Structure and Flexibility for Fieldbus Messaging

Link layer Application Layer Application process Controller or update operations. the protocol allows a large span of applications and network speed/response disparities to be handled. There is a basic asymmetry in the model that reflects the actual implementation of Fieldbus applications. Most Fieldbus applications have a controller or user of information (client) requesting the transmitter or other source of information or services (server) to perform some application specific function (e.g. report a process measurement reading). There is no restriction on the roles a device may play, provided only that the appropriate link laver services are available. A device mav function as either or both client and server. A key feature of the protocol is its use of the notion of statelessness in field devices acting as servers in order to make it easier to design and maintain protocol implementations in potentially unreliable communications environments. This ",ill help avoid various subtle failures that are possible in data transfer between the host and the field device. All requests to a field device should be self-contained so that a