Existing multicast routing mechanisms were intended for use within regions where a group is widely represented or bandwidth is universally plentiful. When group members, and senders to those group members, are distributed sparsely across a wide area, these schemes are not efficient; data packets or membership report information are occasionally sent over many links that do not lead to receivers or senders, respectively. Wehave developed a multicast routing architecture that efficiently establishes distribution trees across wide area internets, where many groups will be sparsely represented. Efficiency is measured in terms of the state, control message processing, and data packet processing, required across the entire network in order to deliver data packets to the members of the group. Our Protocol Independent Multicast (PIM) architecture: (a) maintains the traditional IP multicast service model of receiver-initiated membership; (b) can be configured to adapt to different multicast group and network characteristics; (c) is not dependent on a specific unicast routing protocol; and (d) uses soft-state mechanisms to adapt to underlying network conditions and group dynamics. The robustness, flexibility, and scaling properties of this architecture make it well suited to large heterogeneous inter-networks.

Multicast trees can be shared across sources (shared trees) or may be source-specific (shortest path trees). Inspired by recent interests in using shared trees for interdomain multicasting, we investigate the trade-offs among shared tree types and source specific shortest path trees, by comparing performance over both individual multicast group and the whole network. The performance is evaluated in terms of path length, link cost, and traffic concentration. We present simulation results over a real network as well as random networks under different circumstances. One practically significant conclusion is that member- or sendercentered trees have good delay and cost properties on average, but they exhibit heavier traffic concentration which makes them inappropriate as the universal form of trees for all types of applications. Keywords: Multicast, Routing, Scalability, Center Placement Strategy 1 Introduction Multimedia communication is often multi-point and has contributed to the dem...

Traditional multicast routing mechanisms (e.g. DVMRP and MOSPF [1, 2]) were intended for use within regions where groups are widely represented or bandwidth is universally plentiful. When group members, and senders to those group members, are distributed sparsely across a wide area, these schemes are not efficient; data packets or membership report information are periodically sent over many links that do not lead to receivers or senders, respectively. This characteristic lead the Internet community to investigate multicast routing architectures that efficiently establish distribution trees across wide-area internets, where many groups are sparsely represented and where bandwidth is not uniformly plentiful due to the distances and multiple administrations traversed. Efficiency is evaluated in terms of the state, control message processing, and data packet processing required across the entire network in order to deliver data packets to the members of the group.

. Multicast trees can be shared across sources or may be source-specific. Inspired by recent interests in using shared trees for interdomain multicasting [BFC93] [WLE + 92], this paper investigates the trade-offs among different algorithms and tree types. Because of the dynamic nature of graphs, only worst case delay bounds can be calculated using analytical methods. We present simulation results over random graphs that demonstrate the performance of these trees, under different circumstances. We evaluate the performance in terms of path length, link cost, and traffic concentrations. Draft submitted to INFOCOM'94 1 Introduction Point-to-multipoint communications will play a critical role in future computer networks. The problem of computing the optimal multicast path, in the shape of a tree or a group of trees, has many potential solutions; however, to date there have not been systematic comparisons among the different solutions. Today's multicast applications are prima...

Existing multicast routing mechanisms were intended for use within regions where a group is widely represented or bandwidth is universally plentiful. When group members, and senders to those group members, are distributed sparsely across a wide area, these schemes are not efficient; data packets or membership report information are occasionally sent over many links that do not lead to receivers or senders, respectively. We have developed a multicast routing architecture that efficiently establishes distribution trees across wide area internets, where many groups will be sparsely represented. Efficiency is measured in terms of the state, control message processing, and data packet processing, required across the entire network in order to deliver data packets to the members of the group. Our Protocol Independent Multicast (PIM) architecture: a) maintains the traditional IP multicast service model of receiver-initiated membership; b) can be configured to adapt to different multicast grou...