Time_Accounting Mechanism Of Distributed Real_Time Systems Based On Message

Real_Time system is time_critical systems , It has been applied to many field, eg industry, business, aviation spaceflight and military affairs. Real_Time application is heading forward distributed systems . So , the researchs on real_time systems get especially importance .The communication rules between nodes are the base of networks applied in distributed systems. As an important communication mode between nodes in distributed real_time systems is rather difficult to ensure real_time requirement of message passing. At present , the real_time requirement of this kind of systems is usually satisfied by Clock Synchronization technique based on Global Clock (GC). The method of GC is not only complicated but limited in applicability ,It is merely suitable for time_based distributed real_time systems. For the distributed real_time which will be widely applied in future, It is a urgent problem to be solved how to realize real_time characteristic without GC. The detail discussion and main contribution are summarized as follows:One, about time_characteristic was analyzed in a distributed real_time systems, the paper pointed that real_time mechanism was required to ensure real_time demand of system.Two, the clock synchronization of each nodes in distributed real time system is implemented through message passing. although there is no accordant absolute time in each nodes, they could have accordant comparative time. according to that, propose a time accounting scheme based on message. without GC, we let the message carry the time requirement(deadline) of the real time tasks, and also account the passing time in message, by that we can make guidance on the processing of the message, and suffice the real time requirement of tasks. this scheme avoid the complexity of the clock synchronization, more easier to carry out ,at the same time it solve the problem of applicable limitation of GC's.Three, principle and realization of time_accounting mechanism were researched theoretically ,the distributed of the time elapse to message passing in the system was analyzed .According to the principle of time_accouning , the time_accounting was presented on the delay time in the process of message passing, and will achieve message prognostication, and a design idea was introduced to achieve time_accounting...