Over the past several weeks my internet has been "dropping" for hours at a time. After looking into why it's not working it appears to be a DNS resolution issue so techinically I am connected. After a while it comes back and things are happy.
To debug if it's a DNS issue on my end or the DNS servers I'm using, I did some testing. I am using open dns or google dns servers. I reenabled my old internet connection on the same physical interface of my router as the AT&T connection. And... it works with the same DNS servers. I switch back to AT&T, it doesn't work.
Something tells me AT&T deep packet inspection software is strongly looking at DNS resolution requests and is having issues. Considering that I'm using the same DNS servers on both my connections it's clear that it's an AT&T issue. AT&T better fix their service.
For reference, I work in the software industry and used to run a network device driver team so I'm not incompetent and understand networking and networking related issues well.
Apparently AT&T's DNS servers don't support SRV records. At least the ones I pulled via DHCP didn't. So connecting to Google Talk via an external jabber client (like Pidgin) won't work. Switching to OpenDNS solved the problem instantly.
It strikes me as pretty odd that our 'bleeding edge' fiber internet access can be impacted by outdated and possibly unreliable old school DNS servers.
The DNS issue with Pidgin and Google Talk is actually a problem with the Motorola NVG589 gateway. Its DNS server is 126.96.36.199, so I tested it vs the router's (because I've had the same problem since switching to giga power).
This is the command and response I got from the router: