But the evidence does look worse for some companies than for others. M-Lab used New York City as one of their case studies. They found that in 2013, internet traffic delivered to Verizon, Time Warner Cable, and Comcast via Cogent took a dramatic hit before rebounding equally dramatically roughly 10 months later:
via the Measurement Lab Interconnection Study
Since all three ISPs took a hit at roughly the same time, it seems easy to look for a common link. In this case, that link would be Cogent. Perhaps the trouble was on their end, instead of at three different companies?
Not so, says M-Lab. The next graph demonstrates that during the same period of time, in the same city, Cablevision’s traffic through Cogent moved smoothly and quickly without taking the same precipitous plunge as the other three providers’.
So that says Cogent was up and running. So perhaps TWC, Comcast, and Verizon all suffered a freak simultaneous set of outages? M-Lab couldn’t rule that out, but they also measured the connections all four last-mile ISPs had to another transit provider, Internap, during the same time period. Those connections did not see any significant degradation.