[kemals]

This comment is spot on. This is asynchronous nature of the computer networks. While it is easy to control the path within smaller or enterprise networks, it is very likely that the reverse path on the internet is going to be different compared to forwarding path. Following that, the real challenge is, in case that you are dealing with some issue, to detect where the issue is, given that it might be happening on the reverse path that you don't have visibility into.