The presentation is about designing and implementation of geographical redundant Voice over IP systems with the Kamailio SIP router. It goes through an overview about the 1&1 voice over IP backend, some performance requirements for carrier grade VoIP networks and real-world measurements.
Then are some key concepts for building a geographical redundant system are presented. This are for example partitioning of the user base and network load with different means like anycast IP and means of maintaining a shared database state for subscriber data and registration information. Finally some common problems in building bigger VoIP clusters and solutions approaches are discussed.