Microsoft will break Internet traffic records this week as it begins to distribute Windows 10, a content delivery expert said Monday.

"Windows 10 ... will easily be the largest day/week of traffic ever on the Internet," said Dan Rayburn, an analyst with Frost & Sullivan who also writes on his own StreamingMediaBlog.com, in a piece posted yesterday.

"Unless Windows 10 is a complete flop and people don't upgrade as quickly as Microsoft expects, Windows 10 is going to create some serious havoc with regards to the user experience," Rayburn contended. "Expect to see some download times in the days, not hours, especially if any other content owners happen to have larger-than-expected traffic at the same time.

"Quality of service for downloads could deteriorate really quickly and remain poor for days, if not longer," Rayburn concluded.

Microsoft plans to hand Windows 10's final code to participants of its Windows Insider program on Wednesday. Insider is a beta project that kicked off last October -- and will continue after the official launch -- that gives the adventurous early builds. For others, all Microsoft has said is that it will roll out Windows 10 in "waves." It has not defined how large those groups will be, when each will receive the upgrade, or how long it will take to get the upgrade in everyone's hands.

The Redmond, Wash. company also plans to pre-load the upgrade on devices whose owners have "reserved" their copies through a nag-and-notification campaign installed on Windows 7 and Windows 8.1. Only after the bits have been silently downloaded to the PC or tablet will Microsoft trigger an alert telling the user that the upgrade is ready to process.

The staggered delivery and pre-loading may alleviate some of the congestion, agreed Rayburn, but he was certain that there would still be problems and delays. "The total usage is just so high ... they need so much, but you can't just double the network," he said in an interview when asked whether Microsoft's approach would help. "There's only a certain amount of capacity [in the Internet]."

According to Rayburn -- and based on conversations he's had with sources -- Microsoft has reserved up to 40Tbps (terabits per second) capacity from multiple "content delivery networks," or CDNs, including Akamai, EdgeCast, Level 3 and Limelight Networks for Windows 10's distribution.

By comparison, Apple's release of iOS 8 last year crested at around 3Tbps and other major Web events, including some of Apple's most widely-watched live-streamed presentations, peaked at 8Tbps, Rayburn said.

On Sept. 17, 2014, when Apple launched iOS 8, its traffic was 50% or more above the norm on many "last-mile" networks within two hours, then soared in the evening to peak at 3Tbps.

"iOS is one of the large-scale events," agreed James DeMent, service line director at Akamai, in an interview. "Windows 10, with the number of devices [eligible] and the amount of demand, has that same type of buzz."

The massive surge in download traffic -- Microsoft's reserved 13 times what Apple maxed out at with iOS 8 -- will jam up many ISPs' (Internet service providers) capacity at "interconnection points," the junctions where the ISP's network connects to the Internet backbone or to other carriers. "ISPs already know that their interconnection points in some cities are going to be overloaded," said Rayburn.

To maintain an acceptable quality of service (QoS) for their customers, not all of whom will be seeking Windows 10 but streaming audio or video or simply browsing the Web, ISPs will "rate limit" the speed of the Windows 10 downloads, Rayburn added. In other words, although someone may have a 40Gbps (gigabit per second) connection to the Internet through their ISP, the 3GB Windows 10 download will not be reaching them at that rate.

Microsoft has been unable to get more capacity, Rayburn said, because the Windows 10 roll-out, with interest fueled by the free upgrade deal, is a one-time event: CDNs were hesitant to allocate more to Microsoft because doing so would have impacted their ongoing customers. "That's part of the reason why it has not been capable of handling this," said Rayburn.

Although the anticipated slowdown of downloads may not be visible to most customers -- for the simple fact that Microsoft is delivering the upgrade in the background -- the congestion will stretch out the time it takes Microsoft to get the upgrade to X number of users.

That hints at a longer release schedule than many may expect or hope for.

The huge scale of the event could also affect the Internet in general. "I've never used the term 'break the Internet' because most of the time people say that, they are simply overhyping an event on the Web," said Rayburn. "But with the volume of downloads that Microsoft is expecting and the capacity they have already reserved to deliver the software, the Internet is in for some real performance problems this week."

Akamai, the CDN Rayburn believed would have the largest share of Microsoft's Windows 10 business, declined to speak about specific companies, much less customers. But DeMent was willing to talk in general terms.

"If something isn't delivered or configured properly, it could take down the intercontinental Internet," said DeMent.

When asked about staggered delivery and pre-loading -- approaches Microsoft will employ to disseminate Windows 10 -- DeMent noted that both are used when large amounts of the right kind of content is moved through the Internet.

"No one wants anyone to wait for 24 hours to download something," DeMent said of staggering distribution. "[And] pre-loading is a tactic that content owners use to try to manage the environment. You can't throw money at the pipe," he said, referring to the fact that not everyone has a fast 100Gbps connection to the Internet.

Microsoft has wanted to get a jump on the Windows 10 release by flipping on the download switch on Saturday, said Rayburn, but postponed that -- one of several such delays. As of Monday morning, Rayburn said the plan was to begin at 4 p.m. ET that day.

Such a head start would not have been noticeable to most users, since Microsoft is pushing the Windows 10 bits in the background to PCs, and presumably when the devices are otherwise not busy, as it does with updates and security patches.

Those ahead-of-time machinations have already had an effect on the Internet as a whole, Rayburn asserted. "One of the networks had a major outage this week, and it did have to do with [Windows 10]," he said. "They were trying to free up capacity on their network. So it's impacting their customers even though it's not out yet."

Computerworld was unable to confirm that downloads had begun arriving on any of several Windows 7 and Windows 8.1 devices.