Default beacon/dtim settings

[Trent Hurt]

What are folks thoughts regarding increasing the beacon interval as well as the dtim interval on a very large byod data ssid? I know the dtim increases for voice but I'm interested in upping those settings on regular data ssid.

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[Amjad Abdullah]

That will require bigger buffer on the AP. The AP buffers the data that the clients poll on DTIM period. If the DTIM period (in milliseconds) is too large, the AP buffer might be overwhelmed faster.

If there is no justifiable reason to increase the DTIM rate or the beacon's interfal I don't see any value of incrasing it.

Rating useful replies is more useful than saying "Thank you"

[George Stefanick]

Understand the value of the DTIM mechanism is to conserve battery life on smaller battery devices. Some vendors, specifically voice vendors spell out very specific DTIM settings. This allows their devices to perform longer. Also note DTIM is for multicast/broadcast delivery. Some applicants get funky when you use extended dtims. Only way to know is to test it .. I don't know I would go more than 3 or so .. But that's just me

As for beacon intervals I wouldn't touch that .. 102 us is default and again some clients get funky if you jack with it ..



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[George Stefanick]

Btw on most devices it states 100, but under the covers 102 is happening.. Sniff some traffic and see .. It's called TBTT

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[Amjad Abdullah]

George Stefanick wrote:
Btw on most devices it states 100, but under the covers 102 is happening.. Sniff some traffic and see .. It's called TBTT

102.4 to be more accurate. LoL.

[George Stefanick]

+5 AA .. Details details details !

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[Scott Fella]

The best practice guides out there has the DTIM set to 2. Again, each vendor has its own best practices. Spectralink requires the WLAN to have a DTIM of 1. I have used DTIM of 2 with no issues and only a handful require and work well with a DTIM higher than that.

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[thefranmanatt]

Why do you want to change this?  What is the end goal?  Any multicast action going on?

CCNP - Wireless
CWNA and CWAP

[Trent Hurt]

I'm just looking/thinking of ways to free up some airtime. I see lots of management traffic in air when I sniff. I also have true byod environment (.edu) so I'm don't want to break any clients by tweaking beacon intervals or dtim. Was just looking for folks opinions on these settings.


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[George Stefanick]

I assume you mean 2.4 GHz ?  DTIM will not save you any airtime.

Here are a few ideas ..

1. Disable lower data rates - make sure your wifi is design as not to create holes

2. Small cells (lower tx power, hide aps out of sight of each other)

3. Proper channel distance (20 dbm)

__________________________________________________________________________________________
"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin
__________________________________________________________________________________________
‎"I'm in a serious relationship with my Wi-Fi. You could say we have a connection."

[Trent Hurt]

Thanks for tips. I have all b data rates disabled. I will look into the tx power settings and start there. This is real issue in hd classrooms etc. I also disable some of the 2.4 radios because of aps running to hot.

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[George Stefanick]

All b rates as in 1,2,5.5 and 11?

If you are deisgning for HD areas here are a few suggestions.

1. try and get 20 clients per ap

2. Use directional anetnnas to shape the RF.

3. Low power (12.5 / 7 mw) in some cases

4. Disable the low rates

5. Depending on your apps you can test client load balance

6. Band steering as well, but test it

Here is the cisco HD design guide

http://www.cisco.com/web/strategy/docs/education/cisco_wlan_design_guide.pdf

__________________________________________________________________________________________
"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin
__________________________________________________________________________________________
‎"I'm in a serious relationship with my Wi-Fi. You could say we have a connection."

[Trent Hurt]

Yes those rates, I try to go 25 or less per ap but I will go less. Cisco load balancing doesn't work with the variety of clients I have. Band select is on but some clients are just bad due to drivers. I have found that moving aps away from entrances/doorways where folks come in and out of the room, helps with some sticky client issues. I have also tried diligently to educate professors to encourage folks to disable unneeded wifi devices when they are proctoring exams over wifi. Ever little bit helps but I understand just like folks on airplanes they ain't really turning them all off. Then you pile on airdisplay mirroring or similar tech. And you can pretty much forgot about a decent quality of experience for end users. "But it works fine at my house". Lol sorry ranting

As always thanks for the insight and links George your truly awesome for the wifi folks on here!!!!

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[George Stefanick]

How many folks do you get in a room that need wifi ?

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[Trent Hurt]

200-300 users with 3-5 devices in large classrooms

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