Music, photos and videos can be played from standard USB mass storage devices, Xbox 360 proprietary storage devices (such as memory cards or Xbox 360 hard drives), and servers or computers with Windows Media Center or Windows XP with Service pack 2 or higher within the local-area network in streaming mode. As the Xbox 360 uses a modified version of the UPnP AV protocol, some alternative UPnP servers such as uShare (part of the GeeXboX project) and MythTV can also stream media to the Xbox 360, allowing for similar functionality from non-Windows servers. This is possible with video files up to HD-resolution and with several codecs (MPEG-2, MPEG-4, WMV) and container formats (WMV, MOV, TS).
What component of the Xbox 360 permits the use of alternative UPnP servers to stream media to the console?
modified version of the UPnP AV protocol