Content delivery networks, or CDNs, are more important than ever for supporting the transmission of high-volume internet traffic. These networks of geographically distributed and interconnected servers improve the distribution of web applications and streaming media by reducing the distance content needs to travel to reach users, no matter where they're located.
Content delivery network services offer a number of advantages. One of the most significant is their ability to allow organizations of all sizes and vertical industries a way to use bandwidth more effectively, while reducing data center infrastructure and connectivity costs.
The CDN market includes dozens of vendors, ranging from those with a global presence to ones that specialize in a particular country or region. The market is expected to grow exponentially to more than $30 billion by 2022, according to some estimates.
Initially primarily used by media companies and software distributors, CDNs today are considered an essential tool. Where the first CDNs were focused on caching static content near the target user, today's content delivery network services offer a wide range of capabilities that include streaming content, security, analytics and more.
CDNs let organizations offload content delivery to third-party vendors and, thus, avoid having to build out costly infrastructure themselves. The use of CDNs allows even small companies to project a large image to customers and provide secure, responsive and fault-tolerant connectivity to their customer base.
How content delivery network services have evolved
While the services offered by CDNs have evolved over time, their fundamental purpose has not. CDNs are all about improving the end-user customer experience; they provide high data transfer rates, coupled with low latency, resulting in better end-user response time.
Early CDNs functioned as the network edge for their customers. In the late 1990s, when the first CDN was launched, content consisted of webpages, GIF and JPEG images. CDN servers stored static content and delivered that data to end users on behalf of the origin website. This not only got the content to the end user faster, but it did so without burdening the source company's data center and WAN infrastructure.
Using extensive research into the content delivery network market, TechTarget editors focused on 10 leading providers of shared global content delivery network services. Our research included data from TechTarget surveys and reports from research firms, including Gartner and Forrester.
As audio and video became popular web content, CDNs evolved to deliver that content, as well. And as organizations became more comfortable with having IT services provided off premises by third parties, CDNs evolved even further. They offered a variety of functions -- from application delivery controller services, such as load balancing, to application firewall and other content and network security services.
Today, you will find that CDNs differentiate themselves both by the types of services they offer and by the granularity and functionality of those individual offerings. For example, some vendors offer services focused on API management, where others offer advanced content security, digital rights management and geoblocking features. While all vendors offer caching services for static content, some have added sophisticated management features for purging and refreshing cached content.
How CDNs work and are deployed
The CDN functions as a generally transparent proxy for your services and web resources. Consumers are usually unaware they're using a CDN, because, once a company's web address is entered, sessions are automatically redirected to the specific CDN via the domain name system.
The CDN locates its content servers using a combination of its own dedicated points of presence and POPs run by other internet service providers. To provide the best response time, the CDN will usually interconnect its edges using dedicated, private lines, rather than via internet links.
At the CDN edge, the customer request is inspected and processed. In the most common use case, static web content will be checked for freshness and then delivered. If your company uses the CDN to store customer-facing data files, such as product catalogs or software updates, those will be fetched from the CDN storage servers and delivered. Video files stored by CDNs can be delivered and streamed directly to the customer without burdening the origin company's servers or the origin company's WAN.
While it's good to know what the CDN does, it's just as important to know from where it does it. CDNs are all about faster delivery. A big part of that is reducing latency, which requires the CDN server be geographically near the end user. Thus, one of the first questions you should ask any prospective CDN vendor should focus on details as to where the CDN has a presence.
What is driving the increase of CDN use?
CDN use has grown over the past several years, paced in large part by video, which has become a common website element and tool for many businesses. Not only does video require a lot of disk storage in comparison to traditional web objects -- such as a PDF -- video delivery places a significant demand on internet and WAN bandwidth.
Another important trend is the use of cloud-based applications and services. Years ago, few IT managers considered placing their key corporate data outside of their data centers, but now this strategy is accepted and embraced. As a result, some content delivery network services are beginning to compete with cloud providers, offering such services as video and data storage.
Additionally, by putting the processing and delivery burden on the CDN's IT infrastructure, the burden is similarly reduced at the company's own IT site. This could translate into lower demand on existing IT and WAN infrastructure, reducing a CDN customer's Capex and Opex costs.
Key features of content delivery network services
It's important to realize the beneficial ripple effect of CDN offload. The obvious benefit of offloading delivery is fewer servers are needed, which means less physical real estate and power and cooling are required.
All CDNs offer core functions, such as delivering static, dynamic and, usually, streaming and on-demand video. These services alone are often sufficient to justify using CDNs, as companies can ensure their end users will benefit from rapid response time.
Even within the core delivery function, there can be additional benefits of CDNs, as some CDN vendors offer image optimization and management services. These services can dynamically deliver images optimized for a specific device, whether it's a desktop computer, a mobile phone or some other gadget.
Many CDN vendors offer advanced security-related services, such as distributed denial-of-service (DDoS) protection, web application firewall (WAF) functionality and bot protection. CDN security offerings can reduce the load on on-premises security hardware, thus extending its lifetime.
Some CDN providers are looking at offering services for company branch offices as a natural extension of what they're doing now for individual users. Branch-office users need content that originates at the headquarters location and that can be stored at and delivered by the CDN. Similarly, the CDN can provide WAF and DDoS for the branch. The only difference is those functions reside at the CDN edge, rather than on an appliance in the branch office. Such a service reduces the required IT footprint in the branch and generally simplifies branch operation.
The chief benefit of CDNs is their ability to offload significant amounts of delivery from your data center to the CDN, thus reducing your data center footprint.