Diploma Thesis

By reducing the complexity of distributed systems through separation, and defining formal operational work-flows, the reliability of VoIP services can be improved heavily. The existence of popular Open Source Voice-over-IP (VoIP) frameworks based on the Session Initiation Protocol (SIP) allows service providers to easily deploy feature-rich telecommunication systems. However, despite the rapidly growing spread of VoIP services, a lot of providers still face problems when trying to establish a high level of reliability of these services. In order to determine potential causes for availability degradation, traditional telephony and Internet services as reference models for distributed communication systems are analyzed according to their reliability and scalability. Since human errors are found to account for the majority of system outages, guidelines for designing and operating a complex distributed environment are defined. Also the usage of SIP in typical network topologies raises problems when it comes to scaling a VoIP service. Therefore a practical approach for providing a highly modular and thus scalable system is presented.

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