What Happens When You Download Movie On Netflix

[Patrice Mieczkowski]

Ipulled this chapter together from dozens of sources that were at times somewhat contradictory. Facts on the ground change over time and depend who is telling the story and what audience they're addressing. I tried to create as coherent a narrative as I could. If there are any errors I'd be more than happy to fix them. Keep in mind this article is not a technical deep dive. It's a big picture type article. For example, I don't mention the word microservice even once :-)

Given our discussion in the What is Cloud Computing? chapter, you might expect Netflix to serve video using AWS. Press play in a Netflix application and video stored in S3 would be streamed from S3, over the internet, directly to your device.

Another relevant factoid is Netflix is subscription based. Members pay Netflix monthly and can cancel at any time. When you press play to chill on Netflix, it had better work. Unhappy members unsubscribe.

The client is the user interface on any device used to browse and play Netflix videos. It could be an app on your iPhone, a website on your desktop computer, or even an app on your Smart TV. Netflix controls each and every client for each and every device.

Everything that happens before you hit play happens in the backend, which runs in AWS. That includes things like preparing all new incoming video and handling requests from all apps, websites, TVs, and other devices.

In 2007 Netflix introduced their streaming video-on-demand service that allowed subscribers to stream television series and films via the Netflix website on personal computers, or the Netflix software on a variety of supported platforms, including smartphones and tablets, digital media players, video game consoles, and smart TVs.

Netflix succeeded. Netflix certainly executed well, but they were late to the game, and that helped them. By 2007 the internet was fast enough and cheap enough to support streaming video services. That was never the case before. The addition of fast, low-cost mobile bandwidth and the introduction of powerful mobile devices like smart phones and tablets, has made it easier and cheaper for anyone to stream video at any time from anywhere. Timing is everything.

Building out a datacenter is a lot of work. Ordering equipment takes a long time. Installing and getting all the equipment working takes a long time. And as soon they got everything working they would run out of capacity, and the whole process had to start over again.

The long lead times for equipment forced Netflix to adopt what is known as a vertical scaling strategy. Netflix made big programs that ran on big computers. This approach is called building a monolith. One program did everything.

What Netflix was good at was delivering video to their members. Netflix would rather concentrate on getting better at delivering video rather than getting better at building datacenters. Building datacenters was not a competitive advantage for Netflix, delivering video is.

It took more than eight years for Netflix to complete the process of moving from their own datacenters to AWS. During that period Netflix grew its number of streaming customers eightfold. Netflix now runs on several hundred thousand EC2 instances.

The advantage of having three regions is that any one region can fail, and the other regions will step in handle all the members in the failed region. When a region fails, Netflix calls this evacuating a region.

The header image is meant to intrigue you, to draw you into selecting a video. The idea is the more compelling the header image, the more likely you are to watch a video. And the more videos you watch, the less likely you are to unsubscribe from Netflix.

The first thing Netflix does is spend a lot of time validating the video. It looks for digital artifacts, color changes, or missing frames that may have been caused by previous transcoding attempts or data transmission problems.

A pipeline is simply a series of steps data is put through to make it ready for use, much like an assembly line in a factory. More than 70 different pieces of software have a hand in creating every video.

The idea behind a CDN is simple: put video as close as possible to users by spreading computers throughout the world. When a user wants to watch a video, find the nearest computer with the video on it and stream to the device from there.

In 2007, when Netflix debuted its new streaming service, it had 36 million members in 50 countries, watching more than a billion hours of video each month, streaming multiple terabits of content per second.

At the same time, Netflix was also devoting a lot of effort into all the AWS services we talked about earlier. Netflix calls the services in AWS its control plane. Control plane is a telecommunications term identifying the part of the system that controls everything else. In your body, your brain is the control plane; it controls everything else.

In 2011, Netflix realized at its scale it needed a dedicated CDN solution to maximize network efficiency. Video distribution is a core competency for Netflix and could be a huge competitive advantage.

The number of OCAs on a site depends on how reliable Netflix wants the site to be, the amount of Netflix traffic (bandwidth) that is delivered from that site, and the percentage of traffic a site allows to be streamed.

Within a location, a popular video like House of Cards is copied to many different OCAs. The more popular a video, the more servers it will be copied to. Why? If there was only one copy of a very popular video, streaming the video to members would overwhelm the server. As they say, many hands make light work.

Right now, up to 100% of Netflix content is being served from within ISP networks. This reduces costs by relieving internet congestion for ISPs. At the same time, Netflix members experience a high-quality viewing experience. And network performance improves for everyone.

What may not be immediately obvious is that the OCAs are independent of each other. OCAs act as self-sufficient video-serving archipelagos. Members streaming from one OCA are not affected when other OCAs fail.

If Netflix freezes or gets stuck loading but the rest of your device is working, you can often fix the problem with these basic troubleshooting steps. This usually happens when data stored on your device needs to be refreshed, or when a network issue stops Netflix from loading.

This issue can happen when there's a problem with the domain name system (DNS) server your device connects to. For help fixing a DNS issue, you'll need to contact your internet service provider (ISP).

Everything, before you hit play, happens in the backend, which runs in AWS. That includes things like preparing all new incoming videos and handling requests from all apps, websites, TVs, and other devices.

Netflix succeeded. Netflix executed well, but they were late to the game, which helped them. By 2007 the internet was fast and cheap enough to support streaming video services. That was never the case before. The addition of fast, low-cost mobile bandwidth and the introduction of powerful mobile devices like smartphones and tablets has made it easier and cheaper for anyone to stream video at any time from anywhere. Timing is everything.

What Netflix was good at was delivering videos to its members. Netflix would rather concentrate on getting better at delivering video rather than getting better at building data centers. Building data centers was not a competitive advantage for Netflix; delivering video is.

It took over eight years for Netflix to complete moving from its data centers to AWS. During that period, Netflix grew its number of streaming customers eightfold. Netflix now runs on several hundred thousand EC2 instances.

I am fascinated by our guest author, Todd Hoff\u2019s ability to distill complex topics into simpler discussions. This is one of our inspirations for why we made the ByteByteGo newsletter in the first place.

He\u2019s been a programmer for over 30 years, having worked in Silicon Valley his entire career. He worked with various companies, including NEC, System Industries, IBM, Sun Microsystems, and Yahoo, to name a few.

I\u2019d like to thank Netflix for being so open about its architecture. Over the years, Netflix has given hundreds of talks and written hundreds of articles on the inner workings of how they operate. The whole industry is better for it.

Another reason for going into so much detail on Netflix is that Netflix is just plain fascinating. Most of us have used Netflix at one time or another. Who wouldn\u2019t love peeking behind the curtain to see what makes Netflix tick?

Open Connect handles everything that happens after you hit play. Open Connect is Netflix\u2019s custom global content delivery network (CDN). Open Connect stores Netflix videos in different locations worldwide. When you press play, the video streams from Open Connect to your device and is displayed by the client. Don\u2019t worry; we\u2019ll talk more about what a CDN is a little later.

Netflix controls your video viewing experience from beginning to end. That\u2019s why it just works when you click play from anywhere in the world. You reliably get the content you want to watch when you want to watch it.

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