I’ve seen if there’s too much buffering or some sort of other issues it drop out and not work. I’ve actually replaced customer CPE to address this. You want to make sure that you are passing ESP through, and there’s even issues with some of the carriers not liking a phone using wifi calling if it has a public IPv4 address (!) I don’t recommend this, but will point out that the carriers have defined SSIDs you may be able to shunt the devices over to, and if you do the open roaming stuff it may also help depending on your environment. ATT_US.bundle/profile.mobileconfig- <string>attwifi</string> Verizon_LTE_US.bundle/profile.mobileconfig- <string>VerizonWiFiAccess</string> You also see this in their config for their SSIDs: <key>DisableAssociationMACRandomization</key> <true/> If you have BYOD but under enterprise management it may make sense to shunt the phones to a discrete SSID which has fewer restrictions. - Jared

On Aug 2, 2024, at 11:10 AM, <chuckchurch@gmail.com> <chuckchurch@gmail.com> wrote:

Hey all, Question if anyone knows about cell phone wi-fi calling in US. Googling isn’t finding what I’m looking for. We have a corporate site in US where users have BYOD capability, and use their phones with wi-fi calling enabled. Site uses a single NAT address (IPv4) for BYOD access. Recently the site reported wi-fi calling had stopped working for all user phones, Apple and Android, all about the same time. The guest network did have some bandwidth limitation applied and they had overuse. That was since resolved, we upped the bandwidth. But the phones all still avoided wi-fi calling. It’s a manufacturing site with known cell signal issues, so most users had no signal via carrier. I did not get a packet capture yet to see what could be going on, we’re 99% sure we’re not blocking traffic. I’m wondering if the phones have an algorithm to test wi-fi signal, and perhaps the carriers will blacklist public IPs with known wi-fi calling issues to avoid cases where an emergency call can’t be made because of intermittent bad performance? It seems odd that even when no bandwidth issues exist, it’s not attempted. Thoughts? Thanks, Chuck Church

My understanding has been that generally, if the cellular network signal was above a certain threshold, phones won't even attempt to use wifi calling. Some carriers used to let you flip a switch to force the phone to prefer wifi over cellular, but some have removed that. ( Verizon for example. ) In my experience some years ago in a similar environment, that cellular threshold to switch was set so low that it was useless. I could be standing in a spot with barely tickling the bottom bar, and nothing. If I flipped to airplane mode, was able to wifi call instantly. On Fri, Aug 2, 2024 at 11:11 AM <chuckchurch@gmail.com> wrote:

Hey all,

Question if anyone knows about cell phone wi-fi calling in US. Googling isn’t finding what I’m looking for. We have a corporate site in US where users have BYOD capability, and use their phones with wi-fi calling enabled. Site uses a single NAT address (IPv4) for BYOD access. Recently the site reported wi-fi calling had stopped working for all user phones, Apple and Android, all about the same time. The guest network did have some bandwidth limitation applied and they had overuse. That was since resolved, we upped the bandwidth. But the phones all still avoided wi-fi calling. It’s a manufacturing site with known cell signal issues, so most users had no signal via carrier. I did not get a packet capture yet to see what could be going on, we’re 99% sure we’re not blocking traffic. I’m wondering if the phones have an algorithm to test wi-fi signal, and perhaps the carriers will blacklist public IPs with known wi-fi calling issues to avoid cases where an emergency call can’t be made because of intermittent bad performance? It seems odd that even when no bandwidth issues exist, it’s not attempted.

Thoughts?

Thanks,

Chuck Church