Within a single node it's just called DMA. RDMA is DMA over a network and RoCE is RDMA over Ethernet.
Sorry, but it certainly isn't--
https://docs.nvidia.com/cuda/gpudirect-rdma/index.html
The "R" in RDMA means there are multiple DMA controllers who can "transparently" share address spaces. You can certainly share address spaces across nodes with RoCE or Infiniband, but thats a layer on top
alt Hacker News
Sorry, but it certainly isn't--
https://docs.nvidia.com/cuda/gpudirect-rdma/index.html
The "R" in RDMA means there are multiple DMA controllers who can "transparently" share address spaces. You can certainly share address spaces across nodes with RoCE or Infiniband, but thats a layer on top