CDN is abbreviated as a Content Delivery Network. A Content Delivery Network is a system of a distributed network (servers) which delivers your website pages and other website content to the user who visits your website. In other words, content delivery network refers to a geographically distributed set of server networks working together to provide fast delivery through the internet. It works based on the geo-location of the visitor in order to deliver the website content quickly. The content delivery network works in a way to provide the efficient, fast and secure delivery of content to website and internet services.
 
A CDN allows to quick transfer of information needed for HTML page on the internet while loading. It also used for JS (JavaScript) files, CSS Stylesheets, images and videos and other content in the particular website. It gets information from the origin server to display fastly.
 
Evolution of CDN
 
This type of service is efficient and effective in speeding the delivery of the content from your websites even when there is high traffic. It helps in the case of your website reach very high traffic and the number of visitor’s visits your website at the same time in the different location.
 
The number and closer the Content delivery network server fasten the deliverability of the server to the user. It provides large traffic protection to your website.
 
It is a geographically distributed network of proxy servers and their particular data centers. The main goal of the content delivery network is to distribute the service spatially relative to end visitor’s in order to provide high performance and all time availability of a website. It is a large portion of the internet and content all web documents and all downloadable objects, applications, streaming media properties.
 
A content delivery network is one of the layers in internet ecosystem. Owner of the content/ website such as media, e-commerce vendors pay for CDN operators to deliver their content to their users on all pages without any disturbances.
 
It is a transparent backbone of the internet responsible for a content delivery. We all are interacting with the content delivery network daily that without know that we are interacting because, most of all websites are integrated with CDN. Whether when watching YouTube videos, e-commerce site & other shopping sites, news site, and social media sites like Facebook, LinkedIn, Twitter, Quora etc.
 
Now lets us see how Content Delivery Network exactly works to delivery uninterruptable connection.
 

Working of CDN

 
Content Delivery Network works based on geographical locations. It scans the all contents in your website and makes a copy of your pages to the network of the servers that are dispersed at different locations and caches the content in your pages. It stores all information of the content in the form of cache. To minimize the distance between the user and your website server, where it stores data as a cache in multiple geographical locations. Whenever the visitor wants to visit your website the request has been sent to the nearest server. With the help of the CDN, your nearest server already cached the information of the content you are searching for. The CDN server automatically sends the request and redirect that requests to the closest to the user and the delivered cached content. The CDN server will also communicate with the original server / main server to deliver all information if not cached previously.
 
Content Delivery Network (CDN) reduces the response time and improves the loading speed of the web page. If there is less response time for loading means, automatically your site will rank in Search Engine Result Pages (SERP).
 

CDN Building Blocks:

 

PoPs

 
PoPs is abbreviated as Points of Presence. It is a strategically located data centers which are responsible for communication with users in their geographical vicinity. The main purpose of this is to reduce the round trip time by bringing the data to the user from the server. Content Delivery Network PoP consists enamours of caching servers.
 

Caching Servers

 
It is responsible for storage and delivery of the cached files from the main server. The main purpose of the caching server is to accelerate the page loading timing and to reduce the consumption of bandwidth. Each caching servers consists of multiple storage drives with the high amount of RAM resources in it.
 

HDD/SSD & RAM

 
Every PoP consists of numerous caching server to store the cached data. To store those large number of data a solid state hard disk drives like SSD & HDD or RAM (Random Access Memory) is needed. Among those three types of storage RAM is typically used to store the most frequently accesses data files.
 
CDN
 
The above image shows how the content delivery network servers are connected. The main server is also called as the original server. And the geographical server is mentioned as an edge server in the above image. The original server consists of all the website data. The edge server initially caches all the website data to serve the users. As mentioned in the image the edge server is connected to the device of the users. When a user request for a query, the edge server gives cached content to the users. Now you may have a question like what happens when there is a change made to the website or added new page/ information. The edge server requests to the original server whenever the change occurs in the website. There may be several numbers of edge server. The number of edge servers gives you a better performance and loading speed. And the edge server acting as an original server, so there is no chance of getting the server crashes when more number of user visits your site. Due to the edge server, the request and response time will reduce and a user can get the fastest service. If the nearest edge server is filled or currently handling with the maximum number of request means that request will passes to the next nearest edge server. As a result, again the waiting time is reduced and the server will not overloaded. The edge server having a queue to respond requests by users, if the queue fills it will allocate to other server to take care of the request. So the more number of CDN will increase the efficiency.
 
Content Delivery Network
 
For example, infozub.com website original server is in the United Kingdom and it having more number of edge servers in different countries like India, US, Canada, Australia and China etc. And assume that you are in Coimbatore and you are requesting for infozub.com site. The edge server is at New Delhi, Chennai, Bangalore, Mumbai etc. Coimbatore and Bangalore are nearest locations, so the request will be sent to Bangalore server. The Bangalore edge server already cached the data from the UK main server. So it will respond to your request from Bangalore. In case the queue is filled in Bangalore server and it will not able to respond to your query means it will search for the next nearest edge server location. Next, to Bangalore, the Chennai server is nearest to Coimbatore, so your request will be handled fully by Chennai Server.
 

Advantages of CDN:

 

  • Implementing the Content Delivery Network is efficient for the website which is popular to avoid crashes.
  • Boosts website performance
  • Reduce bandwidth Consumption
  • It reduces website loading speed/response time.
  • It increases the speed of the content delivery for visitors.
  • Increasing availability and scalability.
  • It minimizing errors so there is no need for extra additional expensive hardware’s.
  • Handles peak time loads.
  • Data Integrity and privacy are concerned.
  • High capacity infrastructure
  • Protects your website/ application from DDoS attacks
  • Blocks spammers, scrapers, and other bad bots
  • Distributed data centers
  • Secures your application/website
  • Usage analytics reports
  • Load balance between multiple users
  • Built-in version control

 

Types of Content Delivery Network

 
We can divide CDN’s into two types by its properties. They are
 
1. Push CDN
2. Pull CDN
 

Push CDN

 
In the Push Content delivery network, the data is distributed proactively to all edge server in your chosen locations. In other words, this push CDN will push all the static contents on your website to the edge server at first. Whenever the user/ visitor opens the particular page or request for the file like HTML, video, CSS, image etc, the content will load from the nearest server location (from the nearest edge server location). Push CDN cost is low than Pull. And it is more efficient in the long run.
 

Pull CDN

 
In the pulled content delivery network, when the user end sends the request for the page or any files, it pulls it from the nearest edge server location. Pull CDN is mostly used for small files like images in the website, JS – Javascript, HTML and CSS files. The pull CDN can help high traffic small download sites by keeping the popular data on CDN servers.
 

Evolution of CDN:

 
We are now in the third generation of CDN. The commercial Content delivery network is introduced in the 90’s.
 

1st CDN Generation:

 
The first generation of CDN is called as a static CDN. It is used to deliver static HTML files and small downloadable files. Its pricing is very expensive, and its follows origin push caching method. Its network topology is scattered.
 

2nd CDN Generation:

 
The second generation of CDN is called as a Dynamic CDN. It is used to deliver static and dynamic files. Its pricing is expensive, and its follows origin push caching method. Its network topology is consolidated.
 

3rd CDN Generation:

 
The second generation of CDN is called as a Multi-purpose CDN. It is used to deliver static and dynamic files including rich media and mobile. Its pricing is affordable, and its follows origin push caching method. Its network topology is highly consolidated.