6 ms·

> You don't need eUICC or anything of the sort to do roaming, which is just what he's describing. Even the behavior with the international prefix on numbers. I

> You don't need eUICC or anything of the sort to do roaming, which is just what he's describing. Even the behavior with the international prefix on numbers. I don’t think the author made this claim at all. He just mentioned that he thinks that Google are using eUICC to make roaming on Google Fi cheaper than traditional roaming agreements. And he’s basing this on the fact that the dat connection can drop out for a little while as the phone roams internationally, presumably because it’s reprogramming the eUICC. I would assume that if you’re running a service like GoogleFi, where the phone number isn’t associated with an actual phone network, then you can do international roaming cheaper because you just setup direct agreements with local telecoms to provide local data access, and then route the “shadow number” assigned to the SIM to a local Google endpoint. Thus you can create a setup where international roam is achieved by having local only carrier agreements, and doing clever call routing to local Google forwarding numbers, which Google then routes over its own network to the destination country, where a local Google endpoint then pushes the call back into the local telco network. Doing this completely removes the need to have a traditional roaming agreement where carrier backhaul alien subscribes back to their home carrier, charging a hefty fee for the privilege. And instead replaces it all with local only call and data routing, with Google infrastructure providing international transit, and Google software masquerading the local subscriber identities, so GoogleFi customers don’t see the messy details underneath.

pxeboot 5y ago
It has been a few years, but when I last used Google Fi, all international roaming was handled by the T-Mobile SIM profile, except when using Three UK, which had it's own profile/shadow number. VoLTE roaming agreements do not exist everywhere, so it is still very common to fall back to 3g for calls when roaming.
jcrawfordor 5y ago
Yeah, I really don't know for sure, I just know that my Fi phone behaves oddly when crossing into Mexico and Canada compared to my Verizon phone a bit ago and I'm guessing it has to do with some of the less typical cost optimization Google does wrt carriers. I don't know a lot of technical detail about how Fi does that and I don't think there's much info about it out there in general, but my theory at least makes sense to me... well-standardized VoLTE and eUICC are pretty recent developments (the same capabilities have existed for much longer but in the form of various proprietary solutions). So this could explain why, early on, Fi was limited to only a few Android devices with bespoke kernels, while nowadays (as VoLTE and eUICC have become much better supported) it works correctly on a much broader range of devices. VoLTE, for example, has been around in concept for longer than LTE, but it has had a complex standards history that I did not try to really explain because it would get lengthy. "VoLTE" and "IMS" can actually refer to different systems (not all VoLTE uses IMS) but it all gets sort of vague and contextual. LTE phones with VoLTE capability have been around basically as long as LTE has been in service in the US, but for a long time were mostly proprietary systems that required per-carrier support. This is still true to some extent but US carriers and device vendors are now much more converged on an IMS-esque architecture than they were even just a few years ago, so it's now a lot more likely that you can e.g. switch to a different carrier and still have VoLTE work... although not guaranteed! One hint that might help reveal how Google Fi handles this is the source of web traffic on my phone... web requests from my phone in Mexico are coming from an IPv4 address registered via ARIN to Airlinq with a contact address in the UK! Airlinq has some kind of relationship to Hong Kong ISP Hutchison and it seems like the takeaway is that they offer a "global cellular mobility" solution. My guess is that Telcel is being used as the mobile provider (I did some checking of intercept recordings which confirms my voice calls at least are going via Telcel) and IP traffic is being routed via Airlinq, whom Google presumably contracts to handle international IP connectivity. Normally, in the US, my traffic emerges via IPv6 from T-Mobile. This is an indication that my traffic is not being tunneled back to the "home" provider as is the typical case with roaming.
ac29 5y ago
> I don’t think the author made this claim at all. He just mentioned that he thinks that Google are using eUICC to make roaming on Google Fi cheaper than traditional roaming agreements. Maybe, but as far as I can tell Google Fi is just a T-mobile MVNO (they used to also use Sprint, but T-mobile bought Sprint ~2 years ago). My direct-with-Tmobile service also includes free international roaming in a ton of countries, so it would make sense if Google just took advantage of the agreements T-mobile already has in place.

pxeboot 5y ago

It has been a few years, but when I last used Google Fi, all international roaming was handled by the T-Mobile SIM profile, except when using Three UK, which had it's own profile/shadow number. VoLTE roaming agreements do not exist everywhere, so it is still very common to fall back to 3g for calls when roaming.

jcrawfordor 5y ago

Yeah, I really don't know for sure, I just know that my Fi phone behaves oddly when crossing into Mexico and Canada compared to my Verizon phone a bit ago and I'm guessing it has to do with some of the less typical cost optimization Google does wrt carriers. I don't know a lot of technical detail about how Fi does that and I don't think there's much info about it out there in general, but my theory at least makes sense to me... well-standardized VoLTE and eUICC are pretty recent developments (the same capabilities have existed for much longer but in the form of various proprietary solutions). So this could explain why, early on, Fi was limited to only a few Android devices with bespoke kernels, while nowadays (as VoLTE and eUICC have become much better supported) it works correctly on a much broader range of devices. VoLTE, for example, has been around in concept for longer than LTE, but it has had a complex standards history that I did not try to really explain because it would get lengthy. "VoLTE" and "IMS" can actually refer to different systems (not all VoLTE uses IMS) but it all gets sort of vague and contextual. LTE phones with VoLTE capability have been around basically as long as LTE has been in service in the US, but for a long time were mostly proprietary systems that required per-carrier support. This is still true to some extent but US carriers and device vendors are now much more converged on an IMS-esque architecture than they were even just a few years ago, so it's now a lot more likely that you can e.g. switch to a different carrier and still have VoLTE work... although not guaranteed! One hint that might help reveal how Google Fi handles this is the source of web traffic on my phone... web requests from my phone in Mexico are coming from an IPv4 address registered via ARIN to Airlinq with a contact address in the UK! Airlinq has some kind of relationship to Hong Kong ISP Hutchison and it seems like the takeaway is that they offer a "global cellular mobility" solution. My guess is that Telcel is being used as the mobile provider (I did some checking of intercept recordings which confirms my voice calls at least are going via Telcel) and IP traffic is being routed via Airlinq, whom Google presumably contracts to handle international IP connectivity. Normally, in the US, my traffic emerges via IPv6 from T-Mobile. This is an indication that my traffic is not being tunneled back to the "home" provider as is the typical case with roaming.

ac29 5y ago

> I don’t think the author made this claim at all. He just mentioned that he thinks that Google are using eUICC to make roaming on Google Fi cheaper than traditional roaming agreements. Maybe, but as far as I can tell Google Fi is just a T-mobile MVNO (they used to also use Sprint, but T-mobile bought Sprint ~2 years ago). My direct-with-Tmobile service also includes free international roaming in a ton of countries, so it would make sense if Google just took advantage of the agreements T-mobile already has in place.