Custom port mapping involves mapping the backend resource or server to a port number at the SMA appliance. The application listens on this port and all HTTPS traffic received on it is terminated at the appliance. A new HTTP request is made to retrieve the mapped backend resource. The HTTP reply is transmitted using plain text to facilitate translation of absolute URLs. URL rewriting is not used. When using custom port mapping, any firewalls in the network must be configured to keep the specific ports open. Custom port mapping does not require installation of a client agent, and works with any Web browser.