Content Delivery Networks (CDNs)
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An introduction to content delivery networks and how they improve customer satisfaction by optimizing website and mobile app performance.
Table of Contents
- What is a content delivery network (CDN)?
- Benefits of a CDN
- How it works
- Networks
- Services
- Pricing
- CDN for websites
- Providers
- Hosting
- Open source CDN
- Storage
- Tutorials
- CDNs and IBM Cloud
What is a content delivery network (CDN)?
A content delivery network (CDN) is a network of geographically dispersed servers that enables faster web performance by locating copies of web content closer to end users or facilitating delivery of dynamic content (e.g., live video feeds).
Each CDN server is located on what is called the network edge—closer to end users than the host server, which is where the web site originates. For this reason, CDN servers are often called edge servers. Each CDN server stores or caches copies of a subset of the web content—HTML files, images, audio, video, applications—from the host server. By reducing the distance between this content and end users, the CDN helps the website publisher provide faster performance for its users and control its own bandwidth consumption and costs.
Organizations typically purchase CDN services from CDN providers, which maintain their own server networks.
In the video "What is a Content Delivery Network (CDN)," Chief Architect Ryan Sumner goes through a scenario where a CDN helps make the website load time faster for globally distributed users:
What is a Content Delivery Network (CDN)?
For a closer look at cloud computing and edge networks, you may want to read the blog posts "Cloud at the Edge" and "Rounding out the Edges."
Benefits of a CDN
CDNs provide the following benefits:
- Akamai
- MaxDCN
- Incapsula
- Rackspace
- Cloudflare
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In the tutorial "Accelerate delivery of static files using a CDN," you'll practice how to upload files to a Cloud Object Storage bucket and then make content globally available with a CDN.
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Similarly, you can manage your data stored in IBM Cloud Object Storage via CIS's Resolve Override with COS capability.
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'How to: Use a CDN with an Express web application" demonstrates the benefits of a CDN and teaches you how to use an Express JS application as a caching mechanism
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Lastly, the "How IBM Cloud Internet Services optimizes performance" tutorial illustrates how to optimize the performance of your web services and applications.
- All topics
- Analytics
- Artificial intelligence
- Cloud
- Compute
- Data science
- Database
- DevOps
- Disaster recovery
- Hosting
- Integration
- Management
- Migration
- Mobile
- Networking
- Open source
- Security
- Storage
How it works
As previously noted, a CDN helps a web publisher deliver faster, higher-quality performance for end users by delivering content from servers that are closer to users than the website's origin server.
For example, suppose your website is based in the U.K. If someone from the U.S. accesses your site, the CDN serves that user from an edge server in the U.S., closer to the user, instead of from your U.K.-based origin server for the website. The result is faster content loading, faster web application performance, and improved user satisfaction.
Networks
More than half of all web traffic is served over CDNs, and that percentage continues to grow as businesses expand their global reach and offer more varied content types. These networks move content closer to end users so that the content may be delivered faster and with less latency. CDNs also distribute traffic loads so that no single server is overloaded with traffic requests. Gaming companies, cloud application creators, live-streaming and on-demand media, e-commerce sites with a global reach—as digital consumption needs grow, content owners rely on these networks to better serve their end users.
For a full overview of networking, see "Networking: A Complete Guide."
Services
A CDN primarily offers improved web content delivery, but CDN providers offer additional services that complement serving content.
Security services
CDNs offer security services that guard data centers and websites against distributed denial of service (DDoS), man-in-the-middle (MITM), and other types of attacks.
In a DDoS attack, the attackers try to overwhelm a site with more traffic than it can manage, with the objective of disrupting or degrading service. CDNs use analytics and automation to monitor for these attacks and respond by limiting request rates (the number of information requests an HTTP can make in a specified time period).
For more info on DDoS attacks, check out our video, "What is a DDoS Attack?"
Watch the videoIn a MITM attack, the attacker tries to intercept or alter the communication between the origin server, CDN servers, and website users. MITM attacks can occur at a number of places in a network, but CDNs help mitigate MITM attacks by adopting Secure Sockets Layer (SSL) and Transport Layer Security (TLS), protocols to secure communications between the CDN and website origin server, as well as the CDN and ISP.
Private CDNs
If you work with a CDN, you'll most likely share network resources with other CDN customers. However, some CDNs now offer private CDNs, which provide the customer with their own dedicated CDN resources. A private CDN might appeal to an organization that has strict security needs, specific geographic requirements, or simply wants its own dedicated edge servers that are highly available and won't suffer any latency issues.
Analytics
CDNs may offer analytics for monitoring website traffic and gathering metrics about visitors to a site. The objective is to track user behavior. With that information, website and web application creators can optimize content for users, improve site service, and target marketing efforts to specific user personas.
Pricing
Every CDN provider maintains its own pricing structure. Most charge a monthly fee based on gigabytes of data transferred from the edge servers to end users. Rates vary based on the region of destination (the region where your cached content is hosted and accessed by users). Providers also have different policies for storage; some charge storage fees while others do not.
Major CDN providers post pricing on their websites. For most providers, the per-gigabyte rate decreases as the total gigabytes of data transferred increases. Leading CDN providers also charge their customers only for the bandwidth used each month so that billing reflects actual use of the service.
Several providers even offer free levels of service. What is included in that free level of service varies widely by provider. Free and paid levels of service come with specific service level agreements (SLAs). Leading CDN providers tend to offer 99.9% of uptime to customers.
Before choosing a CDN provider, understand its pricing structure and SLAs. Since most providers charge based on actual bandwidth used, estimate usage before choosing a service to gain a general idea of what monthly costs will be. There are CDN pricing calculators online that help you compare pricing among top providers based on bandwidth estimates and bandwidth use by geographical region.
CDN for websites
Not every website publisher needs a CDN. A local school district's website, for example, may not need a CDN because most users will access the site from a nearby location.
But if you've a media-rich website, a geographically dispersed group of users, or mission-critical content that requires fast delivery, a CDN may be your best option.
Providers
The proliferation of CDN providers has been spurred by an increase in content types and devices used to access that content. Some of the top providers include the following:
When choosing a CDN provider, consider the size and distribution of its network, how well its server locations (called points of presence, or PoPs) map to the locations of your site users, customer support availability, pricing, and service level agreements (SLAs). Also, consider if the provider offers any additional services that would be helpful to your organization, such as added security and analytics services.
Hosting
CDN hosting describes the networked servers of a CDN provider that host selected web content from a website. While website hosting typically refers to only one server, CDN hosting includes many servers networked together. CDN hosting augments website hosting by caching content in network servers that are geographically closer to website users. This differs from a web server, which hosts your full site on the origin server. CDN hosting can, therefore, deliver content to users faster than the website's origin server.
Open source CDN
Not every organization can justify the cost of working with a CDN. Open source CDNs provide a less costly, although more time- and labor-intensive, option. With open source CDNs, you can link to libraries of content, such as CSS or JavaScript frameworks. Open source CDNs host elements of website infrastructure on CDN servers. Website content managers can access that content for free. Open source CDNs do not host your website's original content. However, they can improve content delivery by moving common web structural elements used by your site closer to your end users.
Storage
For website operators with robust content storage needs, CDN providers offer storage clusters that integrate with their network of edge servers. Website operators may want this storage capability if they serve large static files, such as videos or installation files. By storing these files closer to the end user, CDN storage delivers better service and faster downloads. These storage options also relieve the traffic burden on the origin server by decreasing load requests and routing those requests to CDN edge servers instead.
Learn more about how you can leverage Cloud Object Storage across all IBM CDN offerings.
Tutorials
If you're ready to learn more about using CDNs, try one of these tutorials:
CDNs and IBM Cloud
IBM offers CDNs in two flavors: IBM Content Delivery Network (CDN) and IBM Cloud Internet Services (CIS).
The IBM CDN, delivered over the Akamai network, allows your users to experience faster load times for web content and applications. It automatically scales your service as needed and uses pay-as-you-go pricing. Beyond meeting content demand, the IBM CDN also protects your website and web applications from attacks by adding an additional protective layer between your users and your infrastructure.
IBM Cloud Internet Services, delivered through Cloudflare, includes a set of edge network services to help you improve the performance of your web services and applications by leveraging three major features: Global Load Balancing and Content Optimization through Page Rules and Caching (CDN), which ensures every page renders as quickly and efficiently as possible. By protecting your origin servers from spammers, bots, and malicious crawlers, you can protect your origin's resources for your application's performance, which improves your customer experience.
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