Routing in overlay multicast networks

Multicast services can be provided either as a basic network service or as an application-layer service. Higher level multicast implementations often provide more sophisticated features, and can provide multicast services, where no network layer support is available. Overlay multicast networks offer an intermediate option, potentially combining the flexibility and advanced features of application layer multicast with the greater efficiency of network layer multicast. Overlay multicast networks play an important role in the Internet. Indeed, since Internet service providers have been slow to enable IP multicast in their networks, Internet multicast is only widely available as an overlay service. This paper introduces several routing algorithms that are suitable for overlay multicast networks and evaluates their performance. The algorithms seek to optimize the end-to-end delay and the interface bandwidth usage at the routing sites within the overlay network. The interface bandwidth is typically a key resource for an overlay network provider, and needs to be carefully managed in order to maximize the number of sessions that can be served. The simultaneous optimization of both delay and bandwidth is an NP-hard problem. We propose several heuristic algorithms and simulate their performance under various traffic conditions and on various network topologies.