Applications, programming languages, and libraries that leverage sophisticated network hardware capabilities have a natural advantage when used in today¹s and tomorrow’s high-performance and data center computer environments. Modern RDMA based network interconnects provides incredibly rich functionality (RDMA, Atomics, OS-bypass, etc.) that enable low-latency and high-bandwidth communication services. The functionality is supported by a variety of interconnect technologies such as InfiniBand, RoCE, iWARP, Intel OPA, Cray¹s Aries/Gemini, and others. Over the last decade, the HPC community has developed variety user/kernel level protocols and libraries that enable a variety of high-performance applications over RDMA interconnects including MPI, SHMEM, UPC, etc. With the emerging availability HPC solutions based on Arm CPU architecture it is important to understand how Arm integrates with the RDMA hardware and HPC network software stack. In this talk, we will overview Arm architecture and system software stack, including MPI runtimes, OpenSHMEM, and OpenUCX.