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How content delivery systems work on streaming platforms like Netflix and Spotify

CDN technology is in higher demand than ever before due to the constant weighting of content on the Internet.

netflix on a macbook sitting on a table
Image: Unsplash

Back in the ’90s, the problem of server congestion emerged all over the world. When a large number of remote clients were connected, the servers could not produce query results in a short time.

They lacked CPU power, memory capacity, or network transmission speed. If the site’s server was on another continent, the user would have to wait for the content to load in bits and pieces, losing a lot of time while waiting.

As a result, some businesses began to distribute servers globally to reduce site traffic. The closer the server is to the client who made the request, the faster he will receive a response in the form of a web page with content.

The content delivery network (CDN), a server-based network architecture designed to expedite content delivery to end-users, was born out of this.

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Because CDN technology is now widely used, every IT professional should understand how it works and how to evaluate it.

CDN features  

A user from France can visit a Brazilian website and see its content in less than a second thanks to CDN. Parallel to the growth of CDNs, the market for streaming services began to take off in the 2000s. 

With streaming services, we can instantly have internet access to HD video when watching Netflix episodes or listening to high-bitrate music on Spotify thanks to the closeness of CDN servers.

Let’s look at two scenarios to better understand how CDN works: 

  • how the technology works from the user’s perspective 
  • how the technology works from the perspective of the acceleration service’s customer. 

User side

Assume you’re in San Francisco and visit github.io, which has a primary server in India. All static content will be downloaded from cdn.github.io, which will be situated in the United States, in response to your request.

However, how does the website determine which cache server should provide you with the information? The border gateway protocol (BGP) makes this possible. It sends numerous announcements to your ISP’s IP network with the point of presence cdn.github.io, from which the router selects the one that is nearest to you (with the lowest request/response latency). AnyCast technology works in a similar manner.

Customer side

All static material is uploaded to an object repository, which is given its own Domain Name System (DNS) domain name. In this method, the website’s name is linked to its digital address.

This is the name that will be used to refer to the HTML page that the user has requested. The client also can choose an origin domain (a source server with static data) from which the local CDN-server downloads cached files and sends them to the user on the first request, but does not apply to it after that because the material is already on the local server.

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When is it beneficial to use a CDN?

  • If you need to send static material to a big number of visitors who are far away from the origin server in a short amount of time
  • If you have a lot of weighty information on your website (high definition videos, audio files, and so on)
  • If you don’t want to spend money on network equipment upgrades. In many circumstances, putting most static information on edge servers is far less expensive than upgrading to new, more expensive network infrastructure.

Testing CDN

According to Evgenia Egorova, QA expert at NIX United, testing of the content delivery network can be done from two angles:

  • From the customer’s side. In this scenario, we examine how the original content is cached before sending it to the CDN server, as well as setting up caching rules, translations and domain creation.
  • From the user’s side. We check to see if the content is properly transmitted between servers. CDNs must do end-to-end testing, which involves validating the complete data chain from customer to end user.

Creating reports is an important aspect of CDN performance testing. Reports assist you in obtaining information about the traffic to your domains. They must not be overlooked.

Selecting Environment on the CDN allows you to choose the application environment:

  • Production will apply the selected properties to all created edge servers at once.
  • Staging performs local work with a specific domain (this is a separate testing item because the functionality for the environments is different). 

Edge server settings involve thousands of different rules, from creating your domain, adding a certificate to it, and configuring the rules, to manipulating the users themselves.   

Purge Function helps with deleting and freezing cached files from Edge servers.

Purge Action allows you to delete or freeze content on a cache server. The Delete option here will remove data from your edge server’s cache, and Invalidate will make content unavailable to the user until it is deleted or updated on the origin server.

Conclusion

CDN technology is in higher demand than ever before due to the constant weighting of content on the Internet. There are now no comparable alternatives for the quick transport of massive amounts of static data across the network anywhere in the world. As a result, knowing the fundamentals of CDN-server administration is essential for establishing a user-friendly website. 

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