Core Based Tree (CBT) Multicast - Architectural Overview and Specification

groups may also distribute working documents as Internet Drafts. Internet Drafts are draft documents valid for a maximum of six months. Internet Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material or to cite them other than as a \working draft" or \work in progress." Abstract CBT is a new architecture for local and wide-area IP multicasting, being unique in its utilization of just one shared delivery tree, as opposed to the source-based delivery tree approach of existing IP multicast schemes, such as DVMRP 6] and MOSPF 15]. The primary advantages of the CBT approach are that it ooers more favourable scaling characteristics in certain situations than do existing multicast algorithms, and is independent of whichever underlying unicast routing protocol is operating. This draft describes the CBT protocol in detail, as well as the CBT architecture. The deenition of a new network layer multicast protocol has also meant that it has been possible to integrate an enriched functionality into multicast that is not possible under other IP multicast schemes. For example, CBT ooers a potential solution to \anycasting" 14], and it has been possible to integrate security features into the CBT protocol. Besides CBT's capability to authenticate tree-joining host's and routers, optional in-built protocol mechanisms provide a scalable solution to the multicast key distribution problem 10]. CBT has been designed to interoperate with existing IP multicast techniques, as well as other new IP multicast proposals, such as PIM 17]. Interoperation will be discussed in detail. Some open and, as yet, unresolved issues are also discussed.