Résumé : This paper presents the implementation of the ORFA client. ORFA aims at providing an efficient access to remote file systems through high-speed local networks such as Myrinet. The ORFA client is a lightweight shared library that may be pre-loaded to override standard file access routines to allow remote file access for any legacy application. In ORFA, virtual file descriptors have been designed to support POSIX behavior such as file sharing semantics so that remote files may be accessed and manipulated as local files. Local file access routines may still be used without any incompatibility with other libraries that modify their standard behavior. Finally, a network abstraction layer has been implemented in ORFA to efficiently use asynchronous interfaces such as GM without suffering from memory registration requirements.