Connecting the Dots on Internet Congestion


Sometimes when you’re streaming a movie on Netflix, it’ll start pixelating. The quality drops and your crisp HD stream melds into blocky fuzz. It might even drop out altogether. It’s incredibly frustrating – it happens to all of us – and it’s the result of network congestion. Not too many years ago, barely any video worked online. It’s astounding how far we’ve come thanks to adaptive bit rates and better routing techniques that help avoid bottlenecks.

When the system does fail, congestion can be sourced from one of four places: Either it’s a failure in the home network (like your Wi-Fi router), in the last mile network (like your ISP), at core interconnection points (like in a CDN), or it’s a failure with the edge provider (like Netflix). It can be difficult to tell which piece of the puzzle is causing the problem, but if we connect the dots, the source of the congestion becomes clearer.

Last week, three different reports were released that contain technical data to help better understand the source of streaming performance.

The first was the FCC’s 2014 Measuring Broadband America report. The report revealed how well broadband providers are delivering the advertised speeds in their last-mile networks. The FCC found that, on average, almost all ISPs are meeting or beating advertised speeds. So even though peak periods can experience some fluctuations, the congestion is probably not caused by your ISP.

The second was an MIT preliminary report measuring Internet congestion. In their report, MIT data revealed that there was not widespread congestion among the U.S. providers at their interconnection points in the core of the network. So that rules out systemic interconnection failure.

The third report was from a consulting company, NetForecast, which released a report that looked at the Netflix ISP Speed Index – a report from Netflix that analyzes the performance of ISPs. NetForecast concluded that the Netflix ISP Speed Index, which many have used to suggest ISPs are responsible for degradation in streaming quality and chronic congestion, was actually factoring in things ISPs had no control over. Things like choices made by the end-user, available capacity or performance of the Netflix servers, and the performance of the network path between Netflix’s own CDN and the last mile ISPs.

So what do these reports reveal? The FCC shows ISPs are generally over-delivering on speeds in the last-mile. MIT says the core interconnection points are not congested, except those related to Netflix. And Netflix’s own report implicating ISPs turns out to calculate things ISPs have no control over. So if we assume your home network is functioning properly (you can call your ISP to check) these reports confirm that edge providers, in this case Netflix, are a source of persistent congestion which can lead to buffering and a less-than-HD experience. But don’t take our word for it. Listen to the technical experts.