It's really reliable. Infrastructure and resiliency Telegram some of the best in the world. To establish calls to central servers Telegram Only a short call occurs, after which the call is routed through the Relay server infrastructure, or even goes directly through a p2p connection. Voice call transmission algorithms for Telegram adapted even to work with a weak and unstable Internet connection.
The infrastructure of SIP.TG servers for “landing” calls to virtual PBXs has already been deployed in data centers in Moscow, Frankfurt, Amsterdam, London, Washington, Minsk and is quickly scalable if necessary.
The service has been operating since 2019, during which time many scenarios for its use have been debugged.