The Intermediary is the architectural component that receives new certificate requests from clients and submits them to the Server Engine. The intermediary is composed of two parts, the intermediary application that performs actions on behalf of clients, and the Certificate Server client interface (CertCli.dll) that handles communications between the intermediary application and the server engine.
Intermediaries can be written to handle certificate requests from different types of clients and across multiple transports. Microsoft® Internet Information Server is an intermediary that provides support for clients over HTTP. Intermediaries can also check on the status of a previously submitted request and obtain the Certificate Server's configuration information.