Shared Memory Communications - Direct Memory Access
Shared Memory Communications - Direct Memory Access (SMC-D) uses internal shared memory (ISM) for communication between two SMC capable peers that are located on the same central processor complex (CPC). The communicating peers, such as TCP/IP stacks, dynamically detect the shared memory capability by using traditional TCP/IP connection establishment flows. The shared memory enables the TCP/IP stacks to switch from TCP network flows to more optimized direct memory access flows that use ISM.
As shown in Figure 1, SMC-D enables two virtual servers that support ISM to logically share memory. When a virtual server that supports ISM detects that a TCP connection partner also supports shared memory communications by using ISM, the connection is transparently and dynamically switched to use SMC-D protocols. The applications are unaware of the use of shared memory for communications.
