> how do you predict ahead of time whether your software will run on congested networks?
One thing you can do is build in "bad network emulation" into your software, allowing the various pieces to drop packets, delay packets, reorder packets, etc. and make sure it still behaves reasonably with all this garbage turned up.
RE ".... build in "bad network emulation" into your software....." I expect there would be network emulators that would be able to emulate these situations. How good these emulators are would be the next question.
One thing you can do is build in "bad network emulation" into your software, allowing the various pieces to drop packets, delay packets, reorder packets, etc. and make sure it still behaves reasonably with all this garbage turned up.