My ADSL connection went down this morning. This is a fairly rare occurrence, as my ISP is Mailbox, a tiny but fabulous company, which has an excellent reliability record and tremendous support. But, they (like other ADSL providers in the UK) are ultimately dependent upon BT for the service, and BT manages to screw things up with monotonous regularity.
I called Mailbox support, and they told me that they had got other reports and were looking into it. A short while later they had a fix. When I got back home, I tried applying the fix, but I still wasn't seeing the outside world on the net. As an aside, the BBC and Google must get no end of traffic from people testing whether their connection is working. The assumption is that either your connection is broken, or the world as we know it has ended. I remember hearing that standard procedure for people sheltering in a nuclear bunker is to try to tune into BBC Radio 4. If you can't get it, a nuclear holocaust must have happened. Or the batteries in your radio have died. [Meanwhile, back at my story...] I called Mailbox tech support again. The guy I spoke to thought that my problem probably wasn't related to the BT screw up, and prepared to report it to BT. He suggested that I might try (as a last resort) power-cycling the ADSL router. So, I gave it a try, and after a period of flashing lights of myriad colours, behold - the connection was restored!
I'm beginning to think that almost all technical problems can be solved by quitting and restarting (software), plugging and unplugging (network), or power-cycling (hardware).