Dave has been talking about this in various forums for about 6 to 8 months.
What are the current issues? What are some of the near-term futures? What do ISPs need?
There is little or no work that has been done on IDR issues in multicast.
RPF check builds a spanning tree and is fully distributed. It can be used to implement policy. It's like a packet filter in that it does a number of functions for each packet.
The data is broadcast throughout the Internet until someone says to stop. This is a source based distribution tree. There are many more state requirements than those in sparse mode. Source trees are fully distributed and optimal reverse paths with low delay. Does it scale well? Probably not.
In a sparse mode, an explicit join mechanism is employed. Explicit joins build a shared distribution tree.
The state requirement is probably less and is it not state driven. However, this mode is suboptimal for
Interprovider connectivities.
Unicast routing is overloaded since it is used for both unicast and multicast, but the mechanism is not the same.
A Third provider resource dependency is possible.
The Distance Core/RP problem results when neither source/destination has an RP.
What we need is:
Dave plans build a document with input from folks.
Note:Dave's comments look liks this.
Bill asks: Most people are doing multicast tunnels. Why Is that? Chicken & Egg. Medium and Tier1 providers are not seeing much demand for multicast. Some protocols may be too complex to be implemented in small routers.