Wi-fi drop issues

[amolivad]

Hey there everyone,

I'm going out on a limb here and i'm wondering if i can get any input on this...

 

I am having wireless issues at a grade school my company manages. I am one of the technicians that's been working on the issue. To give you a little background, the school is using two different types of chromebooks:

• Samsung CE303C12 (uses a/b/g/n)
  
• Acer C738T (uses a/b/g/n/ac)
  

Both of these devices are able to connect to the wireless networks fine up until two weeks ago when the school introduced a new SSO application for the chromebooks. The application they are using now is called Clever. Now there are two different ways you can authenticate to Clever, the first is through an email address and a password or the other way is through the SSO method which utilizes a QR code tied to each of the students. This is where things get interesting....

 

Method one on Wi-Fi (signing in with a Clever email address and password) *Note* this was done in a classroom on 1 Meru AP pushing out a/b/g

all 25 students connect to clever with an email address and password. They are able to load all of the applications perfectly fine, there are no connection drops, and all of the pings to the AP are in the 20-25ms range.

 

Method two on Wi-Fi (using the QR code)*Note* this was done in a classroom on 1 Meru AP pushing out a/b/g

The students all hold there QR code up to the webcam and it signs them in. about 7-10 students in the connection starts to really degrade and students are getting hung up on logging in or the webpage they're trying to access times out. I noticed when the students are signing in im getting pings from the AP in the 200-2000ms range and i am dropping packets. eventually i can get everyone at least signed in, but then the connection is so poor you can't load any apps, or web pages for that matter.

 

Troubleshooting:

Note: the tests performed were done on several maru AP's (all the same model, firmware version, etc.)

 

1. Called clever and tried to see if there were addresses that needed to be whitelisted for clever SSO (there were 3 IP's)
   
2. Tested the two different models on 3 different AP's (all AP's are the same and had the same settings) on 3 different channels and got the same results
   
3. After hours, we shut down all of the AP's in the building and tried to connect them to just a single AP (got the same results) we also tested it with different wireless security because we were told clever for whatever reason my not like WPA2-PSK-TKIP so we used WPA2-PSK-CCMP instead.
   
4. Checked RSSI levels with Acrylic Wi-Fi Professional and all the chromebooks had great signal. -40 - -50
   
5. Checked to make sure the chromebooks weren't bouncing to other neighboring AP's
   
6. Turned off the content filter and opened up the wi-fi to see if the chromebooks would be able to connect (still didn't work)
   

 

There's a lot more that we tried as well but still cant get the chromebooks to connect up to the wireless and be efficient using the Clever QR SSO. If anyone has any information that may be useful please send it my way. I have also contacted maru support and sent them multiple wireless pcaps of when we're replicating the issue and they have been completely useless. they just keep messing with band steering and the power levels.

Edited February 11, 2017 by amolivad

[AlanD]

OK, so you need to eliminate the MERU access points. get something cheap and cheerful off ebay, buy a an ubiquiti AP (and sell it again afterwards)....borrow one...bring your broadband router from home and use it as an access point - just to make check to see its your network or the wireless. If its the wireless - then MERU needs to sort it - which they should be really keen to do - because I bet you pay a fortune annually to them and you won't be paying them after you realise that it might be cheaper to swap all your access points for "ac" ubquiti ones and save yourself those annual charges.

[ReBoot]

Why don't you get some USB - Ethernet adaptors and connect one or more Chromebooks to your wired network. These are pretty cheap (under£10) and work pretty well. I use them for tablet software builds.

 

https://www.amazon.co.uk/Ethernet-Adapter-Macbook-Chromebook-Windows/dp/B00MYT481C/ref=sr_1_1?ie=UTF8&qid=1487112323&sr=8-1-spons&keywords=usb+ethernet&psc=1

 

This would give you a strong indication whether the issue is with your wireless access or elsewhere.

 

I would also look at the AP instrumentation to see what load its reporting - may give an indication of whether the AP is the bottleneck or clients are hanging waiting for a remote resource.

 

As a starter I'd highly recommend comparing wired and wireless access using a USB adaptor.

[Bruce123]

Hey there everyone,

I'm going out on a limb here and i'm wondering if i can get any input on this...

 

I am having wireless issues at a grade school my company manages. I am one of the technicians that's been working on the issue. To give you a little background, the school is using two different types of chromebooks:

• Samsung CE303C12 (uses a/b/g/n)
  
• Acer C738T (uses a/b/g/n/ac)
  

Both of these devices are able to connect to the wireless networks fine up until two weeks ago when the school introduced a new SSO application for the chromebooks. The application they are using now is called Clever. Now there are two different ways you can authenticate to Clever, the first is through an email address and a password or the other way is through the SSO method which utilizes a QR code tied to each of the students. This is where things get interesting....

 

Method one on Wi-Fi (signing in with a Clever email address and password) *Note* this was done in a classroom on 1 Meru AP pushing out a/b/g

all 25 students connect to clever with an email address and password. They are able to load all of the applications perfectly fine, there are no connection drops, and all of the pings to the AP are in the 20-25ms range.

 

Method two on Wi-Fi (using the QR code)*Note* this was done in a classroom on 1 Meru AP pushing out a/b/g

The students all hold there QR code up to the webcam and it signs them in. about 7-10 students in the connection starts to really degrade and students are getting hung up on logging in or the webpage they're trying to access times out. I noticed when the students are signing in im getting pings from the AP in the 200-2000ms range and i am dropping packets. eventually i can get everyone at least signed in, but then the connection is so poor you can't load any apps, or web pages for that matter.

 

Troubleshooting:

Note: the tests performed were done on several maru AP's (all the same model, firmware version, etc.)

 

1. Called clever and tried to see if there were addresses that needed to be whitelisted for clever SSO (there were 3 IP's)
   
2. Tested the two different models on 3 different AP's (all AP's are the same and had the same settings) on 3 different channels and got the same results
   
3. After hours, we shut down all of the AP's in the building and tried to connect them to just a single AP (got the same results) we also tested it with different wireless security because we were told clever for whatever reason my not like WPA2-PSK-TKIP so we used WPA2-PSK-CCMP instead.
   
4. Checked RSSI levels with Acrylic Wi-Fi Professional and all the chromebooks had great signal. -40 - -50
   
5. Checked to make sure the chromebooks weren't bouncing to other neighboring AP's
   
6. Turned off the content filter and opened up the wi-fi to see if the chromebooks would be able to connect (still didn't work)
   

 

There's a lot more that we tried as well but still cant get the chromebooks to connect up to the wireless and be efficient using the Clever QR SSO. If anyone has any information that may be useful please send it my way. I have also contacted maru support and sent them multiple wireless pcaps of when we're replicating the issue and they have been completely useless. they just keep messing with band steering and the power levels.

 

I would agree a good starting point would be to eliminate (or not) Meru, by connecting them to another AP from another vendor for example.

 

I would also try connecting a small number of devices (using the QR card method) to see the problem relates to number of devices trying to connect simultaneously.

 

You mention ping times, where are you pinging? Maybe it's a problem further down the line (not between AP and device).

 

But, off-the-top-of-my head it would seem to be a contention issue, with too many devices trying to send/receive too much data.

 

If this SSO works by simply and crudely sending multiple pictures or even video from the webcam to a server until authenticated, then this could generate an awful lot of data per Chromebook. Multiply it by the number of Chromebooks and you potentially have a problem.

 

If the SSO is an App, then maybe it can't do any local processing (doesn't have permission) and has no option other than to stream the video / photos over wireless to a server?

 

The fact that you don't experience any issues with the other (text-based) authentication method suggests this could be the problem.

 

Go to Monitoring -> Wireless Statistics on the controller and check for high Channel utilization, high Loss % and high Retry % on the particular AP/band they are connected to. These values are updated every 60 seconds. If these look high during this period, then it could indicate an issue with contention.

 

Kind Regards,

 

Bruce.

Edited February 20, 2017 by Bruce123

[AlanD]

Overloading certainly seems to fit the facts.....so I'm happy to back that idea up.

[fredbayker]

I'd start off with a just a few clients and see how it goes. If you're having issues with just a few clients it may not be down to overloading.

If it works well with a few, keep adding clients until you notice some degradation.