Network layer based redundancy for time-critical VoIP applications

Voice over Internet protocol (VoIP) applications are making their way into safety-critical environments. If voice data has to be transmitted in such environments, the connection must not fail and the network has to recover quickly. Additionally, the use of specialized systems that are tailored to a certain application is not a preferred solution. Instead, the use of commercial-off-the-shelf (COTS) hard- and software is required. This paper discusses the use of standardized hard- and software as well as network protocols to allow failover times within the range of milliseconds. A redundant end-system and its network coupling are presented. The Layer 3 protocol OSPF and the combination of OSPF with the protocol-independent Hello protocol BFD are investigated to fulfill the requirements. The tests and the achieved results show a significant reduction of the convergence time.