Byzantine-fault-tolerant replication enhances the availability and reliability of Internet services that store critical state and preserve it despite attacks or software errors. However, existing Byzantine-fault-tolerant storage systems either assume a static set of replicas, or have limitations in how they handle reconfigurations (e.g., in terms of the scalability of the solutions or the consistency levels they provide). This can be problematic in long-lived, large-scale systems where system membership is likely to change during the system lifetime.
In this paper, we present a complete solution for dynamically changing system membership in a large-scale Byzantine-fault-tolerant system. We present a service that tracks system membership and periodically notifies other system nodes of membership changes. The membership service runs mostly automatically, to avoid human configuration errors; is itself Byzantine fault- tolerant and reconfigurable; and provides applications with a sequence of consistent views of the system membership.
We demonstrate the utility of this membership service by using it in a novel distributed hash table called dBQS that provides atomic semantics even across changes in replica sets. dBQS is interesting in its own right because its storage algorithms extend existing Byzantine quorum protocols to handle changes in the replica set, and because it differs from previous DHTs by providing Byzantine fault tolerance and offering strong semantics.
We implemented the membership service and dBQS. Our results show that the approach works well, in practice: the membership service is able to manage a large system and the cost to change the system membership is low.
In Existing System, replication enhanced the reliability of internet services to store the data’s the preserved data to be secured from software errors. But, existing Byzantine-fault tolerant systems is a static set of replicas. It has no limitations. So, scalability is inconsistency. So, these data’s are not came for long-lived systems. The existence of the following cryptographic techniques that an adversary cannot subvert: a collision resistant hash function, a public key cryptography scheme, and forward-secure signing key and the existence of a proactive threshold signature protocol.
In Proposed System, has two parts. The first is a membership service (MS) that tracks and responds to membership changes. The MS works mostly automatically, and requires only minimal human intervention; this way we can reduce manual configuration errors, which are a major cause of disruption in computer systems periodically, the MS publishes a new system membership; in this way it provides a globally consistent view of the set of available servers. The choice of strong consistency makes it easier to implement applications, since it allows clients and servers to make consistent local decisions about which servers are currently responsible for which parts of the service. The second part of our solution addresses the problem of how to reconfigure applications automatically as system membership changes. We present a storage system, dBQS that provides Byzantine-fault-tolerant replicated storage with strong consistency.
- Reliable Automatic Reconfiguration
- Tracking Membership Service
- Byzantine Fault Tolerance
- Dynamic Replication
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