Slotted-FIFO Communication for Asynchronous Distributed Systems

Communication protocols designed for database applications are not necessarily suitable for other applications, like multimedia communication, due to the former's requirement of reliable and ordered communication, and the latter's ability to withstand occasional losses and misordering of messages as long as real-time communication can be supported. This paper presents the slotted-FIFO communication mode that supports communication primitives for the entire spectrum of reliability and ordering requirements of distributed applications: for example, FIFO as well as non-FIFO, and reliable as well as unreliable communication. It provides communication with a run-time variable degree of reliability and/or ordering. Hence, the slotted-FIFO communication mode is suitable for applications that can work with relaxed reliability and/or ordering constraints such as multimedia applications. The protocol is simple and has low overheads. As FIFO ordering is not required for all messages, message buffering requirements are considerably reduced. Also, message latencies are lower. We demonstrate such advantages by means of a simulation study. A low overhead protocol implementing slotted-FIFO communication is also presented. The protocol incurs a small resequencing cost.