Establishing the Viability of End System Multicast using a Systems Approach to Protocol Design

摘要

This thesis is motivated by the vision of enabling ubiquitous deployment of applications such as audio/video conferencing and broadcasting over the Internet. For over 15 years, researchers have attempted to enable such applications using the IP Multicast architecture. However, concerns regarding per-group state in routers, deployment issues, and difficulties with supporting higher level functionality, such as reliability and congestion control, have prevented IP Multicast from taking root. The author contends that 'it is feasible to efficiently enable group communication applications on the Internet without router and IP level support.' He demonstrates this in the context of an alternate architecture that he calls 'End System Multicast.' Here, end systems implement all multicast functionality, including membership management and packet replication. By eliminating state in routers, and exploiting application- specific intelligence, he argues that End System Multicast can address the fundamental concerns with IP Multicast. He presents the design and implementation of protocols for constructing efficient overlays among participating end systems in a self-organizing manner. The scale of nodes involved and the dynamic and heterogeneous nature of the Internet make the design of these protocols different than traditional distributed algorithms. He presents Narada, the first published self-organizing protocol for overlay multicast. He also presents Sparta, a protocol deployed in a fully operational broadcasting system based on End System Multicast. The system has been used to broadcast several events, and has been used by thousands of users. The thesis adopts an integrated approach to validating architecture, protocol design, and systems building. The protocols address issues such as constructing bandwidth- optimized overlays and node heterogeneity that are critical in building operational systems, yet overlooked by the community.