WiFi calling and iPhones
11-05-2019 10:30 AM
Greetings. I'm experiencing an issue where iPhones aren't consistantly utilizing WiFi calling. Network is a master / local deployment on 220.127.116.11 with AP225's. SSID is BYOD 802.1x with WMM enabled. Android phones have no issues. Apple phones sometimes will build the WiFi calling tunnel, but completely random. My personal iPhone XR (Verizon) always shows the WiFi calling icon at home with my Instant AP, no problems. At work, rarely, though occasionally, I will see the icon. I took a packet capture off my phone for an hour today, turning WiFi calling off / on, updating the emergency address, rebooting phone - never did it send the DNS query for wo.vzwwo.com or attempt port 4500 connection to anything. If I look at the DMZ firewall I can see that several devices corporate-wide have established port 4500 connections to Verizon IP's, So we're not preventing this by any means. My question is...does Apple use some sort of logic to assess the cellular signal quality before it activates WiFi calling? Or likewise, does it do some sort of assessment at the RF level to determine whether or not the WiFi environment is suitable for WiFi calling? I'm stumped over this.