There was a long discussion about this issue on the roll@xxxxxxxx mailing list: draft-ietf-roll-trickle-mcast-05 and draft-ietf-6man-multicast-scopes-00 are in conflict with each other. >From draft-ietf-roll-trickle-mcast-05: When used with MPL, Realm-Local scope is administratively defined and used to define the boundaries of multicast message dissemination by MPL. >From draft-ietf-6man-multicast-scopes-00: Realm-Local scope is the largest scope that is automatically configured, i.e., automatically derived from physical connectivity or other, non-multicast-related configuration. Specifically, "administratively defined" seems to me to be in direct conflict with "automatically configured". I think I've read consensus in the various discussion threads to make the following change to draft-ietf-roll-trickle-mcast-05: OLD: When used with MPL, Realm-Local scope is administratively defined and used to define the boundaries of multicast message dissemination by MPL. NEW: When used with MPL, Realm-Local scope is defined according to the underlying network technology; for example, [cite the IP-over-IEEE802.15.4 definition]. where "the IP-over-IEEE802.15.4 definition" is text to be published elsewhere (perhaps draft-ietf-6man-multicast-scopes) that defines scop 3 for IEEE802.15.4 mesh networks. I read less strong consensus (less discussion) of the following proposed changes: NEW (to be added immediately following text describing the use of Realm-Local scope): Admin-Local scope (scop value 4) can also be used with MPL in deployments that use administratively defined scopes that cover, for example, multiple subnets based on different underlying network technologies. As a side note, there is a related discussion about draft-ietf-6man-multicast-scopes on the 6man@xxxxxxxx mailing list. The term "Realm-Local scope" may change (should be changed for consistency with) the final published version of draft-ietf-6man-multicast-scopes. - Ralph