A startup function sets up the hosting environment by registering a set of middleware with the application. For each request, the application calls each of the the middleware components with the head pointer of a linked list to an existing set of handlers. Each middleware can add one or more handlers to the request handling pipeline by returning a reference to the handler that is the new head of the list. Each handler is responsible for remembering and invoking the next handler in the list.

## Terminology

• **OWIN** – An abstraction between Web servers and framework components.

• **Middleware** – A function called in the OWIN pipeline.

To configure OWIN authentication, set the authentication type in the _system.web_ section of _web.config_.

To configure OWIN authentication, create a _Startup_ file in your project that handles the configuration of the different authentication middleware.