A quorum-consensus replication method for abstract data types
ACM Transactions on Computer Systems (TOCS)
Hierarchical Quorum Consensus: A New Algorithm for Managing Replicated Data
IEEE Transactions on Computers
Time, clocks, and the ordering of events in a distributed system
Communications of the ACM
WECWIS '00 Proceedings of the Second International Workshop on Advance Issues of E-Commerce and Web-Based Information Systems (WECWIS 2000)
Design and evaluation of a continuous consistency model for replicated services
OSDI'00 Proceedings of the 4th conference on Symposium on Operating System Design & Implementation - Volume 4
Maximum availability server selection policy for efficient and reliable session control systems
IEEE/ACM Transactions on Networking (TON)
ISAS'04 Proceedings of the First international conference on Service Availability
Probabilistic models for access strategies to dynamic information elements
Performance Evaluation
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The Session Initiation Protocol has been chosen for controlling multimedia sessions in the IMS part of UMTS infrastructures. In such networks, availability is crucial and the integration of SIP with a fault-tolerant solution, often based on a replication technique, has become necessary. Because the replicated stateful servers are deployed in distributed networks, state inconsistency may be introduced. Mechanisms have been proposed, which aim at keeping the inconsistency level below a certain threshold by introducing an adaptive delay before the states are committed. The effectiveness of those adaptive mechanisms depends on the accuracy of the inconsistency evaluation during the system operation. In this context, the careful definition of a practically measurable inconsistency metric is necessary in order to benefit from those mechanisms while minimizing their impacting on performance. This paper discusses the relevance of different inconsistency definitions and suggests a common model in which the inconsistency metrics are broken down into a set of measurable and/or analytically derivable contributing factors. We analyze the validity of this evaluation approach with results obtained in a prototype implementation of a 3GPP IMS call control system integrated in a distributed fault-tolerant architecture, so-called RSerPool, for the example of instant message sessions between users.