With 25 source licencees under its belt for Unix System V, Release 3.0 since its launch nearly a year ago, out of a European claimed customer base for System V of about 150, AT&T Unix Europe has announced Release 3.1. Basically a maintenance release, V.3.1 tidies up a few rough edges, and is said to improve performance as well as bringing in new facilities. After Remote File Sharing had been touted as the general Unix solution for distributed data access since its release with V.3, the rather unfortunate discovery was made that it relied on the assumption that the underlying transport layer could provide message boundaries, which restricted its use to certain transports. System V.3.1 is said to sport the new, transport-independent version of RFS, and also features RFS performance improvements with optional caching on RFS client systems. Several utilities have been rewritten, and other performance improvements include user area paging. And AT&T has, at last, begun to introduce internationalisation features to System V: it says that V.3.1 will handle 8-bit character sets, and different date/time formats. As expected when V.3.0 was released, it has taken a considerable time both for manufacturers to announce V.3 implementations, and for support for Streams-based protocol modules to appear. With suppliers now beginning to show TCP/IP implementations, a variety of others are under development from third parties including MS-Net and OSI/MAP, with OSI and TCP likely to appear in various board-level and in-kernel forms. AT&T also has plans for a higher level interface for applications than the current ISO layer 4-equivalent Transport Layer Interface. The key feature of this will be an application layer interface that combines features of IBM’s SNA LU6.2 and the ISO CASE; applications written to either will, thanks to Streams, be independent of the underlying protocols, but will be able to get at features of whatever is underneath – SNA services for instance. AT&T’s progress on this appears to be largely dependent on the work of standards bodies including ISO and X/Open; and it doesn’t appear to be just round the corner. One feature conspicuously still missing from V.3.1 is an AT&T-Sun Microsystems agreement on what to do about compatibility between RFS and Sun’s Network File System. The intention is that they should be able to coexist, and one prime area of incompatibility is at the virtual file system level: AT&T’s File System Switch, Sun’s Vnode. AT&T left FSS undocumented and liable to change, but the two companies still have not resolved the problem. Andy Rutter, technical director of The Instruction Set, which distributes the Sun product in Europe, said however that it had managed to implement versions of NFS that use the FSS for some customers.