How Does Multi-CDN Work From a Technical Perspective, and What Technologies are Involved in Making it Possible?

Multi-CDN works by combining several Content Delivery Networks (CDNs) to deliver content more efficiently and reliably. It dynamically routes traffic across multiple CDN providers based on factors like performance, cost, and geographic proximity, ensuring faster load times and better uptime. 

‍

The technologies involved include DNS load balancing, real-time performance monitoring, and intelligent routing algorithms.

‍

Let’s dive deeper into the multi-CDN strategy, and what makes it possible.

‍

What is a Multi-CDN?

‍

A Multi-CDN is exactly what it sounds like: a combination of two or more CDN providers working together to serve content. Instead of relying on a single CDN network, you diversify your content delivery infrastructure, using the best features and advantages of different providers. 

‍

This can help mitigate regional performance issues, avoid outages, and optimize content delivery based on real-time conditions.

‍

The multi-CDN solution offers greater resiliency and speed for global content delivery, which is especially critical for high-traffic websites or applications that need to ensure both performance and availability under different conditions.

‍

Multi-CDN Architecture => How It Works

‍

The multi-CDN architecture is designed to seamlessly switch between multiple CDNs based on pre-defined rules or real-time performance data. This dynamic switching is usually managed through a combination of DNS-based routing, load balancing, and performance monitoring technologies.

‍

Here’s a look at how these components come together:

‍

1. DNS Load Balancing: DNS (Domain Name System) load balancing is at the core of most multi-CDN strategies. When a user requests content, the request is routed to the nearest or most suitable CDN based on factors like location, server availability, and network conditions. A smart DNS resolver decides which CDN will serve the user. DNS queries are resolved to different CDN providers’ edge servers depending on the current state of the network.some text
   • How it works: A DNS resolver sits between the end-user and the CDNs. When a user requests a video, webpage, or any asset, the DNS resolver dynamically selects the best CDN. This can be based on multiple criteria such as geographic location (GeoDNS), latency, or even real-time performance data from monitoring tools.
   • For example, if a CDN in Asia is underperforming, the DNS resolver can route traffic to another CDN provider with better performance in that region.
2. Real-Time Performance Monitoring: Multi-CDN setups rely on real-time monitoring tools to assess the health, performance, and availability of each CDN provider. These tools measure:some text
   • Latency: How long it takes for a CDN to deliver content.
   • Throughput: The amount of data that can be transferred in a given time frame.
   • Availability: If a CDN provider is down or experiencing issues.
3. Solutions like RUM (Real User Monitoring), Synthetic Monitoring, and CDN monitoring services continuously collect data on how each CDN is performing in various regions. This performance data is crucial for making decisions in real-time about which CDN to use.some text
   • Real-world example: If a CDN starts experiencing packet loss or has a higher-than-expected latency in Europe, the monitoring tool detects it, and traffic can be shifted to another CDN provider serving that region more efficiently.
4. Intelligent Traffic Steering: Once the real-time monitoring data is in place, traffic can be routed intelligently based on multiple factors. This is where algorithms come into play. Traffic steering uses rules, policies, and performance data to make the most optimized routing decisions. This can be based on cost, geographic proximity, or the health of the CDN at any given moment.some text
   • Weighted load balancing: In some cases, certain CDN providers may be given more traffic depending on their contract or performance, using weight-based distribution. If one CDN is more cost-effective for a particular region but slower, the traffic might be split in a way that prioritizes performance but also keeps cost in mind.
5. Failover and Redundancy: One of the key benefits of using a multi-CDN strategy is redundancy. If one CDN provider experiences downtime or an outage, traffic can automatically failover to another CDN without disruption to the end-user.some text
   • How it works: By continuously monitoring the health of all CDNs in the pool, the multi-CDN system can quickly detect failures and re-route traffic. This ensures that your content remains accessible even if one CDN goes down.
6. Caching Optimization: Each CDN in a multi-CDN solution maintains its own cache. However, efficient caching is a challenge in multi-CDN environments. That’s because one CDN might cache certain files that another CDN hasn’t yet requested, leading to potential cache misses. Advanced multi-CDN systems address this by pre-fetching or replicating content across CDNs, ensuring content is consistently cached and reducing latency for end-users.some text
   • Edge Cache Coordination: Some multi-CDN platforms try to synchronize content caches between CDNs, so if a user switches between CDNs mid-session, the cached content remains available, improving the continuity of service.

Technologies Involved in Multi-CDN

‍

To make a multi-CDN solution work smoothly, a number of technologies come into play:

‍

1. GeoDNS (Geographic DNS): GeoDNS directs users to the most appropriate CDN edge server based on their geographic location. This helps to reduce latency and ensures that users are served content from a nearby server, making delivery faster.
2. Load Balancers: Load balancers, both DNS-based and application-level, are crucial in a multi-CDN strategy. These tools distribute traffic across CDNs to ensure that no single provider is overwhelmed and that performance is optimized.
3. API Management and Automation: Multi-CDN management often involves using APIs from different CDN providers. Automating CDN management through APIs allows dynamic changes to traffic steering policies, purge caches, and even adjust CDN weight based on performance metrics. This level of automation helps multi-CDN solutions respond faster to network conditions.some text
   • How it works: An automated system continuously evaluates real-time data, making instant changes to which CDN gets the traffic. This eliminates the need for manual intervention.
4. Security Technologies: In a multi-CDN setup, managing security can be more complex due to the need to synchronize DDoS protection, WAF (Web Application Firewall), and SSL certificates across multiple CDNs. This requires consistent security policies across all providers to ensure seamless protection.some text
   • SSL Offloading: Ensuring that each CDN can handle SSL encryption properly is crucial for maintaining secure connections. Many multi-CDN setups involve automated SSL certificate management to prevent conflicts between providers.

‍

Multi-CDN Management

‍

Managing multiple CDNs involves integrating monitoring, traffic steering, load balancing, and analytics into a unified system. 

‍

A multi-CDN management platform allows you to handle multiple providers, configure routing policies, and view performance across all CDNs in real time. 

‍

This can include dashboards that give you insights into:

‍

• Real-time performance metrics for each CDN.
• Traffic distribution across multiple regions and CDNs.
• Cost management to optimize for both performance and budget.

‍