X.25: It's Come a Long Way

The X.25 protocol was first standardized over a decade ago by the International Telegraph and Telephone Consultative Committee (CCITT). As a result of extensions made to the protocol,the field of application of X.25 has been greatly expanded. No longer a protocol used only in "X.25 networks," parts of the protocol are being used in Local Area Networks (LANs), in the emerging Integrated Services Digital Networks (ISDNs), and even in modems. X.25 has also become part of the work known as Open Systems Interconnection (OSI). This article describes the X.25 protocol briefly, discusses related protocol work, and shows how X.25 has been applied to the areas mentioned above.