Key Takeaways
- A multi-CDN setup delivers content through two or more CDN providers, with a routing layer that picks a provider for each request based on location, performance, availability, or cost.
- The main benefits are higher availability during provider outages, better performance across regions, and more pricing flexibility. The tradeoff is extra configuration, monitoring, and security work across providers.
- Common implementation methods include DNS load balancing, primary-fallback, performance-based routing, and turnkey platforms. Managed services can take over routing and failover entirely.
A content delivery network (CDN) caches your content on servers close to users, so pages, images, and video load faster and your origin server handles fewer requests. Most sites start with a single CDN provider. That works well until the provider has an outage, performs poorly in a region you care about, or gets expensive at your traffic volume.
Multi-CDN addresses those limits by spreading delivery across two or more providers. This guide covers how multi-CDN routing works, the benefits and tradeoffs, the main implementation methods, and best practices for running a multi-CDN strategy.
In this article:
- What Is a Multi-CDN?
- How Multi-CDNs Work
- CDN vs. Multi-CDN: What Is the Difference?
- 8 Benefits of Multi-CDN
- Things to Consider When Implementing Multi-CDN
- Multi-CDN Implementation Methods
- Using a Managed Multi-CDN Solution for Images and Video
- Best Practices for Your Multi-CDN Strategy
What Is a Multi-CDN?
A multi-CDN setup uses two or more CDN providers to deliver the same website, app, or media library. A routing layer decides which provider serves each request based on factors like the user’s location, each CDN’s current performance and availability, or cost.
Teams usually adopt multi-CDN to keep content available when one provider has an outage, to serve each region from whichever CDN performs best there, and to avoid depending on a single vendor’s pricing and capacity. The tradeoff is added complexity, since each provider has its own configuration, security settings, and logs to keep aligned.
How Multi-CDNs Work
Multi-CDN systems distribute traffic across several CDNs, and the routing method decides which one serves each request. Here are the most common approaches:
- Static DNS: Fixed DNS entries send specific traffic to specific CDNs. For instance, traffic for highspeedvideo.domain might go to one CDN, while static.downloads.domain goes to another. It’s simple to set up, but there’s no automatic failover, and routing doesn’t account for cost or performance.
- Managed DNS: A managed DNS service adds smart routing on top of static entries, which reduces manual intervention and improves fault tolerance. Like static DNS, it doesn’t factor cost or performance into routing decisions.
- Round-robin: Requests go to each CDN in turn. With two CDNs, the first request goes to CDN-A, the second to CDN-B, the third back to CDN-A, and so on. Weighted round-robin skews the split, such as 50% to CDN-A, 30% to CDN-B, and 20% to CDN-C.
- Geolocation: Each request goes to the CDN closest to the user, which reduces latency.
- Variable-driven load balancing: Routing decisions combine several factors, such as cost, performance, location, and weights, in real time. It’s the most complex method to configure but gives the most control over cost and performance.
Key Components of a Multi-CDN Solution
- Provider Selection: Organizations choose multiple CDN providers based on geographic coverage, performance, pricing, and specialized features.
- Traffic Management: Traffic management tools (like global traffic managers or DNS-based routing) direct user requests to the optimal CDN based on real-time factors like location, performance, and cost.
- Continuous Monitoring: Ongoing monitoring of each CDN’s performance enables dynamic adjustments, ensuring optimal delivery and cost-efficiency.
CDN vs. Multi-CDN: What Is the Difference?
Multi CDN involves using multiple CDN providers to distribute content to end-users. Instead of relying on a single CDN provider, Multi CDN combines the resources of multiple CDNs to improve the reliability, performance, and resilience of content delivery.
The practical differences show up in how each setup handles failures, regional performance, and day-to-day operations:
| Factor | Single CDN | Multi-CDN |
|---|---|---|
| Outage Impact | An outage or regional slowdown affects all traffic until the provider resolves it | Traffic shifts to another provider, manually or automatically depending on the routing method |
| Regional Performance | Limited to one provider’s network and peering in each region | Each region can be served by whichever provider performs best there |
| Pricing | One contract and rate card | Traffic can favor lower-cost providers by region, and a second vendor strengthens your position in contract negotiations |
| Configuration | One set of caching, security, and purge rules | Rules must be kept consistent across providers |
| Monitoring | One dashboard and log format | Logs and metrics from several providers need to be combined |
| Best Fit | Sites with a regional audience or moderate traffic | High-traffic sites with global audiences, strict uptime requirements, or large media libraries |
For many sites, a single well-configured CDN is enough. Multi-CDN starts to pay off when the cost of an outage or slow regional performance outweighs the extra operational work.
8 Benefits of Multi-CDN
Here are the main benefits of implementing multi CDN:
1. Improved Reliability
Multi CDN helps to ensure that content is delivered even if one of the CDN providers experiences an outage or slowdown. By using multiple CDN providers, content delivery is balanced across different networks, reducing the risk of congestion or failure in a single network.
2. Better Performance
By selecting the best CDN provider for a particular location or user, Multi CDN enables organizations to optimize content delivery and improve performance. This can lead to lower latency, faster page load times, and a better overall user experience.
3. Increased Resilience
Multi CDN provides a fallback solution in the event of an outage or slowdown with one CDN provider, ensuring that content delivery continues without disruption. This helps to ensure that users can always access the content they need, even in the face of technical issues.
4. Global Coverage
Multi CDN allows organizations to use the best CDN provider for each location, ensuring that content is delivered efficiently and effectively to users around the world. This is particularly important for organizations with a global customer base, as it helps to ensure that users have a consistent and high-quality experience, no matter where they are located.
5. Better DDoS Resilience
Spreading traffic across several providers gives you more combined network capacity to absorb a volumetric DDoS attack, and a way to move traffic elsewhere if one provider is overwhelmed. This doesn’t make a breach less likely on its own. Each added provider is another set of WAF rules, bot protection, and access controls to keep consistent, so security policies need to be aligned across every CDN in the setup.
6. Cost Savings
By selecting the best CDN provider for each location, organizations can reduce costs and optimize their content delivery spend. This can be achieved by selecting a CDN provider that offers the best combination of performance, reliability, and cost-effectiveness for a particular location.
7. Enhanced Flexibility
Multi CDN provides organizations with the ability to switch between CDN providers on the fly, ensuring that they can always use the best solution for their needs. This enables organizations to respond quickly to changes in their content delivery requirements, and to take advantage of new opportunities as they arise.
For example, you might route video through a provider with strong streaming performance and use another for its security features or cache controls.
8. Improved Scalability
Multi CDN enables organizations to scale their content delivery quickly and easily, providing the resources necessary to support rapid growth. This is particularly important for organizations that are experiencing rapid expansion, as it helps to ensure that their content delivery infrastructure can keep up with their growth.
Things to Consider When Implementing Multi-CDN
- Complexity: Multi-CDN setups are more complex than single-CDN solutions, requiring careful planning, integration, and ongoing management.
- Integration: Getting several CDN providers to work consistently with each other and your existing infrastructure can be challenging.
- Initial and Ongoing Costs: While multi-CDN can lead to long-term savings, the initial setup and management may incur higher costs compared to a single provider.
Pro Tip!
Get multi-CDN delivery without managing the CDNs yourself.
Cloudinary’s Enterprise plans route each image and video request through CDN partners such as Akamai, Fastly, and Cloudflare, using real-time data on location, load, and availability. Your asset URLs stay the same even if the CDN setup changes.
Multi-CDN Implementation Methods
DNS Load Balancing
This is a method of distributing content delivery across multiple CDN providers using DNS (Domain Name System) to direct traffic to the best CDN for a particular location. In this method, the DNS server acts as a load balancer, directing traffic to the best CDN provider for a particular location, based on factors such as network performance, availability, and cost.
Advantages of DNS load balancing:
- Simple to implement: DNS Load Balancing is relatively easy to implement and does not require a complex network infrastructure.
- Flexible: The load balancing decision can be easily changed based on real-time performance data.
- Scalable: DNS load balancing can be easily scaled to accommodate changing content delivery requirements.
Disadvantages of DNS load balancing:
- Limited control: DNS load balancing provides limited control over the content delivery process, as it is dependent on the performance of the underlying network infrastructure.
- Limited performance: The performance of DNS load balancing may be limited by the speed and efficiency of the DNS servers.
- Vulnerability: DNS load balancing can be vulnerable to security threats, such as Distributed Denial of Service (DDoS) attacks, which can disrupt the content delivery process.
Primary-Fallback Scheme
This is a method of distributing content delivery across multiple CDN providers, where one CDN provider is designated as the primary provider, and others are used as fallback providers. In the event of an outage or slowdown with the primary provider, traffic is redirected to one of the fallback providers, ensuring that content delivery continues without disruption.
Advantages of the primary-fallback scheme:
- Reliable: The primary-fallback scheme provides a reliable content delivery solution, as it ensures that content is always available, even in the event of an outage or slowdown with the primary provider.
- Simple to implement: The primary-fallback scheme is relatively simple to implement, and does not require a complex network infrastructure.
Disadvantages of the primary-fallback scheme:
- Limited control: The primary-fallback scheme provides limited control over the content delivery process, as it is dependent on the performance of the underlying network infrastructure.
- Inflexible: The primary-fallback configuration may not be ideal for all locations or user groups, leading to suboptimal content delivery performance.
Performance Data-Driven Load Balancing
This is a method of distributing content delivery across multiple CDN providers, based on real-time performance data. In this method, performance metrics such as network latency, throughput, and availability are used to determine the best CDN provider for a particular location, ensuring that content is delivered to users quickly and efficiently.
Advantages of performance data-driven load balancing:
- Optimal performance: This method provides the best possible content delivery performance, as it is based on real-time data about the underlying network infrastructure.
- Flexible: The load balancing decision can be easily changed based on changing performance data, ensuring that content delivery is always optimized.
Disadvantages of performance data-driven load balancing:
- Complex to implement: This method requires a complex network infrastructure and specialized knowledge to implement effectively.
- Increased costs: Performance data-driven load balancing may result in increased costs, as it requires the use of specialized hardware or software.
Turnkey Multi-CDN Platform
Turnkey multi CDN is a turnkey solution for distributing content delivery across multiple CDN providers, which is provided by third-party service providers. With turnkey multi CDN, the service provider manages all aspects of the multi CDN implementation, including the selection and integration of CDN providers, load balancing, and performance monitoring.
Advantages of turnkey multi CDN:
- Simplified implementation: This method simplifies the implementation of multi CDN, as the service provider takes care of all the technical aspects of the implementation.
- Improved performance: Turnkey multi CDN provides improved content delivery performance, as the service provider has expertise in selecting and integrating multiple CDN providers.
- Reduced costs: This method can result in reduced costs, as the service provider may be able to negotiate better pricing from CDN providers due to their volume of business.
Disadvantages of turnkey multi CDN:
- Limited control: The service provider has control over the content delivery process, and the user may have limited control over the configuration of the solution.
- Dependent on the service provider: Turnkey multi CDN is dependent on the performance and reliability of the service provider, which may result in a loss of control and visibility into the content delivery process.
Using a Managed Multi-CDN Solution for Images and Video
A turnkey platform takes over the routing work, but the files it delivers still need to be the right format and size for each device. For media-heavy sites, a managed service can handle both steps: preparing each image or video for the requesting device, then choosing which CDN delivers it.
With Cloudinary’s multi-CDN delivery, each asset’s format, quality, and dimensions are adjusted before delivery, and the request is then routed through CDN partners such as Akamai, Fastly, and Cloudflare. Routing decisions use real-time data on:
- The user’s location
- Current load on each CDN
- Each CDN’s availability
If a CDN has an outage or its performance degrades, requests move to another partner automatically. Cloudinary also handles the CDN configuration and domain mapping, so your asset URLs don’t change when the CDN setup does. This moves the traffic steering and failover logic described in the implementation methods above out of your own infrastructure.
Dynamic multi-CDN switching is an Enterprise plan feature, and enabling it affects pricing. The available setups are covered in the CDN delivery options documentation.
Best Practices for Your Multi-CDN Strategy
Group Content by Type
By grouping content by type, organizations can ensure that the most appropriate CDN provider is delivering each type of content. For example, static content, such as images and HTML pages, may be best delivered by one CDN provider, while video content may be best delivered by another. This helps to ensure that each CDN provider is delivering the type of content that they are best suited to handle, improving overall performance.
Institute Consistent Hashing of Your Working Set
Consistent hashing is a way of distributing content across multiple CDN providers in a balanced manner. It involves dividing the content into segments and then mapping each segment to a specific CDN provider, based on their strengths and weaknesses. This helps to ensure that the load is distributed evenly across the CDN providers, improving overall performance and reliability.
Establish Consistent Monitoring Parameters
To effectively manage a multi CDN implementation, you need a consistent approach to monitoring performance. This includes monitoring the performance of each CDN provider, as well as the overall performance of the multi CDN solution. This helps to quickly identify and address any issues that arise, and to ensure that the multi CDN solution is functioning optimally.
Seek Feature Parity Across Providers
When selecting multiple CDN providers, look beyond each provider’s technical capabilities and aim for feature parity between providers, to ensure that the multi CDN solution provides a consistent level of functionality and performance.
Choosing the Right Multi-CDN Approach
A single CDN is often enough for sites with a regional audience. Once outages, uneven regional performance, or delivery costs start affecting your users or budget, adding a second provider is worth evaluating.
Start with the method that matches your team’s capacity. DNS load balancing and primary-fallback setups are the simplest ways to add redundancy. Performance data-driven routing gives better results but needs ongoing monitoring and tuning. Whichever you choose, keep caching rules, security policies, and monitoring consistent across providers so users get the same experience no matter which CDN serves them.
If your team would rather not run the routing layer itself, Cloudinary’s Enterprise plans deliver images and video through multiple CDN partners with real-time, automatic switching. Contact our sales team to see how multi-CDN delivery would work for your media library.
Frequently Asked Questions
What Does CDN Stand For?
CDN stands for content delivery network. It’s a distributed network of servers that caches content close to users to reduce load times. A multi-CDN setup uses more than one of these networks at the same time.
What’s the Difference Between a CDN and a Load Balancer?
A load balancer distributes requests across servers within one environment, such as several origin servers. A CDN caches and serves content from servers spread around the world. In a multi-CDN setup, a load balancing layer (often DNS-based) decides which CDN handles each request.
What Is a Multi-CDN Strategy?
A multi-CDN strategy is a plan for how traffic is split across CDN providers and when it moves between them. It typically defines the routing method, the failover rules, and the metrics used to compare providers.
What’s the Benefit of Delivering Content Through Multiple CDN Providers?
The main benefit is availability. If one provider or network path has problems, traffic moves to another, so content stays reachable. It can also improve performance in regions where one provider outperforms another.
