What is the CDN

The full name of CDN is Content Delivery Network, which is also called Content Delivery Network. CDN is an intelligent virtual network built on the basis of the existing network. It relies on the edge servers deployed in various places, through the central platform of load balancing, content distribution, scheduling and other functional modules, users can get the content nearby, reduce network congestion, and improve user access response speed and hit ratio.

CDN is the use of caching technology, to solve the problem of how to quickly and reliably transfer data from the source to the user. When users obtain data, they do not need to obtain data directly from the source site. Through CDN distribution, users can obtain data from a better server, so as to achieve fast access and reduce the load pressure of the source site.

CDN fast access reason

Q: why don’t we get the data directly from the source site instead of forwarding it through the CDN?

If the data on the network is returned directly from the source site to the user, there is a high probability of network congestion and server overload. So if you can have a technology that can cache data in the nearest place to the user, so that the user can get it at the fastest speed, then you can reduce the pressure, reduce the congestion of network transmission, play a big role. CDN is such a technical scheme, thus conceived.

Principle of CDN

CDN basic principle is to use various cache server * *, * * the cache server distribution to the user access relatively concentrated area or in the network, when users visit the web site, using the global load technology will work user access point to the nearest normal cache server, directly by the cache server response to user requests.

The general process for users to access websites without CDN acceleration through browsers is as follows:

  1. The user enters the domain name to visit in the browser.
  2. The browser requests the DNS server to resolve the domain name.
  3. The DNS server returns the IP address of the domain name to the browser.
  4. The browser uses this IP address to send requests to the server.
  5. The server returns the requested content to the browser;

The user visits a website that uses a CDN, and the process will look like this:

  1. The user enters the browserwww.processon.comFor this domain name, the first time the browser finds that there is no DNS cache, it requests the DNS server of the website.
  2. The browser requests the DNS server to resolve the domain name. As the CDN adjusts the domain name, the DNS server will eventually hand over the resolution of the domain nameCNAMEPoint to the DNS server dedicated to the CDN;
  3. CND’s DNS load balancing system resolves domain names and returns the IP addresses that respond fastest to users.
  4. The user makes a request to the IP address (CND server);
  5. CND load balancing equipment will choose a suitable cache server for users to provide services;
  6. The user makes a request to the cache server;
  7. The cache server responds to the user request and returns the content required by the user to the user.

conclusion

After the introduction of CDN between the website and users, users will not have any different feelings from the original. The basic idea of CDN is to avoid the bottlenecks and links on the Internet that may affect the speed and stability of data transmission as much as possible, so as to make the content transmission faster and more stable. CDN is to allow users to access the website with the shortest path and the fastest speed to reduce the load pressure of the source station center.