What protocol are you referring to? Tails makes a lot of great efforts to prevent undesired network access but at the end of the day it doesn't do any isolation

What protocol are you referring to? Tails makes a lot of great efforts to prevent undesired network access but at the end of the day it doesn't do any isolation by virtualisation and the bundled video player was able to ping a server directly. I don't believe this approach would be possible against Qubes OS.