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CDNs were created almost twenty years ago to address the challenge of pushing massive amounts of data rapidly to end users on the internet. Today, they have become the driving force behind website content delivery and continue to be researched and improved by academia and commercial developers.
The first Content Delivery Networks were built in the late 90s and these are still responsible for 15-30 percent of global internet traffic. Following that, the growth of broadband content and streaming of audio, video and associated data over the internet has seen more CDNs being developed. Broadly speaking, the evolution of CDNs can be categorized into four generations:
Pre-formation Period: Before the actual creation of CDNs, the technologies and infrastructure needed were being developed. This period was characterized by the rise of server farms, hierarchical caching, improvements in web servers and caching proxy deployment. Mirroring, caching and multihoming were also technologies that paved the way for the creation and growth of CDNs.
First Generation: The first iterations of CDNs focused primarily on dynamic and static content delivery, as these were the only two content types on the web. The principle mechanism then was the creation and the implementation of replicas, intelligent routing and edge computing methods. Apps and info were split across the servers.
Second generation: Next came CDNs which focused on streaming video and audio content or Video-on-Demand services like Netflix for users and news services. This generation also cleared a path for delivering website content to mobile users and saw the usage of P2P and cloud computing techniques.
Third generation: The third generation of CDNs is where we are now and is still evolving with new research and development. We can expect CDNs in the future to be increasingly modelled for community. This means that the systems will be driven by average users and regular individuals. Self-configuring is expected to be the new technological mechanism, as well as self-managing and autonomic content delivery. Quality of experience for end users is expected to be the primary driver going forward.
CDNs initially evolved to deal with extreme bandwidth pressures, as video streaming was growing in demand along with the number of cdn service providers. With connectivity advancements and new consumption trends in each generation, the pricing of CDN services dropped, allowing it to become a mass-market technology. And as cloud computing became widely adopted, CDNs have played a key role in all layers of business operations. They are key to models such as SaaS (Software as a service), IaaS (Infrastructure as a service), PaaS (Platform as a service) and BPaaS (Business Process as a service).