Nits: 1. In Abstract, the abbreviation is missed when the Term are firstly appeared, such as: Sparse-Mode, Rendezvous Point; 2. Every word in the section titles should be in the capital form Issues: 1. In Security Considerations section, should one sentence be "even if the sources are actually not active"? 2. Generally, the peer authentication (by certificate, shared key...) and the message integration protection are always helpful to defend against the forged routers and PEM messages, even the resulted resource consumption. But in current Security Considerations section, there is nothing discussed about these countermeasures, even in the general way. Suggest to consider this point personally.