What is content delivery network (CDN)?

1 points

A Content Delivery Network is a network of servers in different data centers around the world.These represent an excellent opportunity to develop a web page or application worldwide. When you access these types of networks, your web server is automatically connected to a large number of servers. With the help of a management system, the static content of your web server is transferred to so-called replica servers. If users request only certain content from your web page, the Request Routing System determines which replica server is the most appropriate in the content distribution network for the delivery of the requested data. The number and distribution of the server, as well as the degree of integration of powerful backbone networks, will depend on the CDN Wiki provider.

How does data transfer work on CDN?

When a user browses the Internet, they do not receive any information as to whether the data is being retrieved from the source server of a particular web page or if they are doing so from a replica server. The data transfer process is usually executed in the background and is evidenced by shorter load times.

The two most important components involved in the operation are the distribution system and the Request Routing System. The distribution system not only transmits the contents of the source server to the replica server but also guarantees authenticity and quality. There are two possible approaches: in the first, the distribution system sends new and modified files immediately to all Content Delivery Networks servers, while in the second, a message is sent to the replica servers informing them that the current data is available and, if necessary, will be requested. This is where the Request Routing System is responsible for ensuring that user requests reach the appropriate server. Thus, with these simple steps, this ensures that applications are managed optimally.

Finding the Right Replica Server

The first step is to find the most suitable server to respond to the user’s request. To achieve this, the Request Routing System focuses on specific indicators determined by different measurement methods.  

The weighting of the different indicators will always depend on the data requested. For example, those dynamically generated content will get better indicators from the server side, while a stable connection between the client and the server will be essential for the use of Streaming Media.

Redirection of an application

Once the target server is defined in CDN, the next step will be the technical redirection of the request through the Request Routing System. There are several methods for this “Request Redirection” and its application differs mainly depending on where it is done (from the client, the network or the replica server).

Redirecting the request by the client is a simple implementation method, in which the client will select the replication server from a list. Its main disadvantage is, however, that the Content Delivery Network has little influence on the allocation process. The redirection from the server – HTTP 302 Redirection – is very easy to implement and is very well equipped with information about the CDN. In this case, the outgoing server responds to the request with the HTTP status code and communicates it to the client via the given replica server, which is automatically contacted through another request. The main disadvantage of this method is the duplication of the required connections.

The most commonly used type of redirection is DNS Request Routing. In this, the request made by the client to the local DNS server is redirected within a Content Delivery Network, which in turn sends the IP address of the replica server back. The biggest disadvantage of this method is that the accesses are delayed as a result of the constant repetition in the references to the Domain Name System.

Why is it worth using CDN?

Thanks to globally localized servers, users of a Content Delivery Network benefit primarily from fast load times and reduced bandwidth usage. As a web operator, the advantages of using CDN include a reduction in the use of the web server and an increase in the security of the cached data – requiring, for example, DDoS attacks – as a result of the redirects of the requests, since with these it is not possible to reach the source server. At this point, the requirement is only that confidential information, such as user data or passwords, be kept outside the CDN since its storage implies an increased risk of attack and often generates conflicts of privacy. Another useful feature is the assignment of a unique domain for Content Delivery Network content. In this way, in the case of an attack by malicious people, it avoids its propagation to other elements of the web page. The following list summarizes the benefits of a CDN:

Static elements such as HTML pages, images, style sheets, documents, or client-side scripts are cached on the replica server and do not have to be retrieved from the web server. This protects servers and ensures shorter load times for users, which is reflected in the decline in rebound rate and good positioning in search engines.

The low utilization of the server and the applications involved avoid overloads and reduces the risk of possible damages or failures. This has a positive effect on the hardware requirements for web hosting.

Websites that offer streaming music and video services benefit from the use of a CDN as it handles large amounts of data in short periods of time. This also applies to live webcasts.

The load times are not only reduced but also reduce the consumption of bandwidth, which is directly related to loading requests of the contents of your website.

The security of your server and, therefore, of your data and applications used increases thanks to the use of a Content Delivery Network because it is possible to identify possible attacks to be avoided in time.


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