My network disconnect problems seem to have got better over the last few days. Since Friday I have only had a single disconnect:
At the same time, the number of cell hops diminished greatly. In 18 hours I had only the following reports:
Aug 26 15:19:55 nerd-gw fstats: +CGREG 1 81E3 8FC48E8
Aug 27 01:29:19 nerd-gw fstats: +CGREG 2
Aug 27 01:29:19 nerd-gw fstats: +CGREG 1 81E3 8FC48E8
Aug 27 09:07:45 nerd-gw fstats: +CGREG 2
Aug 27 09:07:45 nerd-gw fstats: +CGREG 1 81E3 8FC48E8
Aug 27 09:13:55 nerd-gw fstats: +CGREG 1 81E3 8FC8F2E
I still don't understand the link-level disconnects, but they're practically invisible. More interesting is that between Aug 26 15:19:18 and Aug 27 09:13:55 cell ID 8FC8F2E didn't show up at all. Is there a connection?
It didn't stay that way. In the course of the day the number of hops increased, and shortly before midnight there was another disconnect. In this case, though, the device didn't disappear. Instead, I find:
Aug 27 23:28:24 nerd-gw ppp: tun0: LCP: deflink: LayerDown
Aug 27 23:28:24 nerd-gw ppp: tun0: LCP: deflink: SendTerminateAck(6) state = Opened
Unless I'm very much mistaken, this is a disconnect explicitly requested by the other end.
So it seems we have at least reasons for disconnects: hardware problems with the dongle, where it goes away and comes back, and explicit disconnect requests from the other end. There's also the question of cell hopping and occasional very short link-level disconnects, which may or may not be related.