The application server must be configured to mutually authenticate connecting proxies, application servers or gateways.

Application architecture may sometimes require a configuration where an application server is placed behind a web proxy, an application gateway or communicates directly with another application server. In those instances, the application server hosting the service/application is considered the server. The application server, proxy or application gateway consuming the hosted service is considered a client. Authentication is accomplished via the use of certificates and protocols such as TLS mutual authentication. Authentication must be performed when the proxy is exposed to an untrusted network or when data protection requirements specified in the system security plan mandate the need to establish the identity of the connecting application server, proxy or application gateway.