Multicast Lessons Learned from Decades of Deployment Experience

This document gives a historical perspective about the design and deployment of multicast routing protocols. The document describes the technical challenges discovered from building these protocols. Even though multicast has enjoyed success of deployment in special use-cases, this draft discusses what were, and are, the obstacles for mass deployment across the Internet. Individuals who are working on new multicast related protocols will benefit by knowing why certain older protocols are no longer in use today.