Timo Jokiaho

Using OpenAIS for building highly available session initiation protocol (SIP) registrar

Designing for continuous service is a challenge for every telecom application developer. There are various telecom platforms that provide frameworks to address this issue. However, these have proprietary interfaces and are often complex to develop new application. In this paper, we describe our experience with using open source cluster middleware, OpenAIS, for building a telecom application used in IP Multimedia subsystem. The telecom application is a Session Initiation Protocol (SIP) Registrar that keeps user location information In particular, we discuss important design and implementation aspects in making SIP registrar highly available. We also discuss important high availability state transitions, fault handling, application state synchronization. In the end, we share important lessons learned during design, implementation, and deployment.

Building highly available application using SA forum cluster: a case study of GGSN application

Most of the highly available applications are built on top of expensive cluster software with proprietary application interface and have problems with maintenance and enhancements. The SA Forum has standardized application interface for building highly available applications. This paper discusses our experience with early adoption of SA Forum specification both for implementation of a cluster as well as developing a real-world telecom application. This paper outlines steps to develop highly available application on a SA Forum based cluster using an element of 3G networks, GGSN, as a case study. Various design considerations such as building standby; synchronizing between active and standby; and handling switchover are discussed in detail. In addition, we have included the lessons that we learnt during development, integration, and testing to help prospective developers of complex real-time telecom applications.