Network outages vary in scope and cause, from the Egyptian Internet shutdown in Feb. 2011 and natural disasters such as October 2012 Hurricane Sandy and the Mar. 2011 Japanese earthquake, to the thousands of small, daily outages.
Outages matter because they allow us to judge the reliability of the Internet directly, and they sometimes allow us to infer things about the real world (like how widespread was a natural disaster).
We use Trinocular, our active probing system to track outages across the Internet, adaptively probing all /24 address blocks where at least 15 address reply to pings (as of 2016: that’s about 4.1M blocks!). We develop new algorithms to identify outages and cluster them to events, providing the first visualization of outages. Finally, we report on Internet stability as a whole, and the size and duration of typical outages, using core-to-edge observations. We find that about 0.3% of the Internet is likely to be unreachable at any time, suggesting the Internet provides only 2.5 ``nines’’ of availability.
We have studied outages in the January/February Internet outage in Egypt corresponding to the Egyptian revolution, the March 2011 Tohoku earthquake off the coast of Japan, and the October 2012 Hurricane Sandy on the east coast of the U.S. We have a technical report describing our analysis of Hurricane Sandy. We recently studied the 2017 Hurricane Harvey.
Our approach is described in the peer-reveiwed paper: