Microsoft has made Verizon Communications the centerpiece of its effort to build out a worldwide network to speed up video delivery for users of its Azure cloud computing service.

To some, the move comes a bit of a surprise. Microsoft had been building out this network itself, according to observers, but now appears to have reversed course. When it comes to internet infrastructure, giant Web players like Microsoft typically build out their own offerings, rather than relying on service providers such as Verizon. And in recent years, these content delivery networks, or CDNs, have seen some big build-outs. When you're Netflix and Google, it helps to have full control of your CDN, so that you can more efficiently deliver a significant slice of the internet's Sunday evening data.

And Microsoft has already successfully built out a different CDN, to speed up delivery of its own web pages, videos, and monthly software updates. But the Azure network—built for customers rather than the company's internal use—was a different type of project, says Dan Rayburn, a streaming media expert and blogger.

A Verizon spokeswoman confirmed to WIRED Monday that the company's Digital Media Services CDN network is used by Microsoft and its Azure group, and according to Microsoft the traffic will be on the EdgeCast CDN, which Verizon purchased in 2013. Microsoft told WIRED, "We are happy to partner with EdgeCast to provide an integral component of the Azure Media Services workflow."

But dumping its internal effort makes sense for Microsoft, says Rayburn, who first broke the news of the Microsoft-Verizon deal. Azure's biggest competitor, Amazon, has been offering CDN services—built on its very own delivery network—to cloud users for years. However, Microsoft was late to the game and offered a bare-bones product, Rayburn says. The Verizon deal, "gets them to market faster with a solution that has more capacity," he says.

It also shows that there is constant flux, even in this era of do-it-yourself web giants.