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Does anyone have any resources which explain why eSIMs tunnel your network traffic to the provider? My mental model for old fashioned physical SIMs is that they

Does anyone have any resources which explain why eSIMs tunnel your network traffic to the provider? My mental model for old fashioned physical SIMs is that they would roam on the network you're visiting. ie, a Chinese physical SIM on a US network would show up from the US network, and would otherwise be normal except that the phone and network traffic would be very expensive. My understanding of eSIMs is that they act more like a VPN; your network (and phone?) traffic is tunneled back to the home network.

lxgr 2y ago
> My mental model for old fashioned physical SIMs is that they would roam on the network you're visiting. No, that's never really been the case. It's technically possible (and called "local breakout"), but for various reasons I also don't fully understand, it's usually not done that way. One is legal liability for user actions; another is accessibility of services at home, such as banking apps, that are probably more comfortable with a familiar IP.
SSLy 2y ago
That's not ordered by the SIM but by the packet-core network policies set by both parties.
daveoc64 2y ago
It's not really anything to do with eSIM. If you used a physical SIM from the same carrier with the same settings, you'd have the same experience. When connecting via a cellular data network, all data will be routed via your carrier's Access Point Name (https://en.wikipedia.org/wiki/Access_Point_Name https://en.wikipedia.org/wiki/Access_Point_Name). Most carriers only have servers in their home region capable of handling the traffic. It is possible to have regional servers for this, but most carriers don't bother with the expense. Roaming data is usually expensive or restricted in usage - so there's traditionally been very little demand for higher speed connectivity. Travel eSIMs are usually just a regular SIM with a very limited plan from a carrier that has favourable roaming deals.
- everdrive 2y ago
  Thanks for this explanation -- I guess I really had things wrong.
jenny91 2y ago
I think this is a peculiarity of the short-term travel eSIM providers (like Airalo). If I recall correctly, when I went to Bermuda, the Airalo eSIM would route the traffic through Isle of Man. They have some of the most odd agreements with random telecoms to get coverage and cheap rates. Partly I think it's skirting around local regulations (e.g. if a country required SIMs to be registered with the owner's information, but you provision the SIM from a nearby country's telco and route traffic through there maybe you can get around it). But as far as I understand this has nothing to do with eSIMs and a lot to do with Airalo trying to cover every corner of the world for cheap.
deleted 2y ago
[deleted]
smoovb 2y ago
Routing data back to the home network is how it can get counted and charged for. The host roaming network is just selling in bulk, but does not own the customer.

lxgr 2y ago

> My mental model for old fashioned physical SIMs is that they would roam on the network you're visiting. No, that's never really been the case. It's technically possible (and called "local breakout"), but for various reasons I also don't fully understand, it's usually not done that way. One is legal liability for user actions; another is accessibility of services at home, such as banking apps, that are probably more comfortable with a familiar IP.

SSLy 2y ago

That's not ordered by the SIM but by the packet-core network policies set by both parties.

daveoc64 2y ago

It's not really anything to do with eSIM. If you used a physical SIM from the same carrier with the same settings, you'd have the same experience. When connecting via a cellular data network, all data will be routed via your carrier's Access Point Name (https://en.wikipedia.org/wiki/Access_Point_Name https://en.wikipedia.org/wiki/Access_Point_Name). Most carriers only have servers in their home region capable of handling the traffic. It is possible to have regional servers for this, but most carriers don't bother with the expense. Roaming data is usually expensive or restricted in usage - so there's traditionally been very little demand for higher speed connectivity. Travel eSIMs are usually just a regular SIM with a very limited plan from a carrier that has favourable roaming deals.

everdrive 2y ago
Thanks for this explanation -- I guess I really had things wrong.

jenny91 2y ago

I think this is a peculiarity of the short-term travel eSIM providers (like Airalo). If I recall correctly, when I went to Bermuda, the Airalo eSIM would route the traffic through Isle of Man. They have some of the most odd agreements with random telecoms to get coverage and cheap rates. Partly I think it's skirting around local regulations (e.g. if a country required SIMs to be registered with the owner's information, but you provision the SIM from a nearby country's telco and route traffic through there maybe you can get around it). But as far as I understand this has nothing to do with eSIMs and a lot to do with Airalo trying to cover every corner of the world for cheap.

deleted 2y ago

[deleted]

smoovb 2y ago

Routing data back to the home network is how it can get counted and charged for. The host roaming network is just selling in bulk, but does not own the customer.