 Multimedia content is transferred through Media Transfer Protocol (MTP); however, its proprietary MTP extensions ("MTPZ") place an interoperability barrier between the Zune and previous MTP-based software.The Zune software functions as management software for the device, a full media player application with a library, an interface to the Zune Marketplace, and as a media streaming server.Zune Software is used to sync with all devices with Zune functionality, including the Zune devices, Windows Phone 7, and Microsoft Kin.