The present disclosure provides a source specific multicast service that maps multicast group addresses to corresponding source addresses. A boundary routing element can be configured to determine whether a received join request includes a mapped group address. If the join request does not include a mapped group address, boundary routing element can be configured to perform normal join request processing of the join request. If the join request includes a mapped group address, the boundary routing element can be configured to generate a corresponding source address using the mapped group address. The boundary routing element can also be configured to perform alternative join request processing as if the join request were an SSM join request that specified both a source address and a multicast group address.