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Sudden drop in speed and response time across all SSID and radios!


Userlevel 5
Yesterday I had a complaint that a few clients at a remote office were having poor response times. Their ping response time was around 100-400ms, whereas it's usually it's less than 6ms. I could not see any indication that the bandwidth between their facility and ours was stressed. Not really knowing what to try, I rebooted all of their AP's one at a time. The problem seemed to go away, but I am not sure that rebooting things actually solved it.

This morning, I noticed I was having lag myself. I am the main facility where all of the traffic comes back to the controller. I am in a room with an Extreme switch and a 3825i AP. When I plug into the switch, I am getting 1ms response time. Using wireless I am getting anywhere from 30ms to 100ms. It sometimes jumps to 400ms or so (yuck).

I have tried the following to no avail:
Switching SSID's (my guest network and some other segregated ones)
Changing between 802.11n, 802.11bg, and 802.11ac
Switching radio channels (forced from channel 6 to several others)
Rebooting the AP
Looking through EMS Application Flows looking for abuse
Looking through my Wireless admin console for clues (using Reports)
I don't see anything wrong with the general bandwidth at any point in the connection process. It really seems like the controller is doing something fruity out of the blue. I would love to reboot it. But I waited too long into the morning and I would cause pain to a lot of users if I flipped the switch right now.

Can anything think of something that I can check or quickly reset?

I am using 3825i's (80 of them across my facility) and they are Bridged@Controller for the most part. I am running Software version 10.11.02.0032 on a 5210 controller.

Thanks for any clues or advice!!

9 replies

Userlevel 4
Hi Steve,

you can try this before ´making a FW upgrade.

Change the DTIM setting from 5 to 2 in the WLAN Services under advance button.

If it doesn't make it ..then use this article.

https://gtacknowledge.extremenetworks.com/articles/Solution/Wireless-Clients-has-performance-and-con...

Did you made a upgrade shortly ?

There is lot of fixes in the newest code which could also solve the issue.

Regards
Umut Aydin
Userlevel 5
Umut Aydin wrote:

Hi Steve,

you can try this before ´making a FW upgrade.

Change the DTIM setting from 5 to 2 in the WLAN Services under advance button.

If it doesn't make it ..then use this article.

https://gtacknowledge.extremenetworks.com/articles/Solution/Wireless-Clients-has-performance-and-con...

Did you made a upgrade shortly ?

There is lot of fixes in the newest code which could also solve the issue.

Regards
Umut Aydin

Hello Umut. Thanks for the advice. I tried these changes, but they didn't seem to have any affect on the problem. I have not applied a firmware update in quite a while. But I suppose I might as well perform one since I have to reboot everything anyway.
Umut Aydin wrote:

Hi Steve,

you can try this before ´making a FW upgrade.

Change the DTIM setting from 5 to 2 in the WLAN Services under advance button.

If it doesn't make it ..then use this article.

https://gtacknowledge.extremenetworks.com/articles/Solution/Wireless-Clients-has-performance-and-con...

Did you made a upgrade shortly ?

There is lot of fixes in the newest code which could also solve the issue.

Regards
Umut Aydin

Steve, I have this problem every now and again. I have never been able to pinpoint it down myself. It seems like a software issue to me, because I notice it comes and goes and is usually not present right after a reboot. Only after the APs have been up for a few days.

I have actually set my DTIM value to 1. This seems to provide the best user experience in our environment.

Also, if you upgrade to version 10.21 (I suggest you do), they have some wonderful graphs right from the AP configurator.



If you are having an issue, you can check the noise and channel utilization quickly, maybe there is some interference that could also be causing this issue.
Userlevel 1
Umut Aydin wrote:

Hi Steve,

you can try this before ´making a FW upgrade.

Change the DTIM setting from 5 to 2 in the WLAN Services under advance button.

If it doesn't make it ..then use this article.

https://gtacknowledge.extremenetworks.com/articles/Solution/Wireless-Clients-has-performance-and-con...

Did you made a upgrade shortly ?

There is lot of fixes in the newest code which could also solve the issue.

Regards
Umut Aydin

What is the DTIM Setting, and how does changing it from 5 to 2 improve? "Change the DTIM setting from 5 to 2 in the WLAN Services under advance button."
Userlevel 5
Umut Aydin wrote:

Hi Steve,

you can try this before ´making a FW upgrade.

Change the DTIM setting from 5 to 2 in the WLAN Services under advance button.

If it doesn't make it ..then use this article.

https://gtacknowledge.extremenetworks.com/articles/Solution/Wireless-Clients-has-performance-and-con...

Did you made a upgrade shortly ?

There is lot of fixes in the newest code which could also solve the issue.

Regards
Umut Aydin

Yes, if someone could explain the DTIM setting that would be helpful.

I have gone ahead and scheduled an upgrade. I look forward to that new AP view, that looks quite nice!!
Umut Aydin wrote:

Hi Steve,

you can try this before ´making a FW upgrade.

Change the DTIM setting from 5 to 2 in the WLAN Services under advance button.

If it doesn't make it ..then use this article.

https://gtacknowledge.extremenetworks.com/articles/Solution/Wireless-Clients-has-performance-and-con...

Did you made a upgrade shortly ?

There is lot of fixes in the newest code which could also solve the issue.

Regards
Umut Aydin

DTIM is "Delivery Traffic Indication Message". It's a little bit of additional information that is sent out after the normal beacon, broadcast by your APs. The DTIM message causes wireless clients to wake up and read the message. If you set the value to 5, it will transmit a DTIM message every 5th beacon.
Userlevel 4
The DTIM is how the AP (wireless router) warns its clients that it is about to transmit the multicast (and broadcast*) frames it queued up since the previous DTIM.

This queueing and scheduled delivery is done to allow power-conscious devices to save power by turning off their receivers for brief stretches of time, only waking up their receivers when the AP indicates is has traffic for them. This procedure is only performed if one or more of the currently-associated clients on the AP is in power-save mode. If no clients are in power save mode, the AP will transmit "multicasts or broadcasts" as soon as they come in.

A shorter DTIM interval could theoretically make your wireless devices use up their batteries faster, because they'd have to wake up more often for multicasts. A longer DTIM interval could theoretically hinder multicast (and broadcast*) performance on your network.
Userlevel 5
Nathiya Munuswamy wrote:

The DTIM is how the AP (wireless router) warns its clients that it is about to transmit the multicast (and broadcast*) frames it queued up since the previous DTIM.

This queueing and scheduled delivery is done to allow power-conscious devices to save power by turning off their receivers for brief stretches of time, only waking up their receivers when the AP indicates is has traffic for them. This procedure is only performed if one or more of the currently-associated clients on the AP is in power-save mode. If no clients are in power save mode, the AP will transmit "multicasts or broadcasts" as soon as they come in.

A shorter DTIM interval could theoretically make your wireless devices use up their batteries faster, because they'd have to wake up more often for multicasts. A longer DTIM interval could theoretically hinder multicast (and broadcast*) performance on your network.

Hello Nathiya - thank you for that explanation!
Userlevel 5
I updated to the latest code last night, and this morning all seems well again on my network. Response times are normal. Also the controller admin pages are quite snappy, and I remember them lagging a bit as I went through the various menus yesterday. I think there was probably just something funny going on with the controller. Maybe a runaway process or a memory hog of some sort.

Thanks everyone for all the advice and explanations!

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