RFC 3425 (rfc3425) - Page 2 of 5
Obsoleting IQUERY
Alternative Format: Original Text Document
RFC 3425 Obsoleting IQUERY November 2002
Response packets from these megaservers could be exceptionally large,
and easily run into megabyte sizes. For example, using IQUERY to
find every domain that is delegated to one of the nameservers of a
large ISP could return tens of thousands of 3-tuples in the question
section. This could easily be used to launch denial of service
attacks.
Operators of servers that do support IQUERY in some form (such as
very old BIND 4 servers) generally opt to disable it. This is
largely due to bugs in insufficiently-exercised code, or concerns
about exposure of large blocks of names in their zones by probes such
as inverse MX queries.
IQUERY is also somewhat inherently crippled by being unable to tell a
requester where it needs to go to get the information that was
requested. The answer is very specific to the single server that was
queried. This is sometimes a handy diagnostic tool, but apparently
not enough so that server operators like to enable it, or request
implementation where it is lacking.
No known clients use IQUERY to provide any meaningful service. The
only common reverse mapping support on the Internet, mapping address
records to names, is provided through the use of pointer (PTR)
records in the in-addr.arpa tree and has served the community well
for many years.
Based on all of these factors, this document recommends that the
IQUERY operation for DNS servers be officially obsoleted.
2 - Requirements
The key word "SHOULD" in this document is to be interpreted as
described in BCP 14, RFC 2119, namely that there may exist valid
reasons to ignore a particular item, but the full implications must
be understood and carefully weighed before choosing a different
course.
3 - Effect on RFC 1035
The effect of this document is to change the definition of opcode 1
from that originally defined in section 4.1.1 of RFC 1035, and to
entirely supersede section 6.4 (including subsections) of RFC 1035.
The definition of opcode 1 is hereby changed to:
"1 an inverse query (IQUERY) (obsolete)"
Lawrence Standards Track