There was a long discussion about this issue on the roll(_at_)ietf(_dot_)org
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(_at_)ietf(_dot_)org 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