25 Jun
2020
25 Jun
'20
10:07 a.m.
Hi
I have not been digging into this too much, but I have a few clues which could be helpful.
* Swisscom branded mobile phones (Samsung at least) prevent WiFi (or VoLTE) calling (HD Audio) from being used when SIM cards of other operators are used. (Maybe Swisscom uses a specific flavour of WiFi calling or VoLTE which is incompatible to others?)
* Sunrise, for sure uses IPSEC for WiFi calling but uses GeoIP filter to only allows this service from Swiss IP Addresses.
Sidenote: Sunrise Mobile CGNat cannot handle GRE protocol.
-Benoît-