IP multicasting for point-to-point local distribution

While support for IP multicasting continues to spread enabling new applications, an increasing number of hosts connects to the worldwide Internet via low bandwidth point-to-point links, such as wireline or wireless telephone lines. We discuss existing proposals for local and wide area IP multicasting and their implications for point-to-point links, identify problems with their integration in this environment, and propose alternative special purpose mechanisms to solve these problems. The main problems are overhead due to IGMP leave latency and unnecessary continuous probing of potentially power constrained hosts. Our solution is an alternative to IGMP mechanisms based on join/leave messages for tracking group membership over PtP networks. After presenting the implementation requirements of the proposed and existing mechanisms, we compare them with respect to the performance, interoperability, robustness and implementation complexity, demonstrating that our join/leave protocol is uniformly superior.