What is a CDN and What are Its Benefits

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As a website owner, you might have often heard of a CDN and how it can help improve your site speed and security. A large amount of online content today is delivered with the help of CDNs. This content includes html, js and stylesheets as well as images and videos. Large tech businesses also use cdn for content delivery.

A CDN has become essential for optimized and fast delivery of content and for a superior visitor experience. Companies like Netflix, Facebook and Amazon also use CDNs for delivering content. Netflix and Hulu rely on several AWS cloud computing resources including the AWS Cloudfront CDN to deliver video content to users worldwide.

What is a CDN?

A CDN or Content delivery Network is a group of geographically distributed servers that help speed up content delivery by bringing it closer to the users. However, the role of CDNs is not limited to just content delivery but with proper configurations, CDNs can also help mitigate attacks.

When a visitor visits a website, data from that website’s server travels across the internet to reach the user. If the user is located in the area where the website servers are located then fine. Otherwise, a person sitting in North America and visiting a website whose server is located in the Asia Pacific will experience a slower loading website.

CDNs help overcome this problem and keep cached copies of the data to load them from the nearest server to the visitor. The role of CDNs in the distribution of online content has grown a lot. Now, they form the backbone of online data delivery.

How does a CDN work?

A CDN is basically a network of interlinked servers whose purpose is to deliver content as fast and cheaply as possible. CDNs establish a point of presence (POP) or a group of CDN edge servers at various geographical locations. These CDNs place data centers in strategic locations across the globe to speed up data transfer and provide higher security.

For example, Cloudflare CDN has more than 250 points of presence across the globe and the AWS Cloudfront CDN has more than 600 globally dispersed points of presence. The CDN does not only deliver content faster but also protects against DDOS attacks and provides data encryption.

CDNs generally work on the principle of caching and cache the status content. What about the dynamic content? How do highly dynamic websites benefit from the use of CDN? CDNs also provide dynamic acceleration.

CDN Benefits

Caching Static Content

Static content means the content on a website that does not change too often. The content remains the same from user to user. For example, images, stylesheets, logos etc remain the same for users and do not change quite often. A website might change an image or update its logo in a year or several months. Since such data does not have to be modified processes or updated, such data can be stored easily on CDN servers.

Caching static content is easier since static content does not keep changing. So, the CDN servers can deliver the same content over and over to users. There is a set time till when the content will remain cached. Caching basically means temporarily storing static content on multiple servers across the network. So how does static caching work?

A visitor visits a website from a geographically remote location. He makes a first request for content.

The request is received by the origin server which sends a response to the user and at the same time also sends a copy of the response to the CDN Point of Presence (POP), which is in the proximity to the visitor’s location.

The closest CDN PoP stores a cached copy of the response.

The CDN PoP serves the cached content to the visitor on subsequent visits or to other visitors from the area visiting the website. Each time the response does not have to be sent from the origin server.

So, this is how caching works in the case of static content. Browsers also have the ability to cache content for a fixed time period. Browser caching of content also improves page loading times.

If the content is not cached by CDN and browsers, each request would be sent to the origin server in which case, geographically remote users would experience slower loading times.

Dynamic Content Acceleration through CDN

This was the case with static content. What about dynamic content or websites whose content changes more often? Can dynamic content also be cached like static content?

Dynamic content changes more often and can be different from user to user. Two users with accounts on Facebook do not see the same content in their feeds even if the look of the page is similar. Same is the case with chat messages, login status and weather reports which can change from user to user and region to region. The website generates this data for individual users according to their preferences.

Caching does not work well in the case of dynamic content since with every request the content changes. However, CDNs can still accelerate the delivery of dynamic content. This is done through dynamic acceleration where the CDN servers sitting between the client and the origin server speed up the delivery of dynamic content. In the case of dynamic content, the CDN servers need to connect with the origin server each time. However, since CDNs optimize the connection between themselves and the origin server, it still accelerates the process of delivery of dynamic content.

Dynamic content is generated with the help of scripts and these scripts can be stored in cache and used to generate and deliver dynamic content. So, the dynamic content does not have to be served from the origin server, which reduces the response times and accelerates the delivery of dynamic content. CDNs can also speed up the delivery of dynamic content through dynamic compression. In that case, the dynamic content is still being served from the origin server but the size of the files is much smaller which helps deliver them faster to the client’s device.

What are the benefits of using a CDN?

A CDN offers several important benefits to websites and web applications including speed and security. It can improve normal website functions which can help web apps deliver a superior user experience and maximize customer satisfaction. It is used for high speed content delivery and for real time streaming as well as multi-user scaling.

Here are some of the leading benefits of using a CDN for content distribution:

  • Improved website load times: The primary benefit of using a CDN to deliver content online is faster load times. When you deliver content through CDN, the visitors are served content from the nearest CDN servers which reduces page loading times. Faster loading websites experience lower bounce rates since they provide a superior user experience. Visitors can leave the pages that load slowly but will stick around on websites that load faster for longer. Since bounce rates decrease with the use of a CDN, the time visitors spend on your website increases.
  • Lower Bandwidth Costs: Hosting costs or bandwidth costs are among the primary expenses incurred by website owners. CDNs help reduce bandwidth costs through caching and other optimizations. It helps reduce the amount of data that a website must provide and helps reduce the consumption of bandwidth. This helps webmasters reduce their hosting related expenses.
  • Higher content availability: Sometimes, websites might experience a sudden spike in traffic. Too many visitors reaching the website at the same time or due to network hardware failures the normal working of a website might be interrupted. A website can crash in such a situation. However, CDNs can reduce the load on origin servers considerably. They can handle traffic spikes with much more ease compared to origin servers, because of their distributed nature. Moreover, if one cdn server fails, it can easily be replaced by another server which ensures that website service is not interrupted.
  • Higher website security: A CDN can provide several security features including DDoS mitigation and other security related optimization. DDoS attacks a large volume of fake traffic to web applications at once to bring them down. Several such attacks are carried out so subtly that they can be quite difficult to identify. However, CDNs can easily protect the origin servers against such DDoS (Distributed Denial of Service) attacks. CDNs distribute the load of traffic spike on several intermediary servers which prevents any impact on the origin server. Several CDNs offer extra security mechanisms and features to keep a web application secure from various forms of attacks. For example, if you are using Cloudflare, you can set the level of security you want. You can also serve users with a captcha for verification with Cloudflare. AWS Cloudfront CDN also provides encryption solutions apart from other default security controls.

In this way, there are several major advantages of using a CDN for your website’s content delivery. Apart from delivering static content on your blog through cdn urls, you can also use a CDN service for full website delivery. You can be assured of your website’s security against attacks and also of availability and speed. A CDN cannot replace web hosting. You will still need an origin server to host your website content. However, legacy hosting is not sufficient to meet the growing needs of web applications. CDNs help web applications with speed, security and availability and help maximize customer satisfaction.

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