4 ms·

I wonder how this works, if your cellular gets deactivated, how do you inform the service that you've watched the ad? Particularly if all you have is an app wit

I wonder how this works, if your cellular gets deactivated, how do you inform the service that you've watched the ad? Particularly if all you have is an app with no access to low-level system APIs like USSD, texting etc. Is it just disabling your access except to a particular IP range and then enabling it back on receiving a HTTP request? Can routing in Telcos even work like that? Or is it DNS perhaps? That would seem to be the easiest layer to implement this on. I'd really like a technical explanation here.

mbreese 3y ago
> Can routing in Telcos even work like that? Why not? I don’t know how this company actually has things setup, but I suspect you’re right — it’s all done with routing tables. DNS tends to cache too much, and I think DHCP would either be too chatty or also cache too much to be used as a gate keeper. Instead, a firewall/routing approach would make more sense. It would technically be no more difficult than setting up port knocking. Instead of pinging a specific port, you’d watch a video. But other after that, you could just route traffic. What I’d be more interested in knowing is where this filtering is taking place. It would be better done on the phone, to avoid null-routed data going over the network (and costing $/€/etc). So, I’m guessing that it is all done within the eSIM app itself. Maybe something like getting a (signed) token after viewing the video that extends a time limit/expiration for the eSIM itself. Then when the eSIM is expired, it can only communicate with one service — the ad host.
lathiat 3y ago
It’s just the cellular version of a wifi captive portal: https://en.wikipedia.org/wiki/Captive_portal https://en.wikipedia.org/wiki/Captive_portal Simple version is the network router firewalls traffic to anything except the ad server, and the ad server will have a trigger to change the firewall. There are some technical nuances to how you handle DNS and also redirecting from other web pages (if desired) without breaking things. But that’s the gist of it.
__jonas 3y ago
I'm assuming this would be done by zero-rating their advertising service. They already imply that they restrict traffic on their Free plan to certain services so I would assume they use the same mechanism to allow traffic to pass through their advertising service even when a users free plan has run out. Here is a paper on how websites could be identified for zero-rating: https://www.researchgate.net/publication/343966537_Knocking_on_IPs_Identifying_HTTPS_Websites_for_Zero-Rated_Traffic https://www.researchgate.net/publication/343966537_Knocking_... It has a whole list of possible methods.
worewood 3y ago
As a citizen of a country where prepaid access is the norm, it's just DNS (mis)redirection. People call it "captive portal". When your quota runs out everything you access resolves to the same address, which is an internal web site where you can buy more data. And yes, it does not work if you use a custom DNS such as Cloudflare or Google Public DNS, or if you try to reach a HTTPS page. But they don't care, as it's a minority that does this. Android already has support for captive portals, and shows a notification when it detects one.
projektfu 3y ago
Various providers seem to allow access to their sites when the SIM card isn't set up yet, so you can set it up. Seems to be a solved problem.
deeth_starr_v 3y ago
All your traffic routes through the cell to their gateway. The gateway has session info and can pass/block traffic

mbreese 3y ago

> Can routing in Telcos even work like that? Why not? I don’t know how this company actually has things setup, but I suspect you’re right — it’s all done with routing tables. DNS tends to cache too much, and I think DHCP would either be too chatty or also cache too much to be used as a gate keeper. Instead, a firewall/routing approach would make more sense. It would technically be no more difficult than setting up port knocking. Instead of pinging a specific port, you’d watch a video. But other after that, you could just route traffic. What I’d be more interested in knowing is where this filtering is taking place. It would be better done on the phone, to avoid null-routed data going over the network (and costing $/€/etc). So, I’m guessing that it is all done within the eSIM app itself. Maybe something like getting a (signed) token after viewing the video that extends a time limit/expiration for the eSIM itself. Then when the eSIM is expired, it can only communicate with one service — the ad host.

lathiat 3y ago

It’s just the cellular version of a wifi captive portal: https://en.wikipedia.org/wiki/Captive_portal https://en.wikipedia.org/wiki/Captive_portal Simple version is the network router firewalls traffic to anything except the ad server, and the ad server will have a trigger to change the firewall. There are some technical nuances to how you handle DNS and also redirecting from other web pages (if desired) without breaking things. But that’s the gist of it.

__jonas 3y ago

I'm assuming this would be done by zero-rating their advertising service. They already imply that they restrict traffic on their Free plan to certain services so I would assume they use the same mechanism to allow traffic to pass through their advertising service even when a users free plan has run out. Here is a paper on how websites could be identified for zero-rating: https://www.researchgate.net/publication/343966537_Knocking_on_IPs_Identifying_HTTPS_Websites_for_Zero-Rated_Traffic https://www.researchgate.net/publication/343966537_Knocking_... It has a whole list of possible methods.

worewood 3y ago

As a citizen of a country where prepaid access is the norm, it's just DNS (mis)redirection. People call it "captive portal". When your quota runs out everything you access resolves to the same address, which is an internal web site where you can buy more data. And yes, it does not work if you use a custom DNS such as Cloudflare or Google Public DNS, or if you try to reach a HTTPS page. But they don't care, as it's a minority that does this. Android already has support for captive portals, and shows a notification when it detects one.

projektfu 3y ago

Various providers seem to allow access to their sites when the SIM card isn't set up yet, so you can set it up. Seems to be a solved problem.

deeth_starr_v 3y ago

All your traffic routes through the cell to their gateway. The gateway has session info and can pass/block traffic