What is a CDN (content delivery network)?
A CDN (content delivery network), also called a content distribution network, is a group of geographically distributed and interconnected servers. They provide cached internet content from a network location closest to a user to speed up its delivery.
The primary goal of a CDN is to improve web performance by reducing the time needed to send content and rich media to users.
CDN architecture is also designed to reduce network latency caused by hauling traffic over long distances and across several networks. Eliminating latency is important as more dynamic content, video and software as a service are delivered to an increasing number of mobile devices.
CDN providers house cached content in either their own network points of presence (POPs) or in third-party data centers. When a user requests content from a website, if the content is cached on a CDN, it redirects the request to the server nearest to the user and delivers the cached content from its location at the network edge. This process is invisible to the user.
Many organizations use CDNs to cache website content to meet their performance and security needs. The demand for CDN services is increasing as websites offer more streaming video, e-commerce and cloud applications, where high performance is key. Few CDNs have POPs in every country. As a result, organizations must use several CDN providers to ensure they meet the needs of their customers and users, wherever they are located.
Besides content caching and web delivery, CDN providers offer services that complement their core functionality and capitalize on their presence at the network edge. These include security services for distributed denial-of-service (DDoS) protection, web application firewalls (WAFs) and bot mitigation.
Other services offered include web and application performance and acceleration services, streaming video and broadcast media optimization, and digital rights management for video. Some CDN providers make their application program interfaces available to businesses to meet their unique needs.
How does a CDN work?
The process of accessing content cached on a CDN network edge is almost always transparent to the user. CDN management software dynamically calculates which server is located nearest to the user making the request and delivers content based on those calculations. CDN edge servers communicate with the content's origin server to deliver cached content and new content that has not been cached to the user.
Edge servers reduce the distance that content travels and the number of hops a data packet makes. The result is less packet loss, optimized bandwidth and faster performance. That minimizes timeouts, latency and jitter and improves the user experience. In the event of an internet attack or outage, content hosted on a CDN server remains available to some users.
Organizations buy services from CDN providers to deliver their content to users from the nearest geographic location. CDN providers either host content themselves or pay network operators and internet service providers to host CDN servers.
CDN providers also use load balancing and solid-state drives to help data reach users faster. They reduce file size using compression and special algorithms and are deploying machine learning and artificial intelligence to enable faster load and transmission times.
What are the uses of a CDN?
The main use of a CDN is to deliver content through a network of servers in a secure and efficient way. These networks improve the content security, performance and availability. They are also used to collect user analytics and tracking data on network traffic.
CDNs serve a range of content, including websites, mobile applications, streaming media and downloadable objects. Social media and search engine traffic go through CDNs.
Content-owning organizations use CDN services to accelerate the delivery of static and dynamic content, online gaming, mobile content and streaming video, as well as other specialized needs. Some examples of how CDNs are used include the following:
- An e-commerce organization uses one to deliver content at busy times of year when traffic spikes are likely.
- A bank uses a CDN to securely transfer sensitive data.
- A mobile application provider uses one of these networks to reduce load times and increase response times, improving mobile users' customer experience.
What are the benefits of a CDN?
CDNs provide several advantages, including the following:
- Efficiency. CDNs improve webpage loading times and reduce bounce rates. Both advantages keep users from abandoning a slow-loading site or e-commerce application.
- Security. CDNs enhance security with services such as DDoS mitigation, WAFs and bot mitigation.
- Availability. CDNs can handle more traffic and avoid network failures better than the origin server, increasing content availability.
- Optimization. These networks provide a diverse mix of performance and web content optimization services that complement cached site content.
- Resource and cost savings. CDNs reduce bandwidth consumption and costs.
What are examples of CDN platforms?
There are many CDNs available with a variety of features. Products include the following:
- Akamai Technologies Intelligent Edge
- Amazon CloudFront
- Verizon Edgecast
Some CDN providers, like Cloudflare and Verizon, market their platforms as CDNs with added services, like DDoS or WAFs. Other providers, such as ArvanCloud, offer CDN services as one of several broader cloud services, such as cloud security and managed domain name system.
History of CDNs
CDNs are an integral part of modern internet architecture. They were born from a need to maintain efficient website performance and still serve that purpose today.
Akamai launched the first CDN in 1998. The company's techniques serve as the foundation of today's CDNs. First-generation CDNs focused mostly on static content, such as software downloads, and audio and video streaming.
As cloud and mobile computing gained traction, second-generation CDN services evolved. They enabled the efficient delivery of more complex dynamic multimedia and web content. As internet use grew, the number of CDN providers multiplied, along with the services they offered.
Some CDN business models are based on usage-based pricing or pricing based on volume of content delivered. Others charge a flat rate for basic services or even provide them for free, with additional fees for performance and optimization services.