SSM (Source Specific Multicast) defines an IP multicast session with a single multicast source S, known by the set of multicast receivers. At the network level, only S is allowed to send in the channel identified by (S,G). G is generally allocated by a local process running on the host having the IP address S. (S,G) is a channel identifier where groups subscribe specifically with an SSM capable host to router protocol like MLD version 2. We focus here only on the routing part of SSM, i.e. how the source specific multicast tree is built between SSM receivers and the source. We describe an end-host solution which enables multi-source sessions over SSM only networks.