Fastest ipc which stands for Inter Process Communication is Shared memory because the data is not copied from one address space to another, memory allocation is done only once, and syncronisation is up to the processes sharing the memory. Also due to minimal overhead. Overhead is generated whenever we make a call to another function. Be it a kernel or library. If our IPC makes no calls to any other function, then we have done away with a large bottleneck. Shared memory IPCs have no requirement for third party function calls.