5 ms·

I always wondered - can you have no roaming if you use eSIM with wifi calling and an exit node in country where eSIM is issued? So, basically: - you bought eSI

by ewuhic 2y ago

I always wondered - can you have no roaming if you use eSIM with wifi calling and an exit node in country where eSIM is issued? So, basically: - you bought eSIM in Germany - you are currently in US - you use tailscale with exit node at your apartment in Germany - voila, no roaming when you call German mobile lines Right? [EDIT FOR ADDITIONAL QUESTION] If I have troubles receiving SMSs from Germany to German number while in US, would wifi calling icrease the chances of receiving the said SMSs?

Ghoelian 2y ago
Are there even roaming costs at all when calling over wifi? Would make sense to me if there weren't, since you're not using the mobile infrastructure you would be paying for. Then again I could also easily see telcos charging roaming anyway, just because they can.
- simtel20 2y ago
  There's also a technical hurdle of the telco can't know where you're coming from over the Internet. The terminate your end of the vowifi call and from there they only charge for the connection as though it originated in their network, which is all they know for sure (that is their SIM and your account that's authenticated from somewhere in the world)
  - lxgr 2y ago
    Well, I know at least one provider that looks at your IP's country registration and will block you if they believe it's not domestic: Vodafone Germany. I wouldn't wish their service upon my worst enemies.
    - simtel20 2y ago
      Sounds terrible. So yeah, I guess they can make an educated guess, and initiate a demoralizing cat and mouse game with their customers.
- miki123211 2y ago
  Calls can freely be handed over between VoLTE and VoWiFi, depending on signal quality, and that often happens without the user's knowledge or explicit consent. This means that "no roaming costs over WiFi" is a very dicy proposition, as a carrier either needs to restrict handovers (and I don't even know if that's allowed by the spec, not to mention the implications of dropping calls when going out of WiFi Range), cover the costs themselves, or move them onto the unsuspecting user if a handover happens.
winterswift 2y ago
In my experience, wi-fi calling works as if on the home network, regardless of IP location/endpoint. So this would work similarly with an eSIM.
- netsharc 2y ago
  I have a dual-SIM Pixel 7, the eSIM "slot" has a data-only subscription, the other slot has a pay-as-you-go SIM that I can make phone calls with (I make so few phone calls to actual lines, that having credit that I can top-up every few months is much more cheaper than paying monthly for free minutes). The PAYG SIM offers WiFi calling, and the phone appears to even offer "WiFi"-calling over the data connection, for a much better audio quality.
- lxgr 2y ago
  At least Vodafone Germany intentionally blocks (or used to block) foreign IPs for their gateway. I'll always trust them to needlessly ruin perfectly fine technologies. Fortunately, as far as I remember at least iPhones route VoWiFi traffic over a VPN, if any is connected, so that's one way to still use it abroad.
  - miki123211 2y ago
    This is actually less unreasonable than it seems at first. The Vo WiFi spec only defines handover procedures for networks that implement VoLTE, but VoLTE roaming was historically almost nonexistent, although the situation is improving somewhat. This means that if you go out of range of your WiFi router, your cell phone has no idea how to request a handover from the network, and the call drops.
    - lxgr 2y ago
      By that logic, shouldn't they never have rolled out VoWLAN as long as they still have some non-LTE covered areas in Germany either? Also, I'd much prefer a call getting dropped to suddenly changing from being included to billed when traveling abroad.
- 2y ago
gruez 2y ago
Yes, see: https://news.ycombinator.com/item?id=42768735 https://news.ycombinator.com/item?id=42768735
aimazon 2y ago
> If I have troubles receiving SMSs from Germany to German number while in US, would wifi calling icrease the chances of receiving the said SMSs? I'm not up to date on the state of messaging infrastructure but it used to be the case that some providers would offer non-standard methods for sending messages over their network to intermediary providers. Rather than sending an SMS to a number, a business would ask the intermediary to send a message and the intermediary would use the non-standard method provided by the network provider. The non-standard methods work fine if you're connected to the network directly but if you're overseas that will not be the case and so you can't receive these non-standard messages. Don't quote me on any of that, though.
- lxgr 2y ago
  The non-standard method is to get the SMS to a delivering SMSC (which is the same network component that's used for mobile originated SMS delivery, which is standardized). Once it's enqueued in an SMSC, there is no more distinction between how it got there, as far as I understand (at least downstream from there; delivery reports to the sender might again be proprietary for non-mobile senders). > The non-standard methods work fine if you're connected to the network directly but if you're overseas that will not be the case and so you can't receive these non-standard messages. This is actually not particular to the way in which SMS have been enqueued, but rather to how they're delivered: The sending SMSC has to "dial" pretty deep into both the recipient's home and visited network in the original implementation. This means that they need a commercial agreement and technical integration with both of them. Usually, problems/inconsistencies occur when they do know how to deliver to the recipient number's home network (because if they can't, they'd probably have rejected the message at SMSC submission time), but are then redirected to a given visited network with which they don't have interconnectivity. This problem (and some others, including serious privacy concerns) is solved by a newer technology called "SMS home routing". In that model, there's something like a proxy in the recipient's home network that essentially poses as the receiving phone to the sending SMSC, and then uses the home network's resources to do actual delivery. This usually leads to more consistent experiences, and allows things like a "received message log". (Without a home router, the recipient's home network never sees the message content when the recipient is roaming!)
Gormo 2y ago
Alternatively, use a global eSIM purely for data access, then use your phone as a SIP client (or use something like Google Voice) for PSTN access, eschewing the mobile network entirely.
lxgr 2y ago
Many providers actually let you use Wi-Fi calling without any VPN, i.e. they don't arbitrarily restrict the set of allowed IPs that can connect to their Internet gateway. > If I have troubles receiving SMSs from Germany to German number while in US, would wifi calling icrease the chances of receiving the said SMSs? Probably not, unless your provider supports inbound and outbound SMS via ISM. If you have an iPhone, you can check whether yours does in Settings -> About -> Tap the name of your carrier. (If it lists "Voice and SMS", you might be good; if it's only "voice" or nothing at all, SMS will go over the visited network.)
phh 2y ago
I'm implementing a fully libre open-source vowifi/volte client for Android that runs in JVM sandbox, rather than untrustable modem. During my development I went through a protocol detail that I was too lazy to implement: you're supposed to announce which is the last 4g cell you saw even when doing Vowifi. I just hardcoded a value and forgot about it. And then, I get a user who tells me that their carrier is saying they are roaming, even though they don't. I'm a tad clueless at first, because they are the network, they ought to know (this even happen over VoLTE). I send them an updated implementation that reports the correct cell. And then they receive a "welcome back" SMS. Anyway, it's possible that your carrier can do abroad vowifi, you just need your vowifi client to lie as to where it is.
- stavros 2y ago
  Is there a link to this client? I'd be interested to play around with it.
  - phh 2y ago
    https://github.com/phhusson/ims https://github.com/phhusson/ims
    - stavros 2y ago
      Thanks.
- LaF0rge 2y ago
  In case it's of interest, please see https://osmocom.org/projects/foss-ims-client/wiki/VoWiFi_with_Asterisk https://osmocom.org/projects/foss-ims-client/wiki/VoWiFi_wit... for an existing way how to talk to VoWiFi carriers from entirely free/libre/open-source software. It's basically a hacked-up version of Asterisk that has IMS client support, plus a modified strongswan IPsec client.
  - phh 2y ago
    Thanks. In case that's of interest, I have another one, using doubango rather than asterisk: https://github.com/phhusson/doubango/ https://github.com/phhusson/doubango/ (and its readme at https://github.com/phhusson/doubango/blob/master/README-phh https://github.com/phhusson/doubango/blob/master/README-phh )

by ewuhic 2y ago

Ghoelian 2y ago

Are there even roaming costs at all when calling over wifi? Would make sense to me if there weren't, since you're not using the mobile infrastructure you would be paying for. Then again I could also easily see telcos charging roaming anyway, just because they can.

simtel20 2y ago
There's also a technical hurdle of the telco can't know where you're coming from over the Internet. The terminate your end of the vowifi call and from there they only charge for the connection as though it originated in their network, which is all they know for sure (that is their SIM and your account that's authenticated from somewhere in the world)
- lxgr 2y ago
  Well, I know at least one provider that looks at your IP's country registration and will block you if they believe it's not domestic: Vodafone Germany. I wouldn't wish their service upon my worst enemies.
  - simtel20 2y ago
    Sounds terrible. So yeah, I guess they can make an educated guess, and initiate a demoralizing cat and mouse game with their customers.
miki123211 2y ago
Calls can freely be handed over between VoLTE and VoWiFi, depending on signal quality, and that often happens without the user's knowledge or explicit consent. This means that "no roaming costs over WiFi" is a very dicy proposition, as a carrier either needs to restrict handovers (and I don't even know if that's allowed by the spec, not to mention the implications of dropping calls when going out of WiFi Range), cover the costs themselves, or move them onto the unsuspecting user if a handover happens.

winterswift 2y ago

In my experience, wi-fi calling works as if on the home network, regardless of IP location/endpoint. So this would work similarly with an eSIM.

netsharc 2y ago
I have a dual-SIM Pixel 7, the eSIM "slot" has a data-only subscription, the other slot has a pay-as-you-go SIM that I can make phone calls with (I make so few phone calls to actual lines, that having credit that I can top-up every few months is much more cheaper than paying monthly for free minutes). The PAYG SIM offers WiFi calling, and the phone appears to even offer "WiFi"-calling over the data connection, for a much better audio quality.
lxgr 2y ago
At least Vodafone Germany intentionally blocks (or used to block) foreign IPs for their gateway. I'll always trust them to needlessly ruin perfectly fine technologies. Fortunately, as far as I remember at least iPhones route VoWiFi traffic over a VPN, if any is connected, so that's one way to still use it abroad.
- miki123211 2y ago
  This is actually less unreasonable than it seems at first. The Vo WiFi spec only defines handover procedures for networks that implement VoLTE, but VoLTE roaming was historically almost nonexistent, although the situation is improving somewhat. This means that if you go out of range of your WiFi router, your cell phone has no idea how to request a handover from the network, and the call drops.
  - lxgr 2y ago
    By that logic, shouldn't they never have rolled out VoWLAN as long as they still have some non-LTE covered areas in Germany either? Also, I'd much prefer a call getting dropped to suddenly changing from being included to billed when traveling abroad.
2y ago

gruez 2y ago

Yes, see: https://news.ycombinator.com/item?id=42768735 https://news.ycombinator.com/item?id=42768735

aimazon 2y ago

> If I have troubles receiving SMSs from Germany to German number while in US, would wifi calling icrease the chances of receiving the said SMSs? I'm not up to date on the state of messaging infrastructure but it used to be the case that some providers would offer non-standard methods for sending messages over their network to intermediary providers. Rather than sending an SMS to a number, a business would ask the intermediary to send a message and the intermediary would use the non-standard method provided by the network provider. The non-standard methods work fine if you're connected to the network directly but if you're overseas that will not be the case and so you can't receive these non-standard messages. Don't quote me on any of that, though.

lxgr 2y ago
The non-standard method is to get the SMS to a delivering SMSC (which is the same network component that's used for mobile originated SMS delivery, which is standardized). Once it's enqueued in an SMSC, there is no more distinction between how it got there, as far as I understand (at least downstream from there; delivery reports to the sender might again be proprietary for non-mobile senders). > The non-standard methods work fine if you're connected to the network directly but if you're overseas that will not be the case and so you can't receive these non-standard messages. This is actually not particular to the way in which SMS have been enqueued, but rather to how they're delivered: The sending SMSC has to "dial" pretty deep into both the recipient's home and visited network in the original implementation. This means that they need a commercial agreement and technical integration with both of them. Usually, problems/inconsistencies occur when they do know how to deliver to the recipient number's home network (because if they can't, they'd probably have rejected the message at SMSC submission time), but are then redirected to a given visited network with which they don't have interconnectivity. This problem (and some others, including serious privacy concerns) is solved by a newer technology called "SMS home routing". In that model, there's something like a proxy in the recipient's home network that essentially poses as the receiving phone to the sending SMSC, and then uses the home network's resources to do actual delivery. This usually leads to more consistent experiences, and allows things like a "received message log". (Without a home router, the recipient's home network never sees the message content when the recipient is roaming!)

Gormo 2y ago

Alternatively, use a global eSIM purely for data access, then use your phone as a SIP client (or use something like Google Voice) for PSTN access, eschewing the mobile network entirely.

lxgr 2y ago

Many providers actually let you use Wi-Fi calling without any VPN, i.e. they don't arbitrarily restrict the set of allowed IPs that can connect to their Internet gateway. > If I have troubles receiving SMSs from Germany to German number while in US, would wifi calling icrease the chances of receiving the said SMSs? Probably not, unless your provider supports inbound and outbound SMS via ISM. If you have an iPhone, you can check whether yours does in Settings -> About -> Tap the name of your carrier. (If it lists "Voice and SMS", you might be good; if it's only "voice" or nothing at all, SMS will go over the visited network.)

phh 2y ago

I'm implementing a fully libre open-source vowifi/volte client for Android that runs in JVM sandbox, rather than untrustable modem. During my development I went through a protocol detail that I was too lazy to implement: you're supposed to announce which is the last 4g cell you saw even when doing Vowifi. I just hardcoded a value and forgot about it. And then, I get a user who tells me that their carrier is saying they are roaming, even though they don't. I'm a tad clueless at first, because they are the network, they ought to know (this even happen over VoLTE). I send them an updated implementation that reports the correct cell. And then they receive a "welcome back" SMS. Anyway, it's possible that your carrier can do abroad vowifi, you just need your vowifi client to lie as to where it is.

stavros 2y ago
Is there a link to this client? I'd be interested to play around with it.
- phh 2y ago
  https://github.com/phhusson/ims https://github.com/phhusson/ims
  - stavros 2y ago
    Thanks.
LaF0rge 2y ago
In case it's of interest, please see https://osmocom.org/projects/foss-ims-client/wiki/VoWiFi_with_Asterisk https://osmocom.org/projects/foss-ims-client/wiki/VoWiFi_wit... for an existing way how to talk to VoWiFi carriers from entirely free/libre/open-source software. It's basically a hacked-up version of Asterisk that has IMS client support, plus a modified strongswan IPsec client.
- phh 2y ago
  Thanks. In case that's of interest, I have another one, using doubango rather than asterisk: https://github.com/phhusson/doubango/ https://github.com/phhusson/doubango/ (and its readme at https://github.com/phhusson/doubango/blob/master/README-phh https://github.com/phhusson/doubango/blob/master/README-phh )