8. Transition Considerations

A host that complies with this document will send ONLY source-specific host reports for addresses in the SSM range. As stated above, a router that receives a non-source-specific (e.g., IGMPv1 or IGMPv2 or MLDv1 [RFC2710]) host report for a source-specific multicast destination address MUST ignore these reports. Failure to do so would violate the SSM service model promised to the sender: that a packet sent to (S,G) would only be delivered to hosts that specifically requested delivery of packets sent to G by S.

During a transition period, it would be possible to deliver SSM datagrams in a domain where the routers do not support SSM semantics by simply forwarding any packet destined to G to all hosts that have requested subscription of (S,G) for any S. However, this implementation risks unduly burdening the network infrastructure by delivering (S,G) datagrams to hosts that did not request them. Such an implementation for addresses in the SSM range is specifically not compliant with Section 5.2 of this document.