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Comcast Blames Internet Outage on DNS Traffic Overload

Comcast said the failure of some hardware on is backbone that caused local DNS (domain name system) servers to overload was the culprit for an Internet outage (opens in new tab) that affected the MSO’s customers on the West coast Monday night. 

Following an outage that left service unavailable or degraded for several hours, Comcast restored service to most customers by about 9 p.m. PT.

“A piece of hardware in our backbone network failed yesterday morning,” Mark Muehl, Comcast’s SVP of platform technologies, explained in this blog post apologizing for the outage and noting that Comcast is giving a credit to customers who were impacted. “Hardware issues of this sort are fairly commonplace and redundancy in our network addressed any immediate concern.  Most backbone networks, including Comcast’s, are designed to heal themselves and route traffic along alternate paths much like a detour would route automobile traffic around a street closed for construction.”

He said the issue arose when Internet traffic that “shifted in an unexpected way” overloaded local DNS server capacity. Comcast, he said, has been working to resolve the problem and has brought additional DNS capacity online in the affected areas to prevent it from occurring again. 

"We know that having a fast, reliable connection to the Internet is vital and that interruptions of this sort are unacceptable. We’re sorry that we didn’t live up to that last night," Muehl said. 

For Comcast, the outage happened at particularly inopportune time, coming amid a new American Customer Satisfaction Index report finding that satisfaction ratings for pay TV, Internet and wireless offerings have reached seven-year lows. Comcast, which has launched a big program aimed at improving customer service and the overall customer experience, fell in the latest ACSI rankings.