Why Use a CDN for Live Streaming?

It is important to use a CDN for Live Streaming because CDN (Content Delivery Network) consists of servers strategically located worldwide that store copies of your video and distribute it out to viewers based on their location (or CDN footprint). CDNs improve the performance of live streaming by caching files closer to users, so streams don’t buffer or break up under high traffic loads.

So, is your live streaming experience interrupted by buffering, slowdowns, stream interruptions, or other glitches? Then, using a CDN is a great way to ensure that these issues don’t happen. CDNs have been around for a while now, and they are only getting more popular and important to live streaming as time goes on.

In this post, we will talk about why you should use a CDN for your next live streaming event and how it will positively impact your end users’ experience.

But, first off, why do you need a CDN?

Do I Need a CDN for Live Streaming?

The short answer is, yes! Using a CDN will help you

  • serve a large geographically distributed audience,
  • reduce the load on your origin server,
  • reduce latency,
  • reduce video buffering,
  • provide security against DDoS attacks,
  • and much more!

But, do you understand why a CDN helps improve your live streaming? To understand that, first, lets take a look at what a CDN is and how they work.

What is a CDN?

As mentioned earlier, a CDN or Content Delivery Network consists of servers strategically located around the world that store copies of your video and distribute it out to viewers based on their location. What does this mean?

Well, if you are producing your live stream in San Fransisco, and a large section of your audience is in Singapore, then the CDN closest to Singapore will cache or store your content and serve it to them. Thus, they experience faster download speeds because their requests do not have to travel all the way to the US and back. This short travel time translates to a better viewing experience.

Should I use a CDN for Live Streaming
Left: No CDN and Right: with a CDN. Credit: Wikipedia

CDNs improve live streaming by caching files closer to users, so streams don’t buffer or break up as often under high traffic loads for those without reliable broadband connections.

They also serve media locally rather than having multiple requests travel over expensive long-haul links back and forth across the globe while data centers try to figure out where each viewer is geographically located.

Here is a simplified guide to how CDNs work – it will give you a deeper understanding of the benefits that you get by using a CDN for serving your content (both Live and VOD).

Before we dig deep into the benefits of CDN technologies, let us quickly understand ABR streaming – a type of video streaming that has enabled the delivery of high quality video while adapting to the user’s bandwidth conditions. And, the way ABR works is well suited to CDN-based delivery.

Let’s see how in the next section.

ABR Video Streaming and CDNs

ABR Video Streaming using HTTP-based streaming protocols have enabled the use of CDNs for video streaming. In ABR live streaming, the output from the encoder is chopped into chunks or segments and then delivered to the video players with the help of a live manifest file. The manifest file indicates the names and locations of the video segments, and the players use the manifest to request video depending on the playback position.

CDN for Live Streaming

The video segments along with the playlist/manifest are stored on the origin server and this is connected to the CDN.

Whenever the player requests a segment, the request first goes to the CDN that checks its local cache to see if the segment has been cached/stored. If the segment is not in the CDN cache (cache miss), the CDN forwards the request to the origin/web/live streaming server that returns the segment. The CDN caches the segment and also serves it to the client that requested it.

By using small video chunks and HTTP requests, it is very easy to cache videos on CDNs and deliver them using Adaptive Bitrate streaming technology to video players around the world.

In summary, the use of ABR and CDNs have revolutionized the world of OTT Video Streaming and delivered great benefits to both the producer and the consumer.

But, what are these benefits? Let’s look at them in the next section.

What are the Benefits of using a CDN for Live Streaming?

There are significant benefits to using a CDN for Live Streaming video content to your audience because they will directly impact their viewing experience and help you gain and retain your followers & audience.

In this section, let’s look at a few of these benefits in detail, shall we?

CDNs Reduce The Load on Live Streaming Servers

By sitting in between the live streaming server (which could be your laptop, even!) and the large audience you are streaming to, the CDN essentially protects your infrastructure by taking the load off of it. Every request from your audience’s devices first goes to the CDN, which serves them, and only if the requested video segment is not in the CDN’s cache will the CDN ask the origin server (your laptop) to serve the video segment. Without the CDN in-between, it’s quite possible that your live stream would have crashed along with your laptop quite quickly!

stampede gif
Requests bombarding your serve without a CDN to protect it!

Using a CDN Reduces Latency or Start-up Delay for Live Streaming

When your audience is far away from your live streaming location, you need to factor in the round-trip time required to access the video segments. When someone presses play and have to wait 20-30 seconds for the video to start, they will likely abandon the stream and go somewhere else.

Related:  How to Live Stream to YouTube using OBS Studio

For this reason, you use a CDN that can serve the first segment of video from a server close to the audience’s location. This greatly reduces the time required to respond to a request, reduces download times, and reduces the latency or start-up delay. All of this is very important to ensure a great user experience!

Reduce Buffering in Live Streaming using a CDN

Why does a video player buffer? So, when a player requests the streaming server for a segment of the video, a certain amount of time is spent waiting for that segment of video to reach the player from the server. While the player is waiting for the video segment to arrive, if its buffer gets emptied (plays back all the video in its buffer), then the buffer is said to “underflow,” and the player starts to buffer. This can happen if the streaming server is overloaded with requests and cannot serve every player quickly.

However, if you use a CDN, then the requests do not go all the way to the streaming server; and instead, they are served by the CDN itself. This reduces the response time for each segment, and thus the player’s buffers are replenished quickly when you use a CDN for live streaming.

Protect your Live Streaming Infrastructure from DDoS Attacks

As you’ve learned by now, a CDN sits between the audience and your origin or live streaming server. It acts like a barrier or the first line of defense, which is very useful in preventing DDoS attacks on origin servers. Commercial CDNs have a lot of intelligence built into them, and if they detect malicious traffic or a Distributed Denial of Service (DDoS) attack, then the CDN will block those IP addresses or clients.

In the absence of a good CDN, all these malicious requests would have come to your streaming server and your infrastructure would have been overwhelmed and crashed.

Higher Quality Video Streaming by using a Live Streaming CDN

A CDN’s fast response time ensures that a player can request high bitrate video chunks when its bandwidth is good and be certain that it will receive the segments in time to prevent buffer underflow. This is critical for high-quality ABR streaming, where the player has the independence to choose a segment from any profile of the bitrate ladder. Without a good CDN or a Live Streaming Server, the basic advantage of using ABR streaming goes away!

Should You Use a Multi-CDN for Live Streaming

By now, you are convinced that using a CDN for Live Video Streaming is a great decision that will protect your infrastructure from attacks and provide your audience with a fantastic viewing experience.

But, here is a question for you. What will happen if your CDN provider fails or crashes? That would be a terrible thing to happen because your audience is watching your live stream via the CDN, which has turned into a point-of-failure!

To guard against such problems, some companies use a multi-CDN architecture where multiple different CDN vendors are used to serve the video to the end-users. This is simply a form of redundancy with intelligence built into it.

In a multi-CDN architecture, if one of the CDN companies fails or is facing issues, then the traffic is seamlessly picked up by the other CDN providers that are part of the multi-CDN setup. You can also take advantage of the pricing of the different CDN vendors based on the time of the day or geographies and lower your costs. Learn more about Multi-CDNs here.

While using a multi-CDN architecture is not mandatory for small live streaming events, if you are hosting the Olympics, a large concert, or a high-traffic live streaming event, it’s worth considering using a multi-CDN architecture for your live streaming.

If you are interested in learning more, here is a simple guide to how Multi-CDNs work and the different ways in which they can be configured.

In conclusion, will you use a CDN for Live Streaming?

As we come to the end of this article, what are you going to do? Are you going to use a CDN for live streaming or not? Most online video streaming platforms have partnerships with CDN companies, and this gives them better deals and tighter integrations with CDN providers.

The next time you choose a live streaming platform, make sure you ask the provider this simple question – “which CDN are you using to serve your content to the end-users?”. This simple question can get you a lot of information about how the platform performs.

Until next time, thank you, take care, and happy streaming!

krishna rao vijayanagar
Krishna Rao Vijayanagar

I’m Dr. Krishna Rao Vijayanagar, and I have worked on Video Compression (AVC, HEVC, MultiView Plus Depth), ABR streaming, and Video Analytics (QoE, Content & Audience, and Ad) for several years.

I hope to use my experience and love for video streaming to bring you information and insights into the OTT universe.

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