problem.

These speed tests were taken within 5 minutes of each other:

From a Macbook:


From an iPhone:


From a Windows laptop:




In this example, I'm seeing the problem on the Windows machine but not the other two.  

During this, network probes on the firewall show me that the overall bandwidth (which is 75/75 Mbps), is running without significant load:



So far, I can tell that:

- The endpoint doesn't seem to matter.  This happens "sometimes" on the iPhone, or on the Macbook, or on the Windows machine.  Sometimes all at the same time, other times just one one.

- I've tested the lists of which access point the endpoint is connected to, and as far as I can tell it doesn't matter.

- The wired network is fine.   

- Rebooting all the access points seems to clear the problem for a while.   

I'm totally at a loss. Looking for some help!