In the spring of 1988, AT&T took the standardization a step further. First, it collaborated with SCO to merge System V and Xenix into System V/386. Next, it sought collaboration with Sun Microsystems (vendor of the 4.2BSD derivative SunOS and its Network File System) to merge System V, BSD/SunOS and Xenix into a single unified Unix, which would become System V Release 4. AT&T and Sun, as UNIX International (UI), acted independently of X/Open and drew ire from other vendors, which started the Open Software Foundation to work on their own unified Unix, OSF/1, ushering in a new phase of the Unix wars.