What is the "CDN" where a large -scale online disorder occurred?I actually accessed it and checked it

Distributed reverse proxy server

　The CDN is an acronym for "Content Delivery Network" and plays a role in smoothing the flow of data exchanged on the Internet.As an example, the familiarity is to use it on a website.

　The data on the website we see usually is stored on the web server on the Internet, and you can display the web page on the browser by obtaining data such as articles and images from this web server.

　However, on sites that develop globally services and popular sites, if access is concentrated only on the original web server, the quality of the service may be reduced, or the page is read when accessing from a distant area.It takes time to take time (the state in Fig. 1).

　CDN can improve this situation.

　I don't usually be aware of it, but as I can see from this Fastly failure, CDN is used by various sites.To briefly explain the CDN, it is a reverse proxy server distributed in various areas.

　The proxy server used in companies and other companies is used for communication to an unspecified number of destinations from a specific source, but the reverse proxy server is the opposite, communication from an unspecified number of source.Used to transfer to a specific server.

　More specifically, the communication to the original access destination is transferred to the CDN server using the DNS mechanism.

　For example, as shown in Fig. 3, to look at the web page, "https: // wwww is" https: // www..example.When you enter "com", the answer is "●●●" instead of returning the IP address of this server..map.fastly.The name of the CDN server (CNAME) such as Net (for Fastly) is returned.

　As a result, the PC will access the server owned by CDN operators, not the original web server.

　Then, if there is a cache on the CDN server (if the data has been accessed by other users before), send the web page from the cache, and if there is no cache, transfer to the original web server (original server).。It is a mechanism to cache the data again.

　CDNs are generally used on Web servers, but they can be used in various data, such as app distribution, video streaming, and updated program distribution, making it an indispensable service on the Internet.

　The main businesses include AKAMAI, Amazon CloudFront, CloudFlare, and CDNETWORKS.

　Fastly, which has become a hot topic this time, is a relatively new service founded in 2011, but the high functionality built based on the open source VARNISH is attracting attention, and it is only published on the company's web page in Japan.It is used on major sites such as the Nihon Keizai Shimbun, Mercari, Cookpad, and Ikyu.