The refresh token flow applies when a Client application has access to a refresh token returned in a previous response to an authorization code request. The refresh token allows applications to skip the step that requires human interaction with the Identity Provider. This flow is initiated when the Client sends the refresh token to Authorization Service which validates it and returns an Access Token. A Client that saves the refresh token for later use shall use encryption or other means to ensure the refresh token cannot be accessed by unauthorized parties.
The complete flow is described in RFC 6749 Clause 6.
A requestType is not defined since support for refresh token is determined by checking the response to an authorization code request.