A content delivery network (CDN) is a network of servers distributed across data centers around the world that serve to deliver content. By distributing it across multiple data centers, users can view any content without long loading times, regardless of where in the world they are. This would not be possible without a CDN, since the origin server would have to answer and process the individual end-user requests itself. As a result, it would take a lot longer to display images, for example.
Even a failure of the origin server – especially for sites with high traffic – could not be ruled out as a result of the loads. A CDN reduces the latency or the physical distance of requests, which is advantageous for both end users and website operators, as content can be offered in consistent quality worldwide. Incidentally, CDNs are widespread in the field of social media, which is why, for example, posts on social media platforms can be viewed by users all over the world without long loading times.
How does CDN work?
When accessing a CDN, your own web server automatically connects to numerous other servers, which are referred to as replica servers (exact memory images of other servers). The data from your own web server is then transmitted to the replica server via a distribution system. As soon as users access the website and call up certain content, a request-routing system determines the replica server that is best suited to delivering the content. The main thing here is the location of the visitor is crucial.
For example, if the user is located in the United States, the replica server should ideally be located in a state in the United States. The number and distribution of the servers and their transmission capacity varies from provider to provider. Website operators should therefore think carefully about which solution is most suitable for their own purposes. The two crucial components in content delivery are the distribution system and the request-routing system.
a. Delivery of the data using a distribution system
On the one hand, the distribution system helps ensure that the original data is transferred to the replica servers. On the other hand, it ensures that the data is up-to-date and correct. The data is either sent directly to all replica servers or the respective replica servers only receive a message that new data is available if required. However, user requests still have to get to the right servers, for which a request routing system is used. Visitors to a website do not know whether the data comes from the original server or a replica server, since the entire process takes place in the background.
b. Rerouting through request routing system
In order to find a suitable replica server for a request, the request routing system uses specific key figures. In addition to the best connection to the user, which is determined by the average transmission rate and geographic proximity, among other things, the load on the replica server also plays a role. How the different key figures are ultimately weighted depends largely on the requested data. If, for example, streamed media is involved, the priority is a stable connection.
As soon as a suitable replica server has been found, the technical forwarding takes place, with several methods being possible. The simplest is the client-side method, in which the user selects a replica server from a given list. An alternative to this is server-side HTTP 302 redirection, which notifies the user of a suitable replica server that can be contacted automatically. However, the most common method is DNS-based request routing, in which requests are forwarded to a special DNS server within the CDN, which provides the IP address of a replica server.
Why it pays to use a CDN
With a CDN, the latency of a website can be reduced and its speed increased. A CDN is essential, especially when it comes to delivering content to users from all over the world. Especially since website speed has been proven to be a ranking criterion for Google’s algorithm. From an SEO point of view, it makes sense to use a CDN, at least for international sites and sites with sophisticated content.
In this case, sophisticated content means that the website not only consists mainly of text, but also has additional content in the form of images, videos, downloads and comparable content. In order to be able to survive on the market, such content is almost necessary, since readers usually do not want to find a wall of pure text.
However, content such as 4K videos lead to high loading times, which is not only bad for SEO, but also has a negative impact on user satisfaction. Nowadays, the attention span of visitors is extremely short, which is why content should be provided as quickly as possible. Otherwise, a high bounce rate is almost inevitable. Companies in particular should consider using a CDN.
It’s not without reason that there are companies in every industry that are already benefiting from this system of content delivery, and we’re not just talking about retail. Whether in the education sector, the financial sector or the pharmaceutical industry – a CDN is a helpful solution in the age of digitization.
For whom a content delivery network is suitable
Not every website operator needs a CDN and, above all, private individuals who run a website purely for fun can save themselves the additional costs. For companies, on the other hand, things are different. In principle, every company should at least consider using a CDN. Whether a CDN makes sense depends on various factors and some companies can do without it despite the advantages offered. Let’s take a bakery shop as an example.
For a specialty bakery, the customer base will be mostly regional, and while having your own website isn’t a bad thing, it probably won’t generate much traffic. Aside from the fact that most of the sales probably won’t come through the website, a CDN wouldn’t bring much improvement anyway. Neither is high traffic to be expected, nor should the website of a regional bakery shop have many visitors. If, on the other hand, it is a streaming service for films, for example, the whole thing looks different.
1. Corporate CDNs – content and reach are key
Faster loading times are not a bad thing, but as the example above should have made clear, a CDN is not always necessary for companies. At least regional companies should think twice before deciding for or against a CDN. There are two main criteria to consider.
a. Content
First of all there is the content. If a website consists mainly of text, the loading times are usually good anyway. If, on the other hand, images, videos, downloads or even multimedia content are added, this can have a massive impact on the speed. Since not doing so is usually bad for both SEO and user satisfaction, it may be advisable to use a CDN.
b. Reach
The next factor is the reach of the website. For a company in Germany that mainly has customers from Germany, Austria and Switzerland, a centrally located main server is usually sufficient, the performance of which corresponds to the amount of traffic. If, on the other hand, international customers outside the DACH area are added, the use of a CDN is almost mandatory.
Otherwise, a significant proportion of visitors will have to deal with long loading times, which is not exactly good for business. How high the loading times are ultimately depends on the amount of traffic. For this reason, websites with a lot of traffic (especially international) should always think about a CDN, as it is usually the best solution.
2. CDNs don’t just deliver content from websites
Although CDNs are primarily used to deliver website content, they can also be used for other content. Basically, this applies to all types of digitizable data. Especially in times of digital change, every company should be aware of this.
Criteria for choosing a CDN provider
There are many CDN providers out there, which can make it difficult to choose a suitable provider. For this reason, website operators should know the most important criteria when choosing a CDN provider.
1. Geographic reach
Contrary to popular belief, not all CDNs operate globally, which is why geographic reach is always a criterion when choosing a provider. Basically, the provider does not have to be active worldwide, but only in the geographic regions relevant to the company. If the company is really active almost everywhere in the world, a global CDN provider is recommended. It is important that the respective provider meets the GDPR guidelines. This is a crucial factor and one of the most common problems faced by CDN providers from China.
2. Traffic management
In principle, every CDN provider takes on global traffic management for its customers and ensures efficient load distribution. What is not guaranteed, however, is the so-called Origin Shield, which shields the origin server from additional traffic. In order to avoid overloading, it is better to rely on a provider with Origin Shield, especially for websites with high traffic.
3. Network security
In the age of digitization, cyber attacks are among the greatest risks for companies, as they can cause massive financial damage. Network security is therefore also an important criterion when choosing a CDN provider. In addition to defending against distributed denial of service (DDoS) attacks, unauthorized access should be filtered out. It is also good if there is an integrated web application firewall (WAF) and SSL encryption. However, the security of the network should not come at the expense of performance. This is also important to consider when choosing a provider.
4. Range of functions
CDNs can have a variety of features, so website operators should always research the feature set ahead of time. Some important features would be image management, advanced caching, dynamic acceleration, and front-end optimization.
5. Quality of support
A good customer service should be available 24/7 and able to help with problems or queries. In addition, the provider should have a managed service team with qualified specialists. In principle, in such cases it is even advisable for website operators to involve the CDN provider in the development of their own website(s).
6. Costs
The costs incurred should be fixed in advance and fit the website operator’s budget. In addition to the provision and storage of data, there may be costs for support and additional services.
Pros and cons of CDN
Using a content delivery network has both advantages and disadvantages.
Advantages of CDN
Here are the benefits of content delivery networks.
a. Faster loading times
By caching data on the replica servers, CDNs enable faster loading times, which is important for both user satisfaction and SEO.
b. Lower bandwidth usage
CDNs contribute to lower bandwidth usage through their replica servers. This ensures that content remains available even with high user numbers or server failures.
c. Better performance
Lower bandwidth utilization and faster loading times automatically contribute to better website performance. Also, many CDNs offer self-service tools to further optimize performance.
d. Greater security
Since requests are forwarded through a CDN, this can contribute to a higher security of the cached data. If companies keep sensitive data away from the respective CDN and thus minimize the attack surface, DDoS attacks and web-based exploits such as SQLis, for example, do not even reach the original server.
e. Scope for analysis
A significant amount of traffic on the internet is carried by CDN providers and as a result they have a lot of data at their disposal. This data includes, for example, important information about users that can be used for analysis. This allows, among other things, the end user interaction with certain content to be measured.
f. Flexible scalability
A CDN can adapt to new bandwidth requirements in real time without having to pay for more bandwidth than needed. Since the bandwidth requirements of companies can change in a very short time, this offers greater flexibility.
g. Lower hosting costs
With a CDN, websites require fewer web hosting resources because the management of static content is taken over. This reduces the cost of hosting.
h. Numerous possible uses
The possible uses of a CDN are diverse, which is why the digital solutions are ideal for companies in a wide variety of industries.
Disadvantages of CDN
Here are the cons of content delivery networks.
a. Higher effort
Both the setup and the operation of a CDN involve more effort because the data is no longer on a single server.
b. More gateways for hackers
CDN security is a critical issue. In principle, the replica servers protect the original server from attacks, but on the other hand there are more entry points for hackers, which is why companies have to be careful with sensitive data.
c. Loss of control
Since your own data is no longer only on your own server, but also on several replica servers, a CDN is associated with a certain loss of control.
d. Suboptimal for dynamic content
Dynamic content such as news tickers and shopping carts access their own databases and are not suitable for caching, which is why CDNs (in contrast to static content) perform less than optimally.
e. SEO problems
Faster loading times are good for SEO, but a CND can still be problematic from an SEO perspective because content is hosted on external servers. The content on the CDN may therefore not be current. For example, there is an increased risk with image descriptions and snippets.
Conclusion
While CDNs, like other digital solutions, are not without drawbacks, they do come with some key benefits. Whether it ultimately makes sense to use it depends on the company in question. Visitors primarily benefit from faster loading times, which contributes to greater satisfaction and thus also benefits website operators. In general, the performance of a website can be improved immensely by using a CDN.
