The fault tolerance mechanism of the PIM-SM IP multicast routing protocol is investigated in order to be able to model it. The analysis is done by playing different fault scenarios on a mesh topology multicast test network built up by XORP routers in a virtualized environment. Different parameters of the PIM-SM and the OSPF protocols are examined if they influence and how they influence the outage time of an IPTV service. The results of the experiments provide important factors for building a formal model of the service outage time of an IPTV service. © 2012 EUROSIS-ETI.