Yesterday, just days after its high-profile $16 billion acquisition by Facebook, the Whatsapp messaging service suffered an unprecedented four hours of downtime. Today, founder and CEO Jan Koum came forward to apologize for the downtime, offering technical details and new insight into the scale of the downtime.

"It has been our longest and biggest outage in years and affected all of our users," Koum said in an email to The Verge. According to Koum, the culprit was a faulty network router, which caused a cascading failure that ended up affecting Whatsapp servers. Koum didn't elaborate on the source of the router problems, but the explanation suggests the downtime may not have been related to the new wave of publicity from the Facebook acquisition and the accompanying load on Whatsapp infrastructure. But while the downtime was significant, Koum also indicated the service is taking new measures with its service provider to protect against future downtime and, in Koum's words, "making sure it will not happen again."