By Steve Milmore, Director Corporate Communications at Limelight
March 9, 2021
Redundancy, the ability to scale to meet large traffic demands and expand globally have never been more important for fast growing content publishers. One solution is to implement a multi-CDN strategy.
A Content Delivery Network is a system of geographically dispersed servers that facilitates the delivery of digital content with high performance and high availability. The idea behind a CDN is to move content much closer to end users. Instead of centralizing digital content (web applications, web objects, files, downloadable media and streaming media) on a relatively small number of servers, the content is cached across many servers distributed around the globe. End-users now retrieve the content they’re looking for from the closest CDN edge server, rather than going all the way back to the origin to retrieve it. A CDN can also instantly create a TV broadcast-quality experience, while converting live streams on-the-fly into the right device formats. This results in much better performance (lower latency) for your customers. It also avoids overloading your origin and allows your audience to scale.
There are several reasons to consider a multi-CDN strategy:
Availability: While an outage may not rise to the level of global notoriety, it’s likely just as devastating for your business. As the Internet has become more critical to every aspect of business, minutes of downtime can impact your bottom line and damage customer relationships. Multi-CDN can minimize single points of failure by providing alternate delivery options in the event of an outage.
Performance: It’s unlikely that any single CDN delivers the best performance for all traffic types, in all regions, all of the time. By intelligently balancing your content delivery needs across multiple CDN providers, you can mitigate the impact the performance glitches of specific providers, in specific regions, for specific traffic types.
Capacity: Large-scale content delivery events may create choke points in individual CDN providers or in certain locations. Multi-CDN alleviates these bottlenecks by distributing load amongst multiple CDNs. For large live events such as the World Cup, rapid scaling is a critical function of CDNs. If a match is tied near the end of regulation time, there are usually massive spikes with fans logging in to watch the final minutes.
Security: Having multiple CDN providers allows you minimize exposure, or to bypass compromised CDNs altogether, in the event of a cyberattack.
In many situations multi-CDN can be beneficial, but how does one deploy multiple CDNs, and what factors should be considered in determining the best method for your particular application?
DNS: The Domain Name System (DNS) is a naming system for the Internet. However, the equipment running the Internet doesn’t understand domain names – it operates using IP addresses. The translation from domain name into IP address is performed by DNS. DNS is one of the most prevalent methods of switching between different CDNs in a multi-CDN environment.
Static: The most basic method of incorporating multiple CDNs is by modifying DNS entries. This method can be used in an active-standby configuration. For example, if one CDN fails the DNS entry is modified so that all requests are redirected to another CDN. Using this method, different policies can be enforced by mapping different hostnames to different CDNs.
Weighted Round Robin: The weighted round robin approach allows you to apply a different ranking to each CDN to indicate CDN preference. Weights or ratios can be based on criteria you determine most important for your business, e.g. cost, performance, ISP connectivity, etc.
Geolocation: In the Geolocation case, traffic is distributed between CDNs based on the end user’s location. This allows you to favor specific CDNs based on where traffic originates.
Performance: Performance-based load balancing takes into account current network conditions to achieve the best theoretical performance. This approach involves measuring network conditions and considering this data when making balancing decisions.
Multi-CDN has some compelling benefits but it is not necessarily for everyone. Ask yourself these questions when considering if a multi-CDN strategy is right for you: Can you afford minutes, or hours of downtime? Do you have traffic spikes that could be alleviated with an overflow capability to other CDNs? Are you digital content delivery needs performance-sensitive? Is your audience distributed across the globe? If your answer is yes to these questions, multi-CDN may be most beneficial to your organization.
Once you have determined that adding a CDN to your content delivery environment makes sense, the next question becomes which CDN partner to select. Here are some important factors to consider:
Geographic coverage: Important questions to consider: where are your users located? Where are you looking to expand? Look for a CDN that has a presence in the regions or countries where most of your users are located. When considering your global traffic distribution, it’s also important to think about future growth. If you expect to see increased traffic coming from emerging markets like India for example, factor that into your decision now to avoid having to renegotiate your CDN contract or prematurely move CDN providers. Look for a CDN that has a presence in places where most of your current and future users are located.
Performance metrics: This may sound obvious, but the best place to start is by considering what is most important to your customers’ experience. In this case important metrics for video delivery might include rebuffer rate, bit rate and startup time.
Performance measurement: There are several performance monitoring tools commercially available, however in many cases results can be misleading. The best approach to evaluate performance is to do a trial or proof of concept with one or more CDNs, using your actual workload in the geographical regions that are most important to you.
Service and support: Things sometimes go wrong or you may want to tap a technology expert. At times like this excellent support can make all the difference. Consider how important it is for you to have access to live customer support. Will that support be available outside of business hours? What kind of support is offered in your region? Is the support free or is there a premium charged for this service? If you deliver live events what relevant experience does the CDN partner have and are they willing to participate on a bridge before or during the event? Is the CDN vendor able to assist with onboarding or migrating from another CDN?
The bottom line: Using multiple CDNs to deliver these digital content experiences promises even greater levels of availability and performance. By leveraging the right combination of providers, enterprises you can simultaneously improve end user quality of experience while lowering costs. See Limelight’s detailed guide 5 Things You Need to Know About Implementing a Multi-CDN Strategy for more information on this topic.