No, we weren't attacked by Finnish dark metal fans, or slashdotted, or anything of the sort (Coral would have kicked in if that were the case).

Judging from what Nuno dug up in the logs, some kind of power issue at our hosting facility disabled the switch port to which this box was connected, and it only came up again when we asked for the machine to be rebooted - whereupon the Ethernet interface re-initialized the link.

I think the server actually enjoyed the break...

Anyway, I've been wrestling with Asterisk in the meantime (something I've always wanted to set up from scratch at home), and I'm so dog tired that I only just noticed that the tcpdump traces I saved are truncated at the default 96-byte-per-packet mark.