Static Internet multicast

IP multicasting (Cheriton and Deering, 1985) appears to achieve a level of simplicity by extending the IP unicast addressing model (historically the class A, B, and C net numbers) from the mask and longest match schemes of CIDR (Braun et al. 1993), with a new classful address space, class D. The routing systems have been also built in a deceptively simple way in one of three manners-either broadcast and prune, destination list based tree computation or single centered trees. The multicast service creates the illusion of a spectrum that one can tune in to, as an application writer. Thus, many have seen the multicast pilot service, Mbone, as a worldwide Ethernet, where simple distributed algorithms can be used to allocate "wavelengths" and advertise them through "broadcasting" on a channel associated with a spectrum. These three pieces of the picture have tempted people to construct a distributed architecture for a number of next level services that cannot work at more than a modest scale, since they ignore the basic spirit of location independence for senders and receivers of IP packets. The problem is that many of these services are attempting to group activities at source, when it is only at join time that user grouping becomes apparent. This memo proposes approaches to solve some current multicast problems rather statically with DNS (Postel 1994) and the URL based approach, and avoid the pitfalls of trying to use address allocation to implement traffic aggregation for different sources or aggregation of multicast route policy control through control of such aggregated sources.