A content delivery network (CDN) is a set of interconnected servers that cache content across data centers to provide high performance for all users, regardless of their distance from the server where the site or app is hosted. However, large organizations usually require more than one CDN to deliver content to their large customer base. This is referred to as a multi-CDN strategy. Read on to understand the components, benefits, and limitations of a multi-CDN strategy, and to discover how to implement multi-CDN for your business.
What Is Multi-CDN?
Multi-CDN, or multi content delivery network, is a strategy where a business uses more than one CDN to deliver content to users. The business splits traffic between delivery networks: some users receive content from one CDN provider, and other users from another.
Why would this be necessary? Let’s dive in and find out the benefits that a multi-CDN strategy affords businesses.
Increased Fault Tolerance
Delivery networks can go off-grid due to mechanical outages or cyber attacks. When this happens, a multi-CDN strategy redistributes traffic to other functioning CDNs, ensuring the continuity of the delivery loop. A multi-CDN approach is therefore important for organizations where outages can be disastrous, like in the financial and healthcare industries where downtime is not a viable option. All businesses benefit from preventing downtime, since this boosts the dependability of their business and improves customer experience.
Risk-Free Coverage Expansion
CDNs should have points of presence (PoPs) close to end users. This is a challenge when users are spread across sparsely populated regions, exist in specific local markets, or are truly global. The multi-CDN approach is useful in these situations. For example, if your business has clients in Bulgaria, Bahrain, and Turkey, you should select CDNs that collectively have CDNs in these countries. It may be challenging to find a single CDN provider with PoP in all three of those locations, but by working with multiple CDN providers you can be assured of coverage in all relevant markets.
If your organization needs to expand to a new region and test the market, you can add a new CDN provider and buy additional traffic solely for this exact region, without disturbing your existing setup. In the following image, the left map shows a business with three local US markets and a single CDN provider in those regions. On the right, we see that the business expanded nationwide and added two CDN providers for enhanced nationwide coverage.
Note that CDN A could provide coverage across the US, but the addition of CDN B and CDN C brings content closer to more users, improving performance across both new and existing markets.
Because network quality can vary significantly by region, relying on a single CDN can result in inconsistent user experiences. Such disparities can have negative knock-on effects on businesses in regions where performance lags. To mitigate this risk, a multi-CDN strategy is highly recommended. By employing multiple providers optimized for specific regions, you ensure that users across the globe benefit from the best possible CDN performance available in their area.
Pricing differs across CDN providers. Imagine choosing between two companies: One offers a reasonable CDN price in America and a very high price in Europe, while the other provides the opposite. A multi-CDN approach enables you to allocate traffic to the CDN that offers the most competitive pricing for each region and optimize your operational expenses.
The contract agreements of CDN providers are not set in stone; they change over time. Depending on one provider can result in vendor lock-in, forcing you to agree to unfavorable terms because the cost of switching to a different vendor is so high. A multi-CDN approach protects you by giving you an array of CDN providers that you can switch between with ease should you become subject to unfavorable terms with one provider in the future.
It is easy to think that the multi-CDN approach is simply a fusion of several CDN providers, but in fact the picture isn’t quite so simple. CDN providers are one component, with the load balancing tool being the second component. Let us take a look at these two in more depth.
CDN providers strategically cache content across globally distributed servers, ensuring swift content delivery to end-users, regardless of their location. CDN providers can do this via PoPs, high-capacity data routes, and other specialized functionalities, thereby sharply reducing the load on origin servers.
In multi-CDN, a load-balancing tool delivers content via the optimal route. You can distribute traffic between your CDN providers in two ways: via DNS or dedicated solutions. Let’s take a look at these two.
DNS Traffic Distribution
Traffic routing in multi-CDN is primarily implemented through DNS, which maps domain names to IP addresses. The local DNS server queries and caches the response from authoritative servers for a specific time frame known as time-to-live (TTL.)
You can balance CDN workloads by using authoritative DNS servers to route traffic to the best CDN provider for each region. The server is configured to determine the most efficient CDN based on metrics such as performance and availability. There are two main types of DNS traffic distribution: basic and advanced.
This approach is the simplest of the two options. It involves routing traffic, without preconfigured rules, to the established domain. For example, imagine the music streaming service www.streammusic.com has two main types of content, songs and album covers, which are stored on different origin servers and accessed by songs.streammusic.com and covers.streammusic.com, respectively. You can configure songs.streammusic.com to route to a CDN that specializes in audio streaming for delivering music tracks, and covers.streammusic.com to a CDN optimized for delivering image files for album covers.
Although basic DNS load balancing provides complete control over traffic direction, it requires active monitoring and manual adjustments, particularly during CDN outages.
This enhanced version of DNS-based distribution takes preconfigured routing rules—load balancing—into consideration. It automatically directs traffic based on established rules, such as Weighted Round Robin or the geographical proximity of the server.
For example, advanced DNS load balancing can route 60% of your traffic to CDN A and 40% to CDN B, if those are the conditions you set in your DNS records. Although this approach allows the even distribution of traffic between CDNs, you do not have absolute control over traffic routing.
Alternatively, the routing can be location-based. In this approach, users are served content by the servers closest to their location. This is done via GeoDNS and involves configuring routing rules such as autonomous system number (ASN), country, region, or exact location. A multinational e-commerce website could direct traffic from Europe to servers in the European region, and traffic from North America to servers in North America, to ensure faster loading times.
Dedicated Load Balancing Solutions
Dedicated load balancing distributes traffic based on real-time metrics, like network latency, provided by monitoring processes. This approach responds to network changes more rapidly than the previously mentioned DNS-based methods.
For instance, consider a video streaming company using a dedicated load balancer. Should CDN A encounter high traffic congestion, the load balancer intuitively redirects new user requests to CDN B, which currently has available capacity and, consequently, reduced latency.
As we’ve discussed, a multi-CDN strategy requires you to select more than one CDN provider. Let’s look at how to select your providers to ensure you reap the full benefits that multi-CDN has to offer.
Determine your specific needs and objectives for implementing a multi-CDN setup. Consider factors such as performance, fault tolerance, geographic coverage, cost optimization, content delivery requirements, user experience, and resilience against DDoS attacks.
Research and evaluate different CDN providers based on their performance, geographic coverage, pricing, features, support, and integration capabilities. Choose multiple CDN providers that best align with your requirements and provide relevant, complementary services.
You’ll want to focus on providers that address your specific needs. For example, if you’re primarily looking to optimize geographic coverage, pick providers with points of presence that together cover your complete geographic market. If you’re trying to improve fault tolerance at a low cost, you might pick one provider that offers a well-rounded package with features that suit your business, and a second provider offering a cheap, basic service.
The load balancing approach employed by the multiple CDNs can significantly influence the performance, reliability and cost-effectiveness of your multi-CDN strategy. Your specific requirements should inform the distribution method, whether static DNS, dynamic DNS, or dedicated load balancing.
Evaluating the success of your multi-CDN strategy requires thorough performance, cost, and effectiveness analysis. To optimize monitoring and performance analysis:
- Always request the raw logs from your CDN providers to ensure you can assess performance properly.
- Ensure that the same metrics are being measured for each network so that they can be accurately compared. Gather reports for identical timeframes and confirm that CDN operation data is comparable, because different providers may offer different metrics.
- Standardize HTTP headers added to requests and responses by CDN servers to simplify data parsing.
- Opt in to detailed statistics if your provider offers them, even at a cost. These provide in-depth information and open up more avenues for network performance analysis.
Regularly Review and Optimize
While multi-CDN offers numerous advantages, it is mostly beneficial for large-scale organizations with global reach and high traffic. It may not be financially viable for small-scale deployment because of its high setup and running costs. Multi-CDN implementation may have additional limitations.
Your chosen CDNs have diverse features and are connected via APIs. Managing this architecture typically requires considerable technical expertise. You may even need to allocate an entire team exclusively for monitoring and maintenance, which increases overhead.
To gain competitive advantage, CDN providers serve and load-balance in unique ways. This leads to an explosion of features that must be carefully streamlined and configured by an expert. Otherwise, the organization will not reap any of the benefits of implementing the multi-CDN.
The costs of implementing a multi-CDN approach are high, requiring both additional investment in CDN providers and increasing operational costs. So, it is important to carefully evaluate the gains of implementing a multi-CDN approach against its financial demands. Usually, this limits the appeal of the approach to large, global organizations.
Adopting a multi-CDN strategy can enhance content delivery and boost customer experiences. To reap these benefits, it’s critical to select your CDN providers carefully. Gcore’s CDN offers more than 150 points of presence, with outstanding coverage in Latin America, Africa, and Europe. Our team will craft a tailor-made solution developed specifically for your needs, leveraging Gcore’s cutting-edge technology stack and smart asset optimization, offering you exceptional value and performance. We’re ready to make the process of setting up a multi-CDN smooth and easy for you with expert 24/7 support.
While a multi-CDN setup offers numerous benefits, it comes with associated challenges such as increased architectural complexity and the need for continuous monitoring and optimization. Using the appropriate CDN providers and load balancers is therefore key to unlocking the benefits of a multi-CDN approach.
Speed up your content delivery with Gcore’s next-gen CDN. We boast a comprehensive functionality stack and inbuilt web protection. Our plans are suitable for everyone, from our free-forever plan for personal projects through to highly customized, top-of-the-line options for enterprises.