SMC memory buffers

Each stack locally allocates memory for an SMC memory buffer to receive inbound data that uses SMC communications. An SMC memory buffer that is used for SMC-R communications is called a remote memory buffer (RMB), and an SMC memory buffer that is used for SMC-D communications is called a direct memory buffer (DMB). The sending operating system places TCP socket application data directly into the memory buffer that the receiving stack assigns to receive data for a TCP connection. The receiving stack then copies the data from the memory buffer into the receive buffer of the receiving socket application.

A memory buffer is partitioned into elements of equal size, and each element is associated with a single TCP connection. Direct memory buffers are partitioned into direct memory buffer elements (DMBEs), and remote memory buffers are partitioned into remote memory buffer elements (RMBEs). In the Connection Layer Control (CLC) messages during rendezvous processing, each peer communicates the location of its local DMBE, or its RMBE and a remote key, to allow remote access to the memory buffer. The remote host has write access and the local host reads the data for passing to the socket application.