Causally ordered message delivery in mobile systems

There is a growing trend in using mobile computing environments for several applications, and it is important that such mobile systems are provided with adequate support both at the systems level and at the communication level. Causal ordering is a useful property, particularly in applications that involve human interactions. We present three algorithms for causal ordering in mobile systems. The first algorithm handles the resource constraints of the mobile hosts. But the system is not easily scalable and is not graceful in hosting disconnections and connections. The second algorithm eliminates the above disadvantages at the cost of inhibiting some messages. The third algorithm is a trade-off between the first two algorithms.