End-to-End Network Reliability Modeling of Enterprise VoIP Services

Practical reliability models are developed to support the engineering of carrier-class networks that provide VoIP service to enterprise customers. The focus is on end-to-end measures of service reliability. The paper first describes the typical architecture of large-scale carrier-class VoIP networks, the message flows that exist therein, and use case variations that arise in practice. Reliability measures of interest are then defined and models are developed in terms of the call flows and element reliabilities. The failover and repair mechanisms that may be employed in the various protocol layers are also surveyed. An example analysis illustrates the modeling of a particular use case. The developed models provide a convenient practical means to estimate end-to-end VoIP service reliability prior to field trials or network deployments. Such proactive modeling is an important step in the planning and engineering of new VoIP networks