A few months back I opened a service ticket because my FIOS internet would drop out intermittently for 15-30 seconds at a time. Verizon closed the ticket yet the problem persisted.
I then noticed that even when the internet was down, I still had VOIP service. That pointed to a workstation problem. I finally went to Event Viewer and sure enough, the event had been logged.
The problem was related to the Intel integrated ethernet power and wake-up options. I've disabled them and haven't had a problem since.