A Content Delivery Network (“CDN”) is a network of proxy servers and data centres, specifically designed to provide high availability and performance for delivery of Internet content.  Initially mainly confined to media content delivery, their scope has expanded to other types of Internet content. They are frequently used by e-commerce vendors and media companies, who pay CDN operators for content delivery to the end-user.

In reality, CDN is an overall term covering many different types of content delivery services, ranging from the original video streaming and content download services to other services supporting internal and other client-facing services such as load balancing, automating CDN switching to optimise service levels and various levels of malware protection.

A CDN operator will co-locate their equipment with ISPs and pay other carriers for premium connections such as high-speed fibre.

They can be viewed as a delivery layer lying above that of the basic Internet.

A single CDN operates over one or more backbones, with nodes in dispersed geography. The number of nodes will vary from a relatively small number to several thousand nodes, each with several servers in remote Points of Presence.   Some dedicated private CDNs operate over a glocal network with a small number of local nodes for each location where service is required.

The main problem with a single CDN strategy is that of it being a single point of failure. If your CDN topology fails, then you cannot deliver, with the potential loss of income and damage to your business reputation.

To guard against this, many organisations opt for a multi-CDN environment to provide the benefits of improved uptime, reliability and speed.

The basic business rationale for a multi-CDN strategy is the increased demand from clients for fast and reliable streaming video, online gaming and item download. They demanded improved service levels for an excellent quality of experience (“QoE”) from their Internet service supplier, and it has become apparent that a multiple CDN strategy will provide benefits that will improve the QoE.

In the past multi-CDNs have been one primary CDN and a backup CDN used for when the primary fails for any reason. This means downtime when switching between the primary and backup CDN and certainly reduced service levels while switching. Today, most multi-CDN configurations are where all the CDNs are active, which allows load balancing between different routes providing improved service levels to the user.

In some more detail, the benefits include:

Reduced bandwidth cost

Properly optimised CDNs reduced the amount of data an origin server must deliver. This will generally reduce website hosting costs

Improved availability

A single CDN is a single point of failure, either through excessive traffic loads or failure, perhaps even a malware attack like a DDoS attack. Multiple CDNs will cope with hardware failures, excessive traffic and DDoS attacks better than a single CDN because of their distributed architecture.

Improved load times

Many users will terminate or click-through a website session if it takes too long to load. Complex sites with embedded video are particularly prone to bounce. By caching content closer to the user at a CDN node, load times can be reduced as can click-away rates, optimising the visitor’s experience.

Security

Security is a major concern for both operators and users. A CDN must be able to guard against a variety of malware threats, including data breaches, man-in-the-middle attacks and DDoS attacks.

At the very least it must use SSL/TLS security to provide that https:// feeling. SSL Certificates provide a level of security for websites and the origin server and if necessary intermediate servers at nodes must support SSL Certification.

In some cases, the CDN itself will have the added benefit of its own certification.   As an aside, stronger web security and website encryption improve Google search rankings.

A threat to most businesses is the inability to reach their servers during a DDoS attack. Initially individually directed from a single point, hackers now use botnets on multiple sites to increase the ferocity of their attacks.  A multiple CDN configuration can increase protection because of the sheer scale of the CDN itself.

Overall, a multiple CDN can provide increased security for hosted websites, benefitting the owner and user alike.

Management

Most CDN providers can supply analytic and tracking data as their usage scripts are used at the user websites. While this is a potential privacy issue related to behavioural targeting, it is being addressed right now and can be expected t be resolved quite soon.

Having said that, the information supplied as part of a multi-CDN environment can help a website owner optimise their SEO and backlink information to maximise their sales potential for online marketing sites. It can also assist an organisation optimise its node positioning to better service key market or office locations.

In comparison with a Single-CDN strategy, a multi-CDN strategy will provide cost, security and operational benefits.