Comment by Spivak

In a packet-switched network there isn't one connection between you and your peer. Even if you had line monitoring that wouldn't be enough on its own to tell you that your packet can't get there -- "routing around the problem" isn't just a turn of phrase. On the opposite end networks are best-effort so even if the line is up you might get stuck in congestion which to you might as well be dropped.

You can get the guarantees you want with a circuit switched network but there's a lot of trade-offs namely bandwidth and self-healing.