I have tested the new Blackmagic nodes with an Ultrastudio 4k and they work perfectly. I've only done the test as input.
If you change the "Set time" in the node "Play movie" you can restart the video playback. In the composition I attach I restart by clicking on the window.
I have some work with IP cameras and I use some apps to capture the stream and then pass it to syphon.
There are cameras that have the option to choose between two protocols: http and rtps. There are also different codecs for streaming: MJPEG, H.264, ...
If you use the HTTP protocol and MJPEG encoding, there are two applications you can use to convert the stream to a syphon feed.
If you use the RTSP protocol you can use:
I hope it can be of help.