What Is a CDN And How To Implement It

What is a CDN?

A content delivery network or content distribution network (CDN) is a geographically distributed collection of proxy servers that make the delivery of web content faster by caching it closer to its end users. Data centers around the world temporarily store content, facilitating the accessibility by delivering the content from a nearby server. In 1990s, as the Internet started to become more and more popular among companies and regular people, the need for a better and faster performance resulted in the creation of CDNs. Today most of the web traffic is delivered through CDNs, including social media sites, streaming services, downloadable data such as software sites and documents, etc.

CDNs can also serve as protection against Distributed Denial of Service (DDOS) attacks, some of the most common malicious attacks.

How does a CDN work?

Content delivery networks (CDNs) operate by deploying points of presence (POPs) or clusters of CDN edge servers across various geographic locations. This distributed network leverages caching, dynamic acceleration, and edge logic computations to function effectively.

A content delivery network depends on three types of servers:

• Origin Servers: Within a connected delivery network, the origin server holds the original copy of a resource requested by a client. When content has to be updated, all the changes are made on the origin server. An origin server can be owned and managed by a content provider or hosted on third-party cloud infrastructure, such as Amazon AWS S3 or Google Cloud Storage. A distributed cloud private link enables the configuration of an origin server through a private link.
• Edge Servers: Typically owned or managed by the CDN hosting provider, edge servers, also known as "points of presence" (PoPs), are distributed across multiple geographical locations worldwide. These servers cache content copied from origin servers and deliver it to nearby users. When a user requests content from an origin server, they are redirected to the nearest edge server hosting a cached version of the content. If the cached content is outdated, the edge server retrieves the updated version from the origin server.
• DNS Servers: Domain Name System (DNS) servers manage and provide IP addresses for both origin and edge servers. When a client requests content from an origin server, DNS servers respond with the address of a paired edge server, enabling faster content delivery.

There are three main types of content that go through a CDN:

• Dynamic Content: Content created in real-time by the web server using common programming languages like PHP, Ruby, or Java.
• Static Content: Content that remains largely unchanged and doesn’t require on-the-fly generation, such as images, CSS files, and JavaScript.
• Streaming Content: Media files, such as videos or audio, that are played directly through a web browser's control interface.

The majority of CDN architectures are built around these essential components:

1. Delivery Nodes: The primary role of delivery nodes is to serve content to end users. These nodes are servers equipped with caches running content delivery applications and are typically placed as close to the user as possible.
   Content can be stored on delivery nodes in two ways:
   Push CDNs: Content is manually uploaded to delivery nodes. The main advantage is that content becomes immediately available to users. However, the drawback is that the content provider must actively update and "push" the content whenever changes are made.
   Pull CDNs: Delivery nodes automatically retrieve content from origin nodes based on cache expiration rules. The benefit is reduced effort for the content provider, as updates are automatic. The downside is slower delivery for the first request, as the speed matches that of a non-CDN setup. However, once the content is cached, subsequent users in the same region experience instant delivery from the node.
2. Storage Nodes: The main function of storage nodes is to store copies of the original data that’s being distributed to delivery nodes. These nodes can be organized in a hierarchical structure, enabling tiered caching for more efficient content distribution.
3. Origin Nodes: Origin nodes serve as the primary sources of content, facilitating its distribution across the entire network or within the content owner's infrastructure.
4. Control Node: The control node's main function is to host the management, routing, and monitoring components of a CDN.

CDN Benefits

Faster Website Load Times: CDNs enhance user experience by distributing content closer to website visitors, which reduces latency and accelerates page loading speeds.

Enhanced Website Security: Many CDNs offer security features, including protection against distributed denial of service (DDoS) attacks and enhancements to security certificates. These capabilities help safeguard websites from common cyber threats.

Reduced Bandwidth Costs: CDNs efficiently manage data transfer by caching content on edge servers and optimizing the delivery of resources. By reducing the amount of data fetched directly from the origin server, they minimize bandwidth consumption. This not only decreases hosting expenses for website owners but also helps prevent potential overage fees and enhances overall cost efficiency. Additionally, reduced data transfer improves server performance, freeing up resources to handle other critical tasks.

Enhanced Website Security: CDNs often include advanced security features to protect websites from common threats. These may include mitigation of distributed denial of service (DDoS) attacks, ensuring consistent availability during malicious traffic surges. Additionally, CDNs can enhance security certificates and implement features such as web application firewalls (WAFs) and bot management. These measures safeguard websites against a broad range of malicious activities, reinforcing overall cybersecurity.

Increased Content Availability and Redundancy: CDNs enhance content delivery by efficiently managing high traffic volumes and offering robust failover mechanisms. Their distributed architecture ensures content remains accessible even during hardware failures or unexpected surges in demand. By balancing loads across multiple servers, CDNs improve website reliability, minimize downtime, and provide users with consistent access to content.

Many of the benefits provided by CDNs can positively impact a website’s performance on search engine result pages (SERPs). While there are no guarantees of direct improvements in rankings, optimizing your web presence through a CDN can enhance factors that influence SEO.
Here’s how:

• Faster Page Load Times: By distributing content across servers in various geographic locations, CDNs reduce the physical distance between users and your web host. This results in quicker load times and lower latency, which improves user experience—a critical factor for search engine algorithms that prioritize fast-loading sites.
• Expanded Global Reach: The extensive network of CDN servers worldwide enhances user experience by providing faster access to content for users in different regions. This global presence is particularly beneficial for sites with an international audience, as it can boost rankings in local search results by improving content accessibility.
• Enhanced Website Availability: CDNs distribute traffic across multiple servers, preventing server overload and minimizing downtime. A consistently accessible website ensures uninterrupted visibility for users and search engines, helping maintain or improve rankings.
• Optimized Mobile Experience: CDNs are designed to deliver content efficiently to mobile devices, ensuring websites load quickly on smartphones and tablets. Given the growing emphasis on mobile-first indexing and optimization by search engines, leveraging a CDN can help improve your website’s mobile performance and search engine rankings.

Implementation of a CDN

Implementing a CDN involves setting up the service and configuring your website to work seamlessly with it. Here’s a simplified step-by-step guide:

1. Choose a CDN Provider: Start by researching and selecting a CDN provider that fits your needs, considering factors like budget, performance, features, and customer support. Popular providers include Cloudflare, AWS CloudFront, and Akamai.
2. Sign Up and Configure the CDN Account: Create an account with your chosen provider. During the setup process, you'll often need to specify your website’s domain and choose how the CDN should interact with your content (e.g., caching settings, security options).
3. Update DNS Settings: Most CDNs require you to redirect your website’s traffic through their network. To do this, update your domain’s DNS settings to point to the CDN’s servers. This is usually done by changing the nameservers or adding specific DNS records provided by the CDN.
4. Configure Your Origin Server: Ensure your origin server (where your website’s primary files are stored) is properly set up to work with the CDN. This might include enabling HTTPS, ensuring your site has a valid SSL certificate, and setting appropriate cache-control headers.
5. Test the CDN Integration: After setting up the CDN, test your website to ensure everything is functioning as expected. Check page load times, image delivery, and content accessibility from different locations to confirm the CDN is working effectively.
6. Optimize CDN Settings: Fine-tune caching rules, security settings, and compression options within the CDN dashboard to maximize performance. For example, configure caching policies to ensure static content (like images and CSS files) is stored on edge servers for faster delivery.
7. Monitor Performance: Use the analytics tools provided by your CDN to track performance improvements, bandwidth savings, and any issues. Adjust settings as needed to keep your site running optimally.
8. Regular Maintenance: Periodically review your CDN configuration and update it to align with changes in your website or business requirements. This includes purging outdated cache files and updating security protocols.