What Is a CDN? Introduction to the Content Delivery Network

A content delivery network (CDN) is a geographically distributed network of servers that helps serve web content to internet users more efficiently. 

One of the biggest dilemmas faced by content delivery-based businesses is how to get internet content to website visitors anywhere in the world without long load times. 

Say you’re running a streaming platform. If a user makes requests from halfway around the world from where your content exists, the bandwidth consumption and load times might be unacceptably high. This could impact the viewers’ experience negatively. 

This is where a content delivery network comes in handy. By strategically distributing content on CDN servers around the world, the content is available to end-users from a nearby CDN server, rather than going from an origin server that could be on a different continent. 

Ultimately, it all saves time, money, energy and server resources. 

This article shows how content delivery networks function, what the basic functions look like and what the advantages are for businesses trading in content. 

How does a CDN handle requests?

Let’s say you are an internet user and want to load some static content, like a web page. This is the process a CDN will go through to deliver your content.

1. When a user in your geographic area requests data for the first time, the CDN transfers the data files from the original host web server. 
2. This data transmits via the edge server that is nearest to your device. 
3. The edge server caches a copy of the data. 
4. When the user requests the same content, the data transmits from the edge server rather than the origin host server. 

What do you need to know about CDN?

So, how does a CDN work? A CDN works by sending content data from an origin server, via internet exchange points where the CDN provider has a presence, to edge servers at points of presence that cache content for end-users to access. Let’s break down these terms. 

Origin server

As you may guess by the name, an origin server is a server that hosts the original version of the content that users might request. If you’re not using a CDN, all user requests go to this server. 

Since this is the primary server for your website content (static content), if all users required a response directly from it, the load on this server would be substantial. If the server were overloaded with requests, content availability could drop to zero. 

This would also mean that all website content stored on this server would only be available from one geographic location. This means that users located further away from the server would need to wait longer before their content request was satisfied. 

Without a CDN, the origin server is prone to long loading times, overload and DDoS attacks. 

Edge server

CDN edge servers are servers that are distributed around the world. They can receive and cache content from origin servers. 

An edge server sits at the edge of the network to be physically closer to the end-user. The shorter distance means that you need less time and bandwidth to send data from the server to the user. 

Edge servers connect different networks to allow fast and efficient data transfer. 

All this means that the user consuming the content can enjoy faster load times and a better experience on web pages and apps. 

The edge server can also help balance the traffic load on the origin server. This makes the network more resilient to sudden increases in traffic volume or cyberattacks. 

Internet exchange point

The internet is not actually one network, but rather a network of networks that all need to exchange data. 

Internet exchange points are a common feature in the internet infrastructure. It helps network operators, CDNs and internet providers connect their networks with one another. 

Like edge servers, these internet exchange points are on the edge of each network. Not only do they allow networks to communicate but also help shorten the path required to transmit data. 

This path optimization is crucial for CDNs since a presence in internet exchange points ensures efficient and speedy transmission of content by cutting out inefficient paths.

Point of presence

A point of presence (PoP) is a physical location where a company or organization has an edge server located. It can send, receive and cache data. 

In most cases, a point of presence is a data center that stores many servers. These might all be CDN edge servers that belong to a single organization, or a facility maintained by one organization that contains servers owned by many. 

The multiple locations of PoPs are chosen strategically to ensure that there is not too far a distance between any end-user and the nearest PoP. 

CDN service providers usually choose to keep their edge servers together in a data center. This means the servers can share security, environmental control resources, bandwidth and monitoring, which cuts down the overall hosting costs. 

Caching

Caching is the secret sauce that makes CDN services work so effectively. 

In general terms, cashing refers to the temporary storage of copied data. A cache is a temporary storage location for that data. 

In terms of CDNs, the edge CDN server acts as a cache that creates copies of content like images, HTML or Javascript files, and media files. Users access these copies instead of accessing the original version of the data on the origin server. 

This allows content to go from a server closer to the user. Moreover, the content is available on alternative servers if the host server is experiencing issues. 

What are the benefits of CDNs?

Now that you have a better understanding of what CDN is, how CDN works and how it affects website performance, let’s explore why a content delivery network is helpful. Here are the benefits of CDN services:

• Improved website loading speed
• Increased website security
• Reduced bandwidth usage 

Improved website loading speed

The modern internet is all about website speed. If web content doesn’t load instantaneously, users are likely to find another website to access the content they’re looking for. Lengthy load times can disrupt the normal website function and, in turn, cost money and harm rankings. 

If web traffic needs to fetch data from origin servers to provide web content, loading speed can be negatively affected. By using CDN services to keep your data cached in data centers that are geographically closer to users, you’re able to reduce load times significantly

Since users tend to abandon slowly loading websites, CDNs can help reduce bounce rates and increase the time spent on the site. A content delivery network is incredibly helpful if your business relies on a good user experience. 

Increased website security

Usually, when a server makes content available with traditional web hosting, anyone on the internet can see the original server’s IP address. This can facilitate distributed denial of service (DDoS) attacks and crash the website. 

Many providers that offer CDN services also offer the ability to proxy the IP address DNS A records of the server, so that it is not visible on the open internet. 

There’s also another way CDNs help protect your website against malicious attacks. Since website data is cached on a number of servers, a CDN carries out load balancing, which spreads the network traffic among the available servers. 

This helps manage the load of legitimate traffic at times of high volume. Moreover, it makes it harder for hackers to carry out DDoS attacks. DDoS attacks work by bombarding a server with more data requests than they can handle. However, if the load is balanced between multiple servers, your website is more resilient. 

Reduced bandwidth usage

When a user requests content from a website or an online application, the data that makes up such content must travel via physical pathways to the user’s device. However, the further these assets need to travel to their destination, the higher the bandwidth consumption is. This ultimately leads to higher bandwidth costs for companies. 

The internet community favors high-resolution video and images, which only compounds the problem with a higher data load. 

By cashing content data at network edge servers, a CDN can reduce bandwidth consumption by reducing the amount of data and distance required to satisfy the user’s request. The cached version of the site is retrieved instead of connecting to the origin server. 

Of course, CDN providers charge for their services. Can CDN reduce bandwidth costs so significantly that, on average, they outweigh the cost of paying for the service? Absolutely. 

Conclusion

To sum up, a content delivery network (CDN) is a globally distributed network of servers that make content distribution around the internet more efficient. By caching content in data centers around the world, CDN providers make sure that content is physically closer to users. 

By reducing bandwidth costs, website load times and server load, and by helping improve the overall end-user experience, a content delivery network assists businesses relying on great website performance. 

But who exactly is looking to use the services of a CDN provider? The use of a content delivery network can be handy for organizations in all kinds of sectors, including but not limited to:

• Media: News publications or streaming services delivering content (high-definition content) to thousands or millions of users across the planet 
• eCommerce: Online retailers who need to respond to high volumes of users during sales events without overloading servers 
• Banking: Financial institutions that need to move sensitive data quickly and securely
• Public sector: Governmental organizations that need to ensure that information and services are available quickly and reliably for citizens
• Online applications: Companies that offer SaaS services and online apps enjoyed by thousands of daily users

Should your organization use a content delivery network?