Answer - A list of essential components used in WCF: Service class The service runtime layer contains the behaviors that occur only during the actual operation of the service, that is, the runtime behaviors of the service. Throttling controls how many messages are processed, which can be varied if the demand for the service grows to a preset limit. Endpoint WCF Service is a program that exposes a collection of the endpoints. Each Endpoint is a portal for communicating with the world. All the WCF communications are taken place through the endpoint. An endpoint consists of three components. Hosting Environment A service must be hosted in some process. A host is an application that controls the lifetime of the service. Services can be self-hosted or managed by an existing hosting process.