X.25 — the fulcrum for network standardization

Abstract

The synchronous interface to packet switched data networks defined by the CCITT's X.25 recommendation has been in practical use for approximately ten years. Conceived and introduced amidst controversy, it has, despite its defects, more than stood the test of time. The recommendation's early history is briefly outlined, followed by a review of its development to the present day in some detail. In a wider context, the international acceptance of the standard has, in turn, contributed greatly to the success of packet switching. This wider influence is also discussed, as is the influence of X.25 in other related areas, whether Common Channel Signalling (CCS), Integrated Services Digital Networks (ISDN), Asynchronous Time-Division Switching (ATDS) or the whole Open Systems Interconnection Reference Model. X.25 is the fulcrum which has enabled the telecommunication administrations of the world to lever the computer manufacturers and users into ever greater conformance to international standards in all aspects of data networks.