Windows Process Activation Service listens for messages on behalf of Windows Communication Foundation (WCF) services and ...

Windows Process Activation Service listens for messages on behalf of Windows Communication Foundation (WCF) services and starts the appropriate service when a message is received—even when the WCF services are not running. WCF services start automatically, and they run only when they are processing messages. This saves processor and memory resources so that you can run more services on a single server. Install Windows Process Activation Service with the protocols that your WCF services use. These protocols can include Hypertext Transfer Protocol (HTTP), Message Queuing, TCP/IP, and named pipes.