In this paper we describe a P2P network that is designed to support VoD services. This network is based on a video file sharing mechanism that classifies peers according to the window (segment of the video) that they are downloading. Such classification allows identifying peers that are able to share windows among them, so one of our major contributions is the definition of an efficient and easy-to-implement video file sharing mechanism. Considering that cooperation among peers can be insufficient to guarantee an appropriate performance of the system, we also propose that the P2P network must be assisted by upload bandwidth from servers; we complement this idea by defining a highly efficient resources distribution scheme that prioritizes peers that are in windows with resources scarcity (we called it Prioritized Windows Distribution scheme). Given the above described system and on the basis of a fluid model and a Markov chain, we developed a methodology that allows selecting the design parameters values of the network (e. g. windows sizes and minimum servers upload bandwidth), that satisfies a set of target values for QoE parameters (e. g. MOS as a function of initial delay).