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Consider the follow ing failur

[问答题]

Consider the follow ing failure model for faulty processors.Processors follow the protocol but might fail at unexpected points in time.When processors fail,they simply stop functioning and do not continue to participate in the distributed system.Given such a failure model,design an algorithm for reaching agreement among a set of processors.Discuss the conditions under which agreement could be reached.

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林呼

Assume that each node the following multicast functionality which we refer to as basic multicast or b-multicast.b-multicast(v) ：node simply iterates through all of the nodes in the system and sends an unicast message to each node in the system containing v.
Also assume that each node performs the following algorithm in a synchronous manner assuming that node i starts with the value vi.
At round 1,the node performs b-multicast(vi).
In each round,the node gathers the values received since the previous round,computes the newly received values,and performs a b-multicast of all the newly received values.
After round f + 1,if the number of failures is less than f,then each node has received exactly the same set of values from all of the other nodes in the system.In particular,this set of values includes all values from nodes that managed to send its local value to any of the nodes that do not fail.
The above algorithm works only in a synchronous setting and the message delays are bounded.It also works only when the messages are delivered reliably.

发表于 2018-03-25 10:15:03 回复(0)