In windows Deployment services there are three server modes (roles). These modes determine the image format, boot environment and administration experience. To check the operating mode in WDS, from the command prompt WDSUTIL /get-server /show:config , above command output displays the server mode(role).
In native mode we can deploy only .wim images only. To enable native mode, install and configure WDS on a server that has RIS Installed but should not configure it. If already configured need to uninstall and reinstall before configuring windows deployment services.
Legacy mode environment used generally, if you do not have windows vista in the environment. For this mode install and configure RIS and then install Windows deployment services (but should not configure).
In Mixed mode environment we can deploy RISETUP and RIPREP images type using OSChooser and also can deploy .wim based images by using WDS management tools. For mixed configuration, configure Windows deployment services on existing RIS configuration.