Many corporate networks require web browsers (and often other types of network applications) which access an external network (like the internet) to use a web or application proxy. A proxy server makes requests on a client program’s behalf. In the case of web browsing, a user is typically told to specify some internal host on some ports (often other than the standard ports of 80/TCP and 443/TCP for HTTP and HTTPS, respectively) to access for intranet egress to the internet. Then this one proxy host is subsequently allowed out through the firewall instead of every client being allowed to connect directly. This is done to control and monitor user access but also to cache common content to improve performance.