As frequent users of popular web services like Google the search engine, Facebook the social media network and eBay the eCommerce giant, you may address those web services as lightning-fast websites which loads the web page within milliseconds on your web browser. But to make it as fast as it is now, these web organizations have overcome many technical challenges which cause latency on web communication such as performance of the webserver, size of the web page content and the geographical distance between the web server and the visitor [1]. Latency has become crucial when it comes to web services that provide services to users around the world on a global scale. Web latency can be defined as the time delay which takes to load a web page on your web browser after typing the URL in the address bar of your web browser or clicking on a link to the desired web site [2]. 

In order to overcome the latency caused by the geographical distance between the web server and the visitor or in other words the number of hops that a data packet of web request should travel to obtain web page content from the server to the visitor’s end device, the modern web architectures include a Content Delivery Networking or CDN component which is designed to optimize the web content delivery by reducing the impact of the geographical distance factor for web communication. A CDN is simply a globally distributed and interconnected server group which caches (storing copies) the contents of origin web server such as images, videos, JavaScript, CSS files and serve those content to the requested visitors from the closest CDN server or also know as CDN PoP (Point of Presence) [3]. The following illustration briefly explains the role of a CDN on web communication. Even though a CDN is mainly responsible to provide fast web loading experience, the presence of the CDN is not directly visible to the web visitor, therefore a CDN can be called as the invisible backbone of modern World Wide Web.

Web communication without CDN and with CDN

Why CDN?

Being faster is not the only reason to adopt a CDN solution for a website, because CDN is able to prevent the webserver crashes, by distributing the heavy traffic load across multiple servers which are traditionally destined to the single-origin web server. However, the following reasons can be highlighted as the main reasons to implement a CDN for your website.

  • CDN increases the conversation rate of a website: Conversation rate is a web metric that defines the number of visitors who has performed the intended actions of the web owner [4]. If it’s an eCommerce site, the number of visitors who have bought a product or service offered by the website is represented by this number. Nowadays visitors tend to buy online because it is so fast and efficient. In that case, if the eCommerce website does not load fast and provide very poor user experience to the visitor, then the visitor will not be encouraged to purchase the products or services of that eCommerce venture. When a CDN is implemented, it enhances the web loading performance for every visitor and indirectly influences the growth of the conversation rate of the website.
  • CDN reduces the bounce rate of a website: If a website, does not load within a significant amount of time, visitors give up their intentions to check the further web pages inside the website after experiencing the poor performance of the first page and they simply bounce to another website to achieve their requirements. The number of visitors who leave the website after their first impression is indicated by the web bounce rate in the internet marketing sector [5]. The following graph reveals the findings of a research conducted by Pingdom that emphasizes the effect of load time to the bounce rate of an average website. According to the chart, the web load time should be less than 3s to achieve a lower bounce rate for a website.  This is another reason to use a CDN service to increase the load time of a website. 
Web Page Load Time vs Bounce Rate
Source: Pingdom.com [5]
  • CDN improves SEO rankings: Today, when a person wants to know about something or want to buy something, the very first thing he/she does is searching the internet about the term through a search engine like Google. The responsibility of a search engine is to provide the most useful online web resources on the search result which may cater to the requirement of the user. Based on above-mentioned reasons to use a CDN, web page load time clearly reflected in the visitor’s satisfaction of a particular website or the content inside it. Based on those factors, Major search engines like Google has defined the web page load time as an essential element of their search engine algorithm to rank a website/webpage on their web indexes [6]. As a result of that, if the site could not provide a better load time, the site links will not appear in the first positions in the search engine result for specific keywords. If the site links do not rank on the search engines likewise, the website loses a massive amount of visitor base from search engines. This is the main reason for modern web owners to concern about CDN implementation for their websites regardless of their scale.

How does a CDN Works?

The main goal of a CDN is to minimize the geographical distance between a web visitor and the web content serving location (Server). CDN service maintains a server network throughout the world which is capable to retain the cached versions of the origin web server content and distribute the cached content to the visitor from the closest cached server to visitor’s location based on his/her IP address [7].

The logic behind a CDN can be explained through the Telegram service by post offices. Before the telephone service is widely spread to rural areas, the only way to communicate between long-distance was the postal service.  Sometimes it took weeks to receive a mail from one city to a village which is located far away. As a result of that, people do not have a way to send urgent messages to their relations and friends who live far away from their location. To address this issue telegram was introduced to the post offices. That way, the sender can submit his message to the closest post office to his/her location and the post office will send the message to the post office closest to the receiver through the communication network established between post offices and deliver the message to the receiver via a postman within 1-2 days. The sender’s post office is can be assumed as the origin server and post office closest to the receiver is the CDN PoP in this scenario. 

However, the process of a typical CDN is much more complex and advanced than that. Because a CDN does not only deliver the content to a single receiver. Basically, it stores the content copies in its caches and delivers those to the next content requesters for a significant amount of time-based on the predefined cached content expiration time or trigger like a manual purge.

Modern CDN has broadened their horizons from the content delivery and they also offer security solution to websites such as DDOS protection, DNSec and also image / HTML compression to minimize the web page size to reduce load time to the visitor [8].

Who Should Use CDN?

Pretty much every website that targets the worldwide audience should use a CDN to increase its global presence in a productive manner. Having a CDN is a critical requirement for the following types of web services. 

  • eCommerce
  • Media/Publishing
  • Government
  • Online Gaming
  • Online Advertising

Which CDN Should You Use?

There are factors you should concern when you are selecting a CDN solution for your personal or organizational websites. Some of them are,

  • The availability of CDN PoP in the geographical regions that your targeted and widely using audience lives.
  • The ability and compatibility to easily set up and maintain the CDN for your web instances.
  • `The additional services that the CDN provides. Such as image optimization, DDOS protection, DNS hosting etc.
  • Your financial affordability to their service pricing plans.

The following table contains a feature comparison of the most popular CDN service providers in the current CDN marketplace such as Cloudflare, KeyCDN, Fastly, BunnyCDN etc.

CDN Comparison
Source: Official Websites of each CDN service

Wrapping Up

Approximately 8.8 million websites in the world wide web are using Content Delivery Networking (CDN) to optimize their web delivery at the moment [4]. CDN had a marketplace which is valued at around $9.24 Billion in 2018 [4]. This number is still growing and the need of CDN for websites is now critically discussing in the corporate ecosystem more than ever.

References

[1] D. Low, “10 Frustrating Reasons Why Your Website Speed Is Slow,” Bitcatcha, 16 August 2019. [Online]. Available: https://www.bitcatcha.com/blog/10-frustrating-reasons-why-your-website-speed-is-slow. [Accessed 20 August 2019].

[2] Imperva, “What is Network Latency,” Imperva, 2019. [Online]. Available: https://www.imperva.com/learn/performance/latency/. [Accessed 20 August 2019].

[3] G. Held, A Practicle Guide to Content Delivery Networks, New York: Auerbach Publishers, 2006.

[4] A. Skrba, “Content Delivery Network (CDN): How to Find the Best CDN Service for Your Website,” Firstsiteguide, 22 July 2019. [Online]. Available: https://firstsiteguide.com/cdn-guide/. [Accessed 25 August 2019].

[5] Pingdom, “Does Page Load Time Really Affect Bounce Rate?,” Pingdom, 18 January 2018. [Online]. Available: https://royal.pingdom.com/page-load-time-really-affect-bounce-rate/. [Accessed 20 August 2019].

[6] A. Singhal and M. Cutts, “Using site speed in web search ranking,” Google Webmaster Central Blog, 09 April 2010. [Online]. Available: https://webmasters.googleblog.com/2010/04/using-site-speed-in-web-search-ranking.html. [Accessed 05 August 2019].

[7] A. Vakali and G. Pallis, “Content delivery networks: status and trends,” IEEE Internet Computing , vol. 7, no. 6, pp. 68 – 74, 2013.

[8] Imperva, “What is a CDN,” Imperva, 2019. [Online]. Available: https://www.imperva.com/learn/performance/what-is-cdn-how-it-works/. [Accessed 23 August 2019].