How Netflix serves 200 Billion hours of video every year

Netflix published its first engagement report in December 2023. It counted nearly 100 billion hours viewed in six months, from January to June 2023.

Every one of those hours is video sent to somebody's screen. Netflix sends all of it through its own network, called Open Connect.

So where does that network keep the video?

Servers inside your internet provider

Netflix began Open Connect in 2011. By then it was a significant portion of the traffic on consumer internet providers' networks.

The building block is a cache server called an Open Connect Appliance, or OCA. It stores encoded video files and serves them to devices over HTTP.

Netflix gives these servers free of charge to qualifying internet service providers (ISPs). Netflix provides the hardware. The ISP provides power, space and connectivity.

This is a content delivery network, or CDN. A CDN brings the content people watch close to where they're watching it.

Each server feeds the people near it

The aim is to shorten the network and geographical distance the video travels during playback.

Take a viewer whose ISP hosts an OCA. They press play, and the request goes to Netflix's services in AWS.

Those services check authorization and licensing. Then they pick an OCA by its files, its health and its network proximity to the viewer.

The device gets a URL for that OCA and asks it for the files. The ISP controls which of its customers are routed to its own OCAs.

The OCA itself doesn't store client data such as viewing history. It reports its status to AWS and serves files.

What goes on the server?

The files on an OCA are temporary. New files are added every night.

Netflix calls this fill. It runs in off-peak windows and uses bandwidth that viewers aren't using.

This works because Netflix can predict what its members will watch. It can also predict the time of day they will watch it.

Popularity algorithms decide how the content is spread across the servers. They also keep down the number of updates each server needs.

OCAs can download updates from each other. That reduces the use of internet backbone capacity during the update.

The device does its share

A video isn't one file. Netflix's playback services work out which files a request needs.

They take two things into account: the device's characteristics and the current network conditions.

The device keeps adjusting after that. It optimizes what the OCA serves, based on its own needs and the network at that moment.

How much traffic takes the short path?

Netflix gave two numbers in March 2016.

Open Connect delivered 100% of its video traffic. That was over 125 million hours of viewing a day.

Close to 90% of that traffic went over direct connections between Open Connect and members' ISPs.

A direct connection can be an OCA inside the ISP. It can also be an OCA at an internet exchange point where the ISP is present.

Once OCAs are installed in an ISP's data centre, almost all Netflix content is served from them.

Summary

1. Netflix counted nearly 100 billion hours viewed from January to June 2023.
2. Open Connect is Netflix's own CDN, begun in 2011. It delivers 100% of Netflix's video traffic.
3. An Open Connect Appliance is a cache server that stores encoded video files.
4. Netflix gives OCAs free of charge to qualifying ISPs. The ISP provides power, space and connectivity.
5. Netflix's services in AWS check licensing and pick the OCA. The OCA only serves the files.
6. New files are added to OCAs every night, in off-peak windows.
7. In March 2016, close to 90% of Netflix's traffic went over direct connections to members' ISPs.

Sources

1. Open Connect Overview, Netflix.
2. How Netflix Works With ISPs Around the Globe to Deliver a Great Viewing Experience, Ken Florance, Netflix, 17 March 2016.
3. What We Watched: A Netflix Engagement Report, Netflix, 12 December 2023.