Increasing OpenWrt's default WiFi access point dtim_period

For Developers
1

What would it take to boost the 'dtim_period' default from the current 2 to 3 (or even 5)?

3 is what Apple recommends...

https://blogs.arubanetworks.com/industries/802-11-tim-and-dtim-information-elements/
https://www.sniffwifi.com/2016/05/go-to-sleep-go-to-sleep-go-to-sleep.html
https://www.snbforums.com/threads/dtim-and-beacon-interval-with-iphones.20232/

Smartphones are known to drop incoming non-unicast packets if the AP's DTIM setting is too low.
They do this to stay asleep for longer and thus to save battery power...
Don't expect them to change...

This in turn results in all sorts of various connectivity problems as some ARP/ND/mDNS packets are lost...

I work on Android Networking and I think even 5 wouldn't be necessarily be a bad default value, but we should at least go to 3...

Why is the current default dtim_period '2' (at least per https://openwrt.org/docs/guide-user/network/wifi/basic ) - is this simply coming from hostapd sources? Or is this a deliberate choice on the part of the OpenWrt devs?

3 Likes
2

I just bumped 4 of my APs to 3.

I am by no means well versed in wireless networking but the only thing I would mention is that those articles are from 2016. Maybe whatever is used on the client side (wpa_supplicant?) in android / ios has been updated to handle this.

Like you said, the hostapd.conf default is 2. So maybe they adjusted to work around this as a value of 2 is seen lots "in the real world".

If I notice anything unusual I'll report here.