Shulou(Shulou.com)06/03 Report--

Content distribution network. The basic idea is to avoid the bottlenecks and links that may affect the speed and stability of data transmission on the Internet, so as to make the content transmission faster and more stable. By placing node servers everywhere in the network to form a layer of intelligent virtual network based on the existing Internet, the CDN system can redirect the user's request to the nearest service node in real time according to the comprehensive information such as network traffic, connection of each node, load status, distance to the user and response time. The purpose is to enable users to access the content they need nearby, solve the congestion problem of Internet network, and improve the response speed of users visiting the site.

What is the principle of cdn acceleration? In fact, the technology of CDN is not complicated, the original core idea is to cache content near the end user. Close to the user, build a cache server, make a copy of the remote content, and put it here.

CDN= 's smarter image + cache + traffic diversion. CDN can not only cache video content, it can also distribute static resources of the website (such as various types of pictures, html, css, js, etc.), and distribute static content of mobile application APP (such as installation package apk files, pictures and videos in APP, etc.).

If a user wants to access the video-on-demand content of a video website, the specific steps of cdn acceleration are:

①, when the user clicks on the content on APP, APP will go to the local DNS (domain name resolution system) to seek IP address resolution according to the URL address.

② and the local DNS system will hand over the resolution right of the domain name to the CDN dedicated DNS server.

Dedicated DNS server for ③ and CDN, which returns the IP address of the global load balancer device of CDN to the user.

④, the user initiates a content URL access request to the load balancer device of CDN.

⑤ and CDN load balancer devices select a cache server in the region to which the user belongs according to the user's IP address and the content URL requested by the user.

The ⑥ and the load balancer device tell the user the IP address of the cache server and let the user initiate a request to the selected cache server.

⑦, the user initiates a request to the cache server, and the cache server responds to the user's request and transmits the content needed by the user to the user terminal.

⑧, if the cache server does not have the content that the user wants, then the cache server will request the content from the source server of the site.

⑨, the source server returns the content to the cache server, and the cache server sends it to the user, and according to the user-defined cache policy, it determines whether to cache the content on the cache server.

In short, CDN uses more cache servers (CDN edge nodes), which are placed in areas or networks where user access is relatively concentrated. When the user visits the website, the global load technology is used to point the user's access to the nearest cache server, and the cache server responds to the user's request.

This is an introduction to the principle of cdn acceleration.

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