A CDN consists of an initial server, a cache server distributed at the edge, a redirect DNS server and a content exchange server. The initial server is responsible for generating server information content; The cache server is responsible for storing part or all of the information content of the initial server;
Redirect DNS server to provide users with the nearest server IP address to reduce the pressure on backbone network; The content exchange server completes the load balancing function between cache servers; The content management server is responsible for managing the content stored by all cache servers in the whole network, and making corresponding cache strategies for each cache server to improve the service quality of the cache servers.
Working principle of extended data CDN network
1. When the user clicks on the content URL on the website page, after the local DNS system resolves, the DNS system will finally hand over the domain name resolution right to the CDN dedicated DNS server pointed by CNAME.
2. The DNS server of CDN returns the global load balancing device IP address of CDN to the user.
3. The user initiates a content URL access request to the global load balancing device of the CDN.
4.CDN global load balancing equipment selects a regional load balancing equipment in the user's area according to the user's IP address and the content URL requested by the user, and tells the user to send a request to this equipment.
5. The regional load balancing equipment will select an appropriate cache server to provide services for users. The basis of selection includes: judging which server is closest to the user according to the IP address of the user.
6. The global load balancing device returns the IP address of the server to the user.
7. The user initiates a request to the cache server, and the cache server responds to the user's request and sends the content needed by the user to the user terminal. If there is no content that users want on this cache server, and the regional balancing device still distributes it to users, then this server will request the content from its superior cache server until the source server traced back to the website pulls the content locally.