Skip to main content

Content Distribution Network

A content distribution network (CDN in its acronym in English, Content Delivery Network) is a system of distributed servers (network) that deliver web pages and other web content to a user, based on their geographic location. Information technology is based on the principle that the closer the content is to a user's web host, the faster it will be achievable for that person. Response time from the nearby server is shortened and content can be downloaded quickly. CDNs are used primarily for streaming audio and video content, but also for websites with a fundamentally wide coverage to take full advantage of the load distribution of the servers and improve the user experience.

General information

A content distribution network (CDN) is designed to make data available more quickly than conventional hosting. The server-client principle, which is the foundation of any Internet application, is enhanced so that not just one server stores data, but a combination of servers. It originates with a root or node server, which distributes the data to other servers. The data path now depends on the geographic location of the user, because the closer the data is, the faster the recovery.

The root server mirrors the content on a system of servers distributed throughout the world. They react much more quickly to a request, since the path from the server to the user is shorter. Even though telecom data is delivered pretty quickly these days, the equation of speed equals distance versus time also applies here. In the IT industry this refers to loading time. CDN systems also minimize server wait times, incorrect data packets and jitters, while the bandwidth of the Internet connection is used efficiently. Shaking is digital signal interference that occurs, for example, when you make a VOIP phone call and the connection is dropped. CDNs optimize data traffic between the server and the client. They also guarantee a better user experience by reducing waiting and loading times.

File: 600 × 400-CDN-en-01.png

How does it work

A content distribution network does not necessarily have a physical server system. Many times it is implemented by connecting and organizing different servers with each other. This is done through cache and memory systems that are linked through routers. Typically, CDN management software is used to identify the closest server and then distribute the content. Since a copy of the content is stored on all servers in the system, the data is forwarded with the least delay to the user.

First, the place of origin of the query is defined, and then the most appropriate server is determined. That server responds to the HTTP request and sends a response in the form of an HTTP status code; only then does the actual content remain in the form of an HTML document. An average request contains approximately 20 question and answer sequences and takes no more than 3 seconds on average. A CDN is intended to shorten that amount of time and thus improve performance.

There are different types and sizes of CDNs, which are used by small businesses, SMEs, and at the level of large corporations. Content distribution networks are divided into three categories based on size:

  • Edge distribution: Used in small CDNs. Data is transferred from a root server to peripheral devices (peripheral nodes on a network) or directly to the point of presence (POP, the user's Internet access device) for quick retrieval.
  • Border hierarchy: Used for medium-sized CDNs. Hub caches are installed downstream of the root server, which distributes the data of a request to nearby servers.
  • Hub and spoke: Only used for large networks. The data from the root server is mirrored across all connected servers, called hubs. A caching system (the spoke) makes data available to all servers on demand.

Practical relevance

In practice, there are numerous providers of content delivery networks. The selection of an appropriate agent will depend on the requirements. A global company has different needs than an online store. If it is a commercial website, oriented to sales, accessibility and fast loading of content is an important criterion because users leave quickly if the offer does not load in a matter of seconds. Large companies that operate internationally also give importance to good accessibility and performance. In particular, if a site is heavily loaded. CDNs cache such access payloads and promise that, in the case of online stores, the site is always reachable and loads quickly. The same applies to possible DoS attacks, since CDNs regulate the load distribution on the server system. If a hacker attacks, the likelihood of the system crashing is reduced with CDNs.[1]

A selection of CDN solution providers:

  • Akamai
  • CloudFlare
  • Rackspace
  • Amazon CloudFront
  • Edgecast
  • Microsoft Azure
  • KeyCDN
  • Limelight

MirrorBrain, OSSCDN, or CoralCDN also have open source solutions for various systems.

SEO importance

Performance plays a prominent role in the SEO industry. Access, availability and loading time are relevant for search engine optimization. Even though it depends on the purpose of a website, it is generally agreed that these criteria are a factor in Google's positioning. Google recommends constantly checking the loading time, also called page speed, and optimizing it if necessary. There are other programs alongside the webmaster tools that can be used for speed tests. It is recommended to register in the webmaster tools of each search engine, even if CDNs are used.

However, the use of content distribution networks has other consequences that must be observed from the beginning.[2]. IP, domain name and URL may change due to CDN provider. Since IP addresses are always tied to geographic locations, an IP with some broadcast (anycast) is useful, which is then applied to the CDN. Most CDNs use anycast IP addresses for routing[3]. Instead of a domain name with the seller's name, a subdomain is recommended for the CDN system (such as This can be defined by setting the DNS CNAME; then the CNAME refers to a canonical URL with your own domain and not to the provider's name. Some service providers offer this type of configuration at the beginning.

If all the data is hosted on the CDN, it is also useful to separately tag the canonical URLs or choose what data should be loaded from the CDN. For example, many website owners leave images that belong to the content of the website on their own server to avoid losses in ranking. Through the use of the rel = canonical tag and the absolute address, duplicate data content issues can be avoided if all data is hosted on the CDN. At the same time, the CDN should not select its own file name and thus change the directory structure, but the same conventions that previously existed for the domain in question should be maintained. Sometimes redirects have to be set to avoid error codes and non-transmitted data packets.

These technical peculiarities have direct consequences for the optimization of the search engines of the webs. If you don't have a deep understanding of web programming and architecture, either a competent service provider or an agency should be tasked with moving to a CDN in accordance with SEO criteria.


Web Links