The bottom line is that RFC 1464 was a syntax proposal design
to simplify
information sharing. A registry was proposed to control name
collisions, but
that never happened. It still seems to be a reasonable
approach and perhaps
someone will put it back on the standards track someday if
appropriate.
I agree with most of the idea, but I don't agree with the
registry part.
According to ICANN, IANA is costing $700,000 a year to
maintain. I think it is time to either look at why it
costs so much and work to reduce it, or start looking for
engineering designs that do not depend on registry functions.
In the case of DNS RR prefixing there is no real problem
since the possible name space is essentially unlimited.
The chance of accidental collision is minimal.
The value that a registry would provide is as a concordance.
The engineering way to deal with this problem would be to move
to a competent document format such as XML, assign all
code points automatically from a dictionary and build the
concodances and indexes automatically from the documents
themselves.
This is somewhat over-engineered for our case since we
already have a unique key, the group name is in theory
unique over time.
Using _MARID as the prefix is practically guaranteed to
be accidental collision free.
Adding the protocol identifier to the base prefix is
arguably an improvement, since we might use _SMPT._MARID.