You're making the assumption that it is all caused by hardware or software malfunction in the sending of an IP packet to the target server. However the first step is usually a DNS lookup. A list would look more like this:
1. DNS lookup fails because the DNS server address configured at the computer OR router is incorrect
2. DNS lookup fails because the configured DNS server is down
3. DNS lookup fails because some firewall is blocking requests to it
4. DNS lookup fails because the network was congested
5. DNS lookup fails because of interference in the Wifi channel from other Wifi networks
6. Etc. Etc.
So indeed, usually when the network is down you only get "DNS lookup failed". Because the actual reason may be complicated. Of course, usually it is due to your computer not being connected to a router so usually the error message hints at that (in layperson's terms: not connected to the internet). So that's why browsers hint at it being your connection, i.e. ethernet or wifi.
But there is no way to make sure. All we know is that DNS seems to fail. The reason it fails could be any part of its configuration which is spread out across physical systems and software components.
The best we can say: probably your ethernet/wifi connection. If we trust that none of the other components are failing then it must be your connection that is failing.
It's like trying to find out what's wrong in 1+2+32+4=10. Sure, it seems like the 32 should be a 3. But maybe the 10 should be a 39. There is no way to tell anymore. All we can do is make an educated guess.
1. DNS lookup fails because the DNS server address configured at the computer OR router is incorrect 2. DNS lookup fails because the configured DNS server is down 3. DNS lookup fails because some firewall is blocking requests to it 4. DNS lookup fails because the network was congested 5. DNS lookup fails because of interference in the Wifi channel from other Wifi networks 6. Etc. Etc.
So indeed, usually when the network is down you only get "DNS lookup failed". Because the actual reason may be complicated. Of course, usually it is due to your computer not being connected to a router so usually the error message hints at that (in layperson's terms: not connected to the internet). So that's why browsers hint at it being your connection, i.e. ethernet or wifi.
But there is no way to make sure. All we know is that DNS seems to fail. The reason it fails could be any part of its configuration which is spread out across physical systems and software components.
The best we can say: probably your ethernet/wifi connection. If we trust that none of the other components are failing then it must be your connection that is failing.
It's like trying to find out what's wrong in 1+2+32+4=10. Sure, it seems like the 32 should be a 3. But maybe the 10 should be a 39. There is no way to tell anymore. All we can do is make an educated guess.