GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc3197

Network Working Group R. Austein Request for Comments: 3197 InterNetShare Category: Informational November 2001

           Applicability Statement for DNS MIB Extensions

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

 This document explains why, after more than six years as proposed
 standards, the DNS Server and Resolver MIB extensions were never
 deployed, and recommends retiring these MIB extensions by moving them
 to Historical status.

1. History

 The road to the DNS MIB extensions was paved with good intentions.
 In retrospect, it's obvious that the working group never had much
 agreement on what belonged in the MIB extensions, just that we should
 have some.  This happened during the height of the craze for MIB
 extensions in virtually every protocol that the IETF was working on
 at the time, so the question of why we were doing this in the first
 place never got a lot of scrutiny.  Very late in the development
 cycle we discovered that much of the support for writing the MIB
 extensions in the first place had come from people who wanted to use
 SNMP SET operations to update DNS zones on the fly.  Examination of
 the security model involved, however, led us to conclude that this
 was not a good way to do dynamic update and that a separate DNS
 Dynamic Update protocol would be necessary.
 The MIB extensions started out being fairly specific to one
 particular DNS implementation (BIND-4.8.3); as work progressed, the
 BIND-specific portions were rewritten to be as implementation-neutral
 as we knew how to make them, but somehow every revision of the MIB
 extensions managed to create new counters that just happened to
 closely match statistics kept by some version of BIND.  As a result,
 the MIB extensions ended up being much too big, which raised a number

Austein Informational [Page 1] RFC 3197 Applicability Statement - DNS MIB Extensions November 2001

 of concerns with the network management directorate, but the WG
 resisted every attempt to remove any of these variables.  In the end,
 large portions of the MIB extensions were moved into optional groups
 in an attempt to get the required subset down to a manageable size.
 The DNS Server and Resolver MIB extensions were one of the first
 attempts to write MIB extensions for a protocol usually considered to
 be at the application layer.  Fairly early on it became clear that,
 while it was certainly possible to write MIB extensions for DNS, the
 SMI was not really designed with this sort of thing in mind.  A case
 in point was the attempt to provide direct indexing into the caches
 in the resolver MIB extensions: while arguably the only sane way to
 do this for a large cache, this required much more complex indexing
 clauses than is usual, and ended up running into known length limits
 for object identifiers in some SNMP implementations.
 Furthermore, the lack of either real proxy MIB support in SNMP
 managers or a standard subagent protocol meant that there was no
 reasonable way to implement the MIB extensions in the dominant
 implementation (BIND).  When the AgentX subagent protocol was
 developed a few years later, we initially hoped that this would
 finally clear the way for an implementation of the DNS MIB
 extensions, but by the time AgentX was a viable protocol it had
 become clear that nobody really wanted to implement these MIB
 extensions.
 Finally, the MIB extensions took much too long to produce.  In
 retrospect, this should have been a clear warning sign, particularly
 when the WG had clearly become so tired of the project that the
 authors found it impossible to elicit any comments whatsoever on the
 documents.

2. Lessons

 Observations based on the preceding list of mistakes, for the benefit
 of anyone else who ever attempts to write DNS MIB extensions again:
  1. Define a clear set of goals before writing any MIB extensions.

Know who the constituency is and make sure that what you write

    solves their problem.
  1. Keep the MIB extensions short, and don't add variables just

because somebody in the WG thinks they'd be a cool thing to

    measure.
  1. If some portion of the task seems to be very hard to do within the

SMI, that's a strong hint that SNMP is not the right tool for

    whatever it is that you're trying to do.

Austein Informational [Page 2] RFC 3197 Applicability Statement - DNS MIB Extensions November 2001

  1. If the entire project is taking too long, perhaps that's a hint

too.

3. Recommendation

 In view of the community's apparent total lack of interest in
 deploying these MIB extensions, we recommend that RFCs 1611 and 1612
 be reclassified as Historical documents.

4. Security Considerations

 Re-classifying an existing MIB document from Proposed Standard to
 Historic should not have any negative impact on security for the
 Internet.

5. IANA Considerations

 Getting rid of the DNS MIB extensions should not impose any new work
 on IANA.

6. Acknowledgments

 The author would like to thank all the people who were involved in
 this project over the years for their optimism and patience,
 misguided though it may have been.

7. References

 [DNS-SERVER-MIB]     Austein, R. and J. Saperia, "DNS Server MIB
                      Extensions", RFC 1611, May 1994.
 [DNS-RESOLVER-MIB]   Austein, R. and J. Saperia, "DNS Resolver MIB
                      Extensions", RFC 1612, May 1994.
 [DNS-DYNAMIC-UPDATE] Vixie, P., Thomson, S., Rekhter, Y. and J.
                      Bound, "Dynamic Updates in the Domain Name
                      System (DNS UPDATE)", RFC 2136, April 1997.
 [AGENTX]             Daniele, M., Wijnen, B., Ellison, M., and D.
                      Francisco, "Agent Extensibility (AgentX)
                      Protocol Version 1", RFC 2741, January 2000.

Austein Informational [Page 3] RFC 3197 Applicability Statement - DNS MIB Extensions November 2001

8. Author's Address

 Rob Austein
 InterNetShare, Incorporated
 325M Sharon Park Drive, Suite 308
 Menlo Park, CA  94025
 USA
 EMail: sra@hactrn.net

Austein Informational [Page 4] RFC 3197 Applicability Statement - DNS MIB Extensions November 2001

9. Full Copyright Statement

 Copyright (C) The Internet Society (2001).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Austein Informational [Page 5]

/data/webs/external/dokuwiki/data/pages/rfc/rfc3197.txt · Last modified: 2001/11/26 19:51 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki