Distributed Agents For Remote Service Reconstruction In Field-bus and IP networks

Computing IP networks use the TCP/IP protocol extensively for connection-oriented service access, and UDP/IP is used for best-effort connectionless data transfer. Commonly used RPC mechanisms like Java RMI, IIOP and CORBA use TCP/IP which has connection set-up and management overheads. For systems with high speed and high frequency RPC (Remote Procedure Calls), connection management overheads can affect the system performance and overload the server. Such is the case with a number of measurement and controls engineering applications where the field devices communicate continuously with the field bus server, at a high frequency. The control software for such systems have to consider the real time performance issues, load balancing and fault tolerance. Moreover, the plug-nplay field-bus Human Machine Interfaces (HMI) require reconfiguration at every node they are installed and therefore automated re-configuration and re-construction could save time and effort for measuring and monitoring processes. To reduce the communication overheads caused due to connection management, RPC over UDP/IP can be used as an alternative to RPC over TCP/IP, for high frequency RPC calls. In addition, the server load can be sufficiently reduced by transferring the remote service parameters to the client end (for re-construction), instead of executing the entire service at the server end for each client. Reconstructing the remote service at the client end by using these service parameters, aided with RPC implementation over datagrams, can improve the system performance and help perform load balancing and fault tolerance tasks. Keywords-Distributed Agents, Field-bus, RPC, HMI, RPC over UDP