| The structure of ForCES router contains a Control Element (CE) which controls and manages hundreds of Forwarding Element (FE). There are transactions in the ForCES router, such as routing and resource reverse. The traditional transaction model uses strictly two stages submit agreement, that is when any subtransaction fails, the whole transaction has to been rolled back to the state before the execution. And while all of the subtransactions executed successfully, the the transaction can be allowed to commit. Such all commit or all not commit which is called All or Not stragegy affects the system performance and also the successful rate. So based on the traditional transaction model, the predecessors proposed the nested transaction model. In this model, it only rolls back the failed subtransaction and reserve the state of the successful subtransactions, after that, it will choose an alternative to continue the transaction execution.According to the existing transaction model, this paper has done the following works:firstly, it proposes the dynamic nested transaction model that is to search for a alternative subtransaction dynamically:when a node FE fails, find out the two neighbor nodes of this FE, and try to find out another road between these two nodes, if it has one. then execut it. if not, then roll back the whole transaction. Secondly, the paper have made stract derivation by matimatical formulars and proofed the superiority of the dynamic nested transction. Besides this, it has also done some computer simulations in order to make the result more intuitive. Thirdly, this paper also studied the two deployment mode of transactions which is called the unicast and multicast and discusses the advantages and disanvantages of these two methods, also, it proposes a best way. At last, based on the mechanism description of the transaction in the ForC'ES agreement, the paper has made a design for the transaction flat transaction model and dynamic nested transaction model. |
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