Abstract: In this paper, we study a multi-service Connection Admission Control CAC policy and we derive the corresponding Resources Allocation RA mechanism to access the Up/Down Link UDL in a Low Earth Orbit LEO satellite constellation used as an access network to a mobile terrestrial network. We propose the usage of a trunk reservation policy for bandwidth reservation that allows the network to root the call on the satellite where the blocking probability is minimum. In our study, we assume that the network handles three types of call: real time voice calls, non real time data calls with guaranteed bandwidth and non real time elastic data calls. A Markovian modelling approach is used to analyse the bandwidth occupation and derive the analytical model for the RA scheme.