This chapter describes, using the technology background terminology defined in the previous chapter, the most interesting scenarios the user may address when building an IP telephony infrastructure. The scenarios here detailed address topics with increasing complexity (from a long-distance least cost routing scenario to a fully integrated IP telephony - videoconferencing one). The aim of this chapter is to provide the user with both a high level overview of each scenario and with motivations on why they are to be deployed. Each scenario is analyzed from the user needs point of view and is described architecturally giving an example of integration.