[network planning] 2.2.4 Web cache / proxy server

This article is based on 《 computer network —— top-down approach 》 A Book

Web cache / proxy server

Web Buffer Also known as proxy server He is able to represent the source Web Server to meet HTTP Requested network entity . The proxy server has its own disk storage space , And save a copy of the recently requested object in storage .

You can configure a proxy server for your browser , When the browser accesses the website , It will first look for the requested object in its proxy server . If so, the object will be returned directly from the proxy server ; without , The proxy server will open a connection to the original server of the object TCP Connect , And ask the source server for the object that does not exist , When the proxy server receives the response message , The proxy server will store a copy in the local space , And then send the object to the request source .

There are two reasons to deploy a proxy server ：

1. Proxy server can greatly reduce the response time to customer requirements . For example, we can download directly Github The content on will be slow , If the proxy server of Tsinghua University is configured , Download much faster . The reason is simple , We are directly connected to Github The physical distance and network distance of overseas servers are longer than those connected to Tsinghua University , Therefore, it is better to obtain a copy from the proxy server of Tsinghua University than to connect directly Github Server downloads are much faster . Even if there is no copy of this object on the proxy server of Tsinghua University , The proxy server can also quickly request from the server through the high-speed link between the servers Github Download the corresponding object from the server .
2. The proxy server can also reduce the traffic to the source server . hypothesis 《 Interstellar through 》 Only Guangzhou has the film source , All the people in Guangdong will go to Guangzhou to see 《 Interstellar through 》, It is bound to be overcrowded , By distributing copies of the film to prefecture level cities , Then people can go to prefecture level cities to watch movies , Instead of going directly to Guangzhou to see . The same goes for proxy servers . Allocate requests from the source server by building multiple proxy servers , It can reduce the traffic of accessing the source server .