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What is a CDN and how do they work?

The internet uses the end-to-end principle: information moves from the hosts to the clients. When the internet started, this was to keep content delivery simple and easy. The growth of the internet meant that content delivery networks (CDN) became necessary – but what is a CDN? And how does it work?

The Beginning Of Content Delivery Networks (CDN)

As the number of internet users grew, a number of consequences became apparent. 

Bottlenecks were created, long waiting times ensued, and delays were experienced when content was accessed or requested by a large number of users around the globe. This can happen when a user is physically distant from a website’s host server, or when there are issues with transmission mediums and bandwidth. 

Considering that Google has revealed that the probability of a visitor bouncing from a website increase by 32% as page load time foe from 1 to 3 seconds, keeping websites fast is obviously a commercial priority. 

As a result, the infrastructure evolved to keep this principle moving forward. CDNs or content delivery networks were designed. The distance between a guest user’s and a host’s server was shortened. 

Nowadays, CDNs are a vital part of the Internet ecosystem. Its primary purpose is to deliver the information requested by a user quickly, improving site experience and performance. It is a network of proxy servers and data centres that deliver content with high performance and high availability to end-users. This is done by geographically distributing content from content owners to different proxy servers and data servers to reduce latency when a user requests it. Latency is the length of time it takes for content to be delivered to a user located in any part of the world.

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What is a CDN?

Since the 1990s, from the early stages of Internet use growth, CDNs have seen an upsurge in demand. Today, much of the internet depends on CDN operators for streaming services, downloads, web objects, social media, etc., from a website or mobile application. 

CDN nodes are spread out over multiple locations. This is done so that bandwidth costs are reduced, page loading is faster, and the reach of content has a broader range globally. 

Depending on the demand and the available infrastructure, servers and nodes of a CDN can be hundreds to tens of thousands of PoPs or points of presence. This means that when a user requests content, a server nearest to the user is chosen based on an algorithmic code that is used to optimize reach without increasing costs or sacrificing performance. 

For example, the less time in seconds from the user, the best available server with high performance, a server location that has the least hops, or even the cheapest option for a server. 

CDN operators also employ the use of caching servers which can store and deliver a large amount of cached data. These web caches may classify which information is stored based on popular content and on which servers have the most demand of the content requested. This enhances user experience by reducing server load, response times, and requirements on the bandwidth.

There are other types of CDNs which do not require the use of a commercial CDN operator. In a peer-to-peer network, content delivery networks happen through the clients providing the systems they use. The requirements for such a CDN are advantageous due to its low cost to the content distributor. Within this content-centric network setup, as more users access the content, the better the performance (e.g., the BitTorrent distribution system with torrent files containing metadata to be shared among peers).

A private CDN can also be set up that is independent of other servers, whose PoPs contain content available only for a particular person, group, or company. It can consist of a few caching servers or more, able to distribute up to petabytes of data. These private setups sometimes use public networks in addition to their own cache locations either for backup or to increase capacity. 

Who uses CDNs?

There are various content owners from media companies to e-traders who hire CDN operators. This enables end-users to access their content easier and faster. 

Using a CDN depends on the needs of the user or content provider. Most websites with a global reach and wide-ranging traffic use a CDN to handle the load. These websites tend to deliver services such as entertainment, health, government, e-commerce and trade, education, online gaming and advertising. From them, end users can watch or stream videos, videogames, trade and pay for products and services, download and exchange files, photos, music, and software, and so much more. 

On a deeper level, people can make intimate connections with one another—all because we can share our lives with whoever in real-time.

How does a CDN work?

When a user visits a website, this triggers a series of connections. First, through an Internet connection, the servers nearest to the user’s location are selected. The CDN then collects information on the website visited, including images and texts, that are saved in servers distributed in different geographic locations—the cached content. 

Once on the website, the user requests a specific webpage that is also in the CDN. Based on this request, the CDN will send this request from the user’s location to another server or servers which can deliver the content requested but is also nearest to the user. This will submit content that also has not been cached before any user action. The user’s device can then download and generate the delivered content. 

Essentially, if a website is hosted in the UK, your information does not have to travel the whole width of an ocean back and forth. It will just have to access the information from a server or servers located closest to your location. 

All of these happen in the blink of an eye. The user may never even know that the process takes various steps to give quick access to the desired content. On the other hand, access to CDN servers is accessible to all users – such as those who are located in China. 

Other websites can limit certain users from accessing some of their features while allowing others to avail premium features freely. Websites can even work without the internet, but this results in a page taking a long time to load.

Who are these CDN providers?

A lot of familiar names will pop when searching which CDN provider is the best. Some of these are Cloudflare, Fastly, KeyCDN, MetaCDN, StackPath, and Amazon CloudFront. These are just a few out there who are open for commercial and private content providers. 

All of them comes packaged with their own PoPs and physical servers and security mechanisms put in place to protect users and their content. In fact, a content provider can customize features that best suit their website. Some are free, and some require payment. A simple click in a browser can give one the resources and choices if one wished to used avail themselves of a commercial CDN operator.

Content Delivery Networks Today

Considerable advancements continue to improve user experience. Cached versions of web content are made available to millions of users at the same time because of CDN capability, all stored in various locations or PoPs to reach users located in every part of the globe. 

Once you upload information on the web, you are using CDNs too to store it—in their variety of servers. And this information, if you so choose, can also be viewed by other people, as many as it can reach. 

Knowing that the internet has become a mainstay in modern society, it is no surprise that enterprises are willing to capitalize on this growing industry. And users are quickly latching on, in turn shaping the demands for providers and infrastructure to catch up. 

All of that is just the basics of how the complex process of CDN makes our life in the modern world more accessible. A simple look into the technology that will shape our future in the years to come. 

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