scope:

This standard is applicable to transportation related devices that must operate in a point-to-point configuration where exactly two devices (called peers) are connected by a logical Physical Layer communications link. As a subnetwork profile, this document specifies a set of protocols and standards applicable to the Data Link and Physical layers of the Open Systems Interconnect (OSI) Basic Reference Model. The Subnet Profile for the Point-to-Point Protocol over RS-232 is intended to provide an interoperability standard for the Physical and Data Link Layer aspects of communications in transportation related devices for dialed-up circuits.

The protocol stack described in this document is appropriate for the reliable exchange of data between processing equipment on switched data networks. The primary feature of this profile is reliable data transfer with security between directly connected devices.