Multi-CDN: what if one content delivery network is not enough?

clock • 6 min read

Using more than one provider can lower costs and improve resilience

Even if you use a high-quality provider for your content delivery network (CDN), a single network may not be enough for your business. In such cases, it is necessary to use multi-CDN; that is, several content delivery networks united in one. This solution helps achieve better performance and fault tolerance, but is more expensive. In this article we'll be looking at the situations where the use of several CDNs is optimal, and how to properly balance the load among them.

Why use multi-CDN?

1. Increased fault tolerance

If your business fully depends on a CDN, relying on just one provider is risky. Even the leading providers sometimes face major failures that make their users' content unavailable. Using multiple CDNs allows customers to redistribute the load to other networks in the event of a disaster, so their users don't notice a fault.

If it is critical that your business's 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 with more than 100 points of presence across 5 continents (such as G-Core Labs). But, this is not always the case. Let's imagine that you cooperate with a provider featuring excellent coverage in Canada. But if you launch your product on a new market, e.g. in Eastern Europe, you are likely to find out that your provider has very few points of presence there. In this case, the best solution would be to find another company with good coverage in the new region and to connect both networks. Your Canadian traffic will go through one CDN, and your Eastern European traffic through the other.

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 cope with the load. In such cases, it is useful to have a powerful content delivery network as part of your multi-CDN. For example, with G-Core Labs it is possible to quickly deliver heavy content to outlying regions even in times of critical load. The total capacity of the provider's network is 50 Tbit/s, and its monthly peak loads reach 3.5 Tbit/s. To ensure a trouble-free operation during such times, the CDN uses solutions powered by second & third-gen Intel Xeon scalable processors, and the network itself has 6,000 peering partners.

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 per cent, use a multi-CDN. This way, you will be able to 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 of them offers a good CDN price in America and a very high price in Europe, while the other one offers the opposite. To avoid a situation of choosing the lesser of two evils, connect both CDNs but redirect traffic to go over a cheaper network in each region. This saves you money.

Smartly distribute the load among different CDNs

Determine the basic idea behind traffic balancing

How you balance the load depends on the way in which you are using the multi-CDN:

  • Redirecting traffic geographically. You can distribute your traffic properly and let requests from different regions go over their respective networks. This method is suitable if several CDNs provide you with good coverage on different continents, or if you want to reduce the cost of delivering content to different locations.
  • Dividing content into groups based on its type. You can divide content into groups based on its type and deliver it through different CDNs. This will improve performance and fault tolerance. Each CDN will be responsible for the content it delivers best.
  • Balancing the load by content volume. To enhance fault tolerance, you can specify what percent of traffic goes through each network.

Look at the statistics

To make sure that you have balanced the load correctly, regularly check how the delivery network is performing. Be sure to ask the providers for raw logs that you can use to analyse the CDN's performance. It's desirable that the monitoring parameters be as consistent with each other as possible. To achieve this, make sure that the providers compose reports for the same periods of time; the CDN operation data sets 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 logic by which it's provided. However, agreeing on some parameters and bringing reports from different providers into accordance is in your power. Here's how you can do it:

  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, take advantage of this service to get as much information as possible and to have more opportunities for analysing network performance.

Enable origin shielding

A huge number of requests come from several CDNs to one server. There can be so many that the origin simply can't cope. Shielding will help prevent this situation, providing 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. In this way the number of connections is reduced, meaning less load and higher productivity.

Try G-Core Labs CDN for free

G-Core Labs users can leverage their multi-CDN strategy with a powerful, fast, and secure network. It includes more than 100 points of presence in 100+ cities all over the world and was awarded a Guinness World Record. The CDN supports all the necessary protocols including HTTP/2, SSL and IPv6 and allows you to use flexible system settings like API access, heavy content preloading, and full or selective cache flush.

During the first 14 days, you can test G-Core Labs CDN for free. This will allow you to check the network performance at peak loads. To get started, try routing 20% or any other amount of your traffic through our network and then analyse the performance and costs at the selected time frame.

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