Connectionless data transmission

The increasingly familiar and ubiquitous Reference Model of Open Systems Interconnection, currently being considered by the International Organization for Standardization (ISO) as a Draft International Standard (DIS), is based on the explicit assumption that a "connection" -- an association between two or more communication entities, possessing certain characteristics over and above those possessed by the entities themselves - is required for the transfer of data in an Open Systems Interconnection (OSI) environment. Although the connection-oriented model of communications behavior has proven to be an extremely powerful concept, and has been applied successfully to the design and implementation of protocols and systems covering a wide range of applications, a growing body of research and experience suggests that a complementary concept - connectionless data transmission - is an essential part of the Open Systems Interconnection architecture, and should be embraced as such by the OSI Reference Model. This paper explores the concept of connectionless data transmission and its relationship to the more familiar concepts of connection-oriented data transfer, developing a rationale for the inclusion of the connectionless concept in the Reference Model as an integral part of the standard description of the OSI architecture.