This data does not show the quality of the service when it is up, just whether or not it is responding to packets within 10 seconds. In other words, the connection may be 100% up, and these graphs show 100% availability, yet the connection may be limited to a slow speed, or lagged with up to 10 seconds of latency.

The test works by sending a single ICMP ping to 4.2.2.2 (a highly-available GTE nameserver) every 60 seconds. If no reply is received after 10 seconds, it is counted as 60 seconds of "unavailable" time. Heavy usage of my cable line could possibly produce artificial unavailability, but a 10 second time out should significantly reduce this chance. I consider the accuracy of the data to be better than +/- 5%. I have some ideas to improve this accuracy but for now, for my purposes, this is "good enough". Scroll to the bottom of the page for source code.