Matthias Wählisch, Thomas C. Schmidt,
Between Underlay and Overlay: On Deployable Efficient Mobility-agnostic Group Communication Services,
Internet Research, Vol. 17, No. 5, pp. 519--534, Bingley, UK:Emerald Insight, November 2007.
Abstract: Multicast communication services are one of the longest debated issues in the 30 years history of the Internet. Disagreement over innumerous approaches and solutions to the IP host group model has led to a strongly divergent state of deployment. Stimulated by the need of applications alternative multicast mechanisms have been developed. P2P technologies have enabled group distribution on the application or service middleware layer. A significantly sim¬plified routing approach gave rise to the lean, source-specific multicast in IP. Henceforth the debate developed about which approach proves suitable for providing the superior capabilities towards a scalable, efficient and deployable group communication service. This paper discusses problems, requirements and current trends for deploying group communication in real-world scenarios from an integrated perspective. We introduce Hybrid Shared Tree, a new architecture and routing approach to combine network- and subnetwork-layer multicast services in end-system domains with transparent, structured overlays on the inter-domain level. This hybrid solution is highly scalable and robust and offers provider-oriented features to stimulate deployment. Furthermore, a straight forward perspective is indicated for a mobility-agnostic routing layer for future use.