Its DPI mostly from this company: https://theins.ru/en/politics/265749

It won't be the only solution that can do this by the way. Many airplane WiFi services block WhatsApp and telegram calls.

I think they just look at the traffic shape. Real-time traffic requires a lot of constant similar sized traffic per second, rather than texting or images which is much more bursty.

Time to learn more on DPI, thanks.

If you want to explore and make some tests of your own, nDPI is the most popular open-source DPI engine.

https://github.com/ntop/nDPI

https://youtu.be/NndEp7__Y1A

Hi, I was wondering how is it technically possible for Russia firewalls to block calls over these platforms, while keeping chat messages working? Thanks

My guess is that it is because of a different layer 7 protocol than HTTP is used for calls, and the code of the protocol leaks in the TLS/SSL header. Is this guess correct?

Ngl same question for United Arab Emirates