Ring-buffer layout of a single Handler. The particles[ ] array is a circular buffer; dark cells are occupied slots in the region from ﹩{\mathtt{head}}\,\mathrm{mod}\,{\mathtt{buffsize}}﹩ to ﹩{\mathtt{tail}}\,\mathrm{mod}\,{\mathtt{buffsize}}﹩. Two RDMA-registered memory regions expose the particle data and the [head, tail] counter pair, respectively. Because each Handler has exactly one sender and one receiver (SPSC), no locks are required on the transfer path.