[dns-wg] use of "rev-srv" attribute in "inetnum" (and "inet6num") objects

Dear colleagues,

rather recently I was involved in clearing up some old inetnum assignments
in the RIPE database. During that archaeologic work a couple of objects with
the "rev-srv" attribute were discovered and it turned out that the presence of
this attribute not necessarily contributed to an easy solution.

The rev-srv attribute was intended to specify the name servers for the "reverse
mapping" for a given address range. However, it is just informative in nature.
For quite some time now the automatic generation of the IN-ADDR.ARPA zones has
been based solely on the "domain" objects (see <http://www.ripe.net/reverse/>).

So, it turns out "rev-srv" has some disadvantages:

(D1) the "rev-srv" attribute is redundant, because only "domain" objects
     cause delegations to be present in reverse zone maintained by the NCC
(D2) "rev-srv" lacks consistency checks with both the reality and any
     potential "domain" object; several attributes just contain incorrect
     information
(D3) the "rev-srv" attribute does not really help finding the zone for
     address ranges smaller than /24 (where delegations are following RFC 2317)

On the other hand, it might still have advantages:

(A1) where there is a delegation from an NCC maintained zone to an LIR for,
     say, a /16 address range, the "rev-srv" attribute for enclosed /24s
     may provide useful additional information
(A2) even if the leaf zone name cannot be guessed for RFC 2317 delegations,
     the "rev-srv" attribute might help in locating the zone containing the
     CNAME RRs
(A3) "rev-srv" attributes could provide additional information in legacy
     class B space

(D1), (D2), and (A1) similarly apply to v6 reverse and inet6num objects.

Today, approximately 5% of all "inetnum" objects have at least one "rev-srv"
attribute. Of these objects, 17% have been changed in 2007 (which does
not imply the rev-srv was changed or checked), and 35% were changed in 2006
or 2007.  That means "rev-srv" does not only appear in old objects, but may
still be carried as a legacy.  The objects with "rev-srv" are maintained by
1300 different maintainers, almost 500 of which own only a single object
with "rev-srv".

Given the confusion mentioned in the introduction and looking at the pros and
cons (where the lists above are not meant to be exhaustive), what is the use of
"rev-srv" for a "user" of the object or for its publisher/maintainer?

The DB WG chairs' advice was that the purpose and/or future of "rev-srv"
should be discussed here first.  That said, what do you think about
deprecating the "rev-srv" attribute?

-Peter (speaking as $self)