Yes, the DTH-P1 can be plugged on an ATCA node slot. To do so, 2 jumpers should be changed to "NODE"position (J26 at bottom front position on the card, J45 back middle position on card).
It is written on board "NODE"or HUB".

In this configuration, the ethernet connection can be done from the backplane (if you have a switch on the HUB1 slot)

The DTH-p1 has a switch on board, but it doesn't distribute the 1Gb ethernet to the nodes.
This switch has only 5 ports: RJ54 (at front panel), IMPC, ComExpress and the 2 shelf managers.

The DTH should be installed in the HUB slot (1).

For basic tests a loopback MPO is provided and has to be plug on the MPO font panel