Research On Checkpointing In Mobile Computing Environment And Modeling With Petri Nets

Advancement in wireless networking and portable devices is revolutionizing the way individuals and businesses view computing. Mobile computing is expected to becoming the norm in the near future. People can move to anywhere while keeping connect to the network in mobile computing environment, which promote many new distributed applications to come into being. However, the property of mobility causes mobile computing system lack of reliability. It is important to provide fault tolerant measures for mobile computing system to make its success.Checkpointing and rollback recovery is the common fault tolerant measure in mobile computing environment. After discussing the sorting and comparison of checkpointing protocols, this paper developed two checkpointing algorithm, HMB protocol and MNLC protocol, according to whether the PWD assumption exist.HMB is a checkpointing protocol based on log. It is different from the current approaches, which take checkpoints periodically without regard to the mobility rate and message arrival rate. In HMB, the checkpointing interval is completely determined by the hand off rate and message arrival rate. HMB achieves a better balance between faultless cost and instant recoverability.MNLC protocol is a checkpointing protocol based on coordinated checkpoint, which features in finding out the real checkpoint dependant processes. By means of communication records and send infect record, which are two kinds of message logs recorded in normal message communication, MNLC enable the minimal processes take part in checkpointing and rollback. In addition, MNLC assign many roles in checkpointing to the MSS in stead of MH, which approves the low cost of MNLC.In order to evaluate the performance of designed protocols, this paper discussed the modeling of MNLC and HMB protocols by Petri Nets and gained their performance property respectively.