It is in general recognized that IP multicast routing protocols are fairly complex and non-scalable and its property to make it work ideally requires additional maintenance cost to network administrators and operators. Hence although the Internet community has been doing a significant amount of research works on IP multicast over the last decade and most router vendors already support basic IP multicast routing protocols, there are still deployment problems in the Internet. In this document, we analyze the difficulties of traditional many-to-many communication and the benefit of one-to-many or few-to-many communication. While the former communication model called Any-Source Multicast (ASM) does not require the source address specification, the later communication model called Source-Specific Multicast (SSM) requires the source address specification, when an application joins to the group. We mainly study the difference of the routing protocols between these models.