Open Network Computing (ONC) is an operating environment developed by Sun Microsystems that serves as an interface to all resources on a network. It is the model of distributed computing
supported by most Unix environments. In transport-oriented layers 1 through 4, ONC computing uses the TCP/IP, SPX/IPX, or OSI transport protocols. Transport services are accessed through the Transport Layer Interface (TLI). Of the application-oriented layers, only the application layer is used for Remote Procedure Call (RPC) and the Network File System (NFS). This is used to handle files that are distributed across the remote nodes. Remote Procedure Call (RPC) is used to transfer the distributed files.