Intel® oneAPI Collective Communications Library (oneCCL) Developer Guide and Reference
                    
                        ID
                        772609
                    
                
                
                    Date
                    6/30/2025
                
                
                    Public
                
            Transport Selection
oneCCL supports two transports for inter-process communication: Intel® MPI Library and libfabric*.
The transport selection is controlled by CCL_ATL_TRANSPORT.
In case of MPI over libfabric implementation (for example, Intel® MPI Library 2021) or in case of direct libfabric transport, the selection of specific libfabric provider is controlled by the FI_PROVIDER environment variable.