How to correctly set up a Multi-CDN

A CDN speeds up content delivery.

A decent network with a large number of points of presence helps increase the speed of a website or app and reduces delays in video broadcasts. But sometimes one CDN may not be enough to solve every problem your business faces, and you have to use several.

What is a Multi-CDN?

A Multi-CDN is a combination of different CDNs. This solution helps to achieve better performance and fault tolerance. But more resources also cost more. Therefore, a Multi-CDN is not suitable in every case.

Let’s figure out in which cases the use of several content delivery networks will be optimal, and how to properly distribute the load among them.

What tasks does a Multi-CDN solve?

1. Increased fault tolerance

If you use a CDN from one provider, you depend entirely on the reliability of their network. If there is a major failure, your resources will be unavailable.

If you use multiple CDNs, you can redistribute the load to other networks in the event of a disaster, so that your users won’t notice anything at all.

If it’s critical for you that your resources remain available at all times, a Multi-CDN is the right solution.

2. Good coverage

For a CDN to work at maximum efficiency, its points of presence need to be located as close to the end users as possible. It’s best to find a provider whose cache servers are located in the same regions that you serve. Then, one network will do the job perfectly.

But this is not always the case. Let’s say some of your clients live in Canada. There is a provider that provides excellent coverage in that country. But they have very few points of presence in the US, where many of your users also live.

In this case, the best solution would be to find another company with good coverage in the US and connect both networks. Canadian traffic will go through one CDN, and US traffic through another.

3. Better performance

If you use several CDNs, you have more points of presence, more routes, and better bandwidth, which means that the content delivery speed is much higher. This is especially useful when there are large bursts of traffic and one network cannot handle the load.

Different CDNs also have different features. Some providers are better at delivering “heavy” images and videos, while others are ideal for dynamic content.

If you haven’t found a provider that meets all your requirements 100%, a use Multi-CDN. This way, you can deliver different types of content across different networks, thereby combining their benefits and speeding up your resources.

4. Reduced cost

Providers may have different prices for content delivery in different regions. Imagine you’re choosing between two companies that suit you equally well. But one offers a good CDN price in America and a very high price in Europe, while the other offers the opposite.

In order not to have to choose the lesser of two evils, connect both CDNs, but redirect traffic so that in each region it goes over a cheaper network. This saves you money.

Smartly distribute the load among different CDNs

Determine the basic idea behind traffic balancing

How you distribute the load depends on what you are using the Multi-CDN for.

1. You can redirect traffic on a geographical basis: requests from different regions go over their respective networks. This method is suitable if several CDNs provide you with good coverage or help reduce the cost of delivering content to different locations.
2. You can divide content into groups and deliver it through different CDNs. This will improve performance and fault tolerance. Each network will be responsible for the content it delivers best.
3. You can balance the load by volume: specify what percent of the traffic goes through each network. It will also help improve fault tolerance.

Look at the statistics

To see if you have distributed the load correctly, check how the network is performing.

Take a look at the statistics. Be sure to ask the providers for raw logs, which can be used to analyze the CDN’s performance.

To analyze the performance correctly, it’s desirable that the monitoring parameters be as consistent as possible with each other: providers compose reports for the same periods of time, the data sets about the CDN operation are equally complete, and the statistical parameters are the same.

You may not be able to fully align the monitoring strategies for each network. Each provider has its own statistics and its own logic by which it’s provided. For example, one company may provide a report on the amount of traffic from different countries, while another doesn’t offer that option.

However, agreeing on some parameters and bringing reports from different providers into accordance is in your power.

1. Request statistics for each CDN at the same time and for the same period.
2. Specify the same HTTP headers that CDN servers will add to requests and responses to make it easier to parse the data later.
3. If your provider offers extended statistics for an additional fee, use this service to get as much information as possible, and to have more opportunities for analyzing network performance.

Enable origin shielding

A huge number of requests come from several CDNs to one server. There can be so many of them that the origin simply can’t cope.

Shielding will help you avoid this situation. It provides additional protection against overloading the origin.

All requests from a CDN first go to a special pre-cache server, and from there to the origin. Thus, only one server communicates with the origin, not the entire network. The number of connections is reduced this way, which means less load and higher productivity.

Traffic balancing with a DNS

You can distribute the load between different CDNs using our DNS hosting. It allows our customers to redirect requests based on user location or on a set percentage.

How to distribute traffic by region?

1. Create a DNS zone with a domain to balance it.
2. Create a CNAME record for the region. In the Name field, enter the subdomain and the region name in the following format: subdomain.region.
3. In the Record Content field, specify the zone or domain where requests from the region will be sent. A zone name or domain name must end with a period.
4. Click Create.

Repeat these steps for each region, requests from which should be directed to different CDNs.

However, you don’t have to create CNAME records for each region separately. For example, if you’re using two CDNs, and you want traffic from Australia to go over one network and the rest over another, you only need to create two CNAME records: one for traffic from Australia, and one for the rest of it.

To create a record for all other regions, in the Name field, specify the balanced subdomain without a region, and in the Record Content field specify the zone where requests will be sent.

How to distribute traffic by percentage?

1. Create a DNS zone with a domain to balance it.
2. Create a CNAME record. In the Name field, specify the subdomain. In the Record Content field, specify the zone where the traffic will be directed (its name must end with a period).
3. In the Proportion field, specify what percentage of requests will go through this CDN.
4. Click Create.

Repeat these steps for each CDN.

Read more about configuring DNS balancing in our Knowledge Base.

Connect our DNS hosting for free to easily manage your Multi-CDN.

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Try out a powerful CDN

Looking to leverage your Multi-CDN strategy with a powerful, fast, and secure network?

Test the Gcore CDN, a truly global network with advanced content delivery and security features.

Gcore CDN figures as of early 2021:

• More than 75 points of presence on 5 continents
• More than 650 cache servers around the world
• 50+ Tbps of total network capacity
• Average global response time of under 30 ms

To get started, try routing 20% of your traffic through our network. Analyze the performance and costs at the selected time frame and at peak loads.

Or, start with a free consultation.

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