My adsl connection had the same downtime as yours in Orleans. As stated the 2am is accounted for.
said by Redfox:After the connection was resumed a new IP address was assigned because I use dynamic one, then my SIP account (voip.ms) failed to register, even I power cycle the ATA
You can try to lower the registration interval from 3600 to 300 in the Linksys ATA to help (if not already done (quicker expiry and refresh with ip changes) Seems to be due to states known on the router.