More succinctly, in a Cloudflare CEO tweet: "The teams at @verizon and @noction should be incredibly embarrassed at their failings this morning which impacted @Cloudflare and other large chunks of the Internet. It’s absurd BGP is so fragile. It’s more absurd Verizon would blindly accept routes without basic filters." For more details, see How Verizon and a BGP Optimizer Knocked Large Parts of the Internet Offline Today | Cloudflare Blog
"Cloudflare Chief Technology Officer John Graham-Cumming told the Washington Post that Verizon failed to intercept the issue from a fiber-optic network services provider. This caused a routing leak that led to the widespread system outage.Customers report Verizon, Cloudflare disruptions | Washington Post
“Normally a large network would do some kind of filtering,” Graham-Cumming said. “But in this case, [Verizon] passed it on.”
Because of this, Verizon customers lost large chunks of internet access and passed on the faulty information to other networks like Cloudflare, Graham-Cumming said. This affected 10 percent of Cloudflare’s traffic."