We build Colitu , a VPN with open-source apps for Android , iOS , Windows , Linux and a browser extension . The apps carry traffic over several transports. Hysteria2 is a QUIC-based one that our apps prefer on many networks, because it holds up well on lossy mobile links. The apps also check their own connection. Every 5 seconds they send a small request through the tunnel. If three checks in a row get no answer within 4 seconds, the transport is declared dead, and traffic moves to a T...