DMS and DMP are the most important elements for DLNA. Of course, some DMPs would function as DMC.
For example, you could have your
WD TV Live Plus connected to the share network for your Windows 7 PC. Windows 7 is DLNA compliant. Then stream videos from PC to WD TV Live Plus via network, instead of copying files to external hard drive of WD TV Live Plus.
It saves you from getting messy cables when you get several DLNA devices.