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Network Working Group                                         M. Andrews
Internet-Draft                                                       ISC
Expires: August 27, 2006                               February 23, 2006


 Configuration Issues Facing Full Service DNS Resolvers In The Presence
                     of Private Network Addressing
                draft-andrews-full-service-resolvers-02

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   Practice has shown that there are a number of zones all full service
   resolvers should, unless configured otherwise, automatically serve.
   RFC4193 already specifies that this should occur for D.F.IP6.ARPA.
   This document extends the practice to cover the IN-ADDR.ARPA zones
   for RFC1918 address space and other well known zones with similar
   usage constraints.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Reserved Words  . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Effects on sites using RFC1918 addresses. . . . . . . . . . . . 3
   3.  Changes To Full Service Resolver Behaviour. . . . . . . . . . . 4
   4.  Lists Of Zones Covered  . . . . . . . . . . . . . . . . . . . . 4
     4.1.  RFC1918 Zones . . . . . . . . . . . . . . . . . . . . . . . 4
     4.2.  RFC3330 Zones . . . . . . . . . . . . . . . . . . . . . . . 5
     4.3.  Local IPv6 Unicast Addresses  . . . . . . . . . . . . . . . 5
     4.4.  IPv6 Locally Assigned Local Addresses . . . . . . . . . . . 5
     4.5.  IPv6 Link Local Addresses . . . . . . . . . . . . . . . . . 5
   5.  Author's Note . . . . . . . . . . . . . . . . . . . . . . . . . 5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   9.  Change History  . . . . . . . . . . . . . . . . . . . . . . . . 7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     10.1. Normative References  . . . . . . . . . . . . . . . . . . . 7
     10.2. Informative References  . . . . . . . . . . . . . . . . . . 7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 8
   Intellectual Property and Copyright Statements  . . . . . . . . . . 9





























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1.  Introduction

   Practice has shown that there are a number of zones all full service
   resolvers should, unless configured otherwise, automatically serve.
   These zones include, but are not limited to, the IN-ADDR.ARPA zones
   for the address space allocated by [RFC1918] and the IP6.ARPA zones
   for locally assigned local IPv6 addresses, [RFC4193].

   This recommendation is made because data has shown that significant
   leakage of queries for these name spaces is occurring, despite
   instructions to restrict them, and because sacrificial name servers
   have been deployed to protect the immediate parent name servers for
   these zones from excessive, unintentional, query load [AS112].  There
   is every expectation that the query load will continue to increase
   unless steps are taken as outlined here.

   Additionally, queries from clients behind badly configured firewalls
   that allow outgoing queries but drop responses for these name spaces
   also puts a significant load on the root servers.  They also cause
   operational load for the root server operators as they have to reply
   to queries about why the root servers are "attacking" these clients.
   Changing the default configuration will address all these issues for
   the zones below.

   [RFC4193] already recommends that queries for D.F.IP6.ARPA be handled
   locally.  This document extends the recommendation to cover the IN-
   ADDR.ARPA zones for [RFC1918] and other well known IN-ADDR.ARPA and
   IP6.ARPA zones for which queries should not appear on the Internet.

   It is hoped that by doing this the number of sacrificial servers
   [AS112] will not have to be increased and may in time be reduced.

   It should also help DNS responsiveness for sites which are using
   [RFC1918] addresses but are misconfigured.

1.1.  Reserved Words

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].


2.  Effects on sites using RFC1918 addresses.

   Sites using [RFC1918] addresses should already be serving these
   queries internally, without referring them to public name servers on
   the Internet.




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   The main impact will be felt on sites that make use of recursion for
   reverse lookups for [RFC1918] addresses and have populated these
   zones.  Typically, such sites will be fully disconnected from the
   Internet and have their own root servers for their own non-Internet
   DNS tree or make use of local delegation overrides (otherwise known
   as "forwarding") to reach the private servers for these reverse
   zones.  These sites will need to override the default configuration
   proposed in this draft to allow resolution to continue.

   Other sites that use [RFC1918] addresses and either have local copies
   of the reverse zones or don't have reverse zones configured should
   see no difference other than the name error appearing to come from a
   different source.


3.  Changes To Full Service Resolver Behaviour.

   Unless configured otherwise, a full service resolver will return name
   errors for queries within the lists of zones covered below.  One
   common way to do this is to serve empty (SOA and NS only) zones.

   A server doing this MUST provide a mechanism to disable this
   behaviour, preferably on a zone by zone basis.

   If using empty zones one should not use the same NS and SOA records
   as used on the public Internet servers as that will make it harder to
   detect leakage from the public Internet servers.  This document
   recommends that the NS record default to the name of the zone and the
   SOA MNAME default to the name of the zone.  The SOA RNAME should
   default to ".".  Implementations SHOULD provide a mechanism to set
   these values.  No address records need to be provided for the name
   server.

   @ 10800 IN SOA @ . 1 3600 1200 604800 10800
   @ 10800 IN NS @


4.  Lists Of Zones Covered

4.1.  RFC1918 Zones

      10.IN-ADDR.ARPA
      16.172.IN-ADDR.ARPA
      17.172.IN-ADDR.ARPA
      18.172.IN-ADDR.ARPA
      19.172.IN-ADDR.ARPA





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      20.172.IN-ADDR.ARPA
      21.172.IN-ADDR.ARPA
      22.172.IN-ADDR.ARPA
      23.172.IN-ADDR.ARPA
      24.172.IN-ADDR.ARPA
      25.172.IN-ADDR.ARPA
      26.172.IN-ADDR.ARPA
      27.172.IN-ADDR.ARPA
      28.172.IN-ADDR.ARPA
      29.172.IN-ADDR.ARPA
      30.172.IN-ADDR.ARPA
      31.172.IN-ADDR.ARPA
      168.192.IN-ADDR.ARPA

4.2.  RFC3330 Zones

      0.IN-ADDR.ARPA /* IPv4 "THIS" NETWORK */
      127.IN-ADDR.ARPA /* IPv4 LOOP-BACK NETWORK */
      254.169.IN-ADDR.ARPA /* IPv4 LINK LOCAL */
      2.0.192.IN-ADDR.ARPA /* IPv4 TEST NET */
      255.255.255.255.IN-ADDR.ARPA /* IPv4 BROADCAST */

4.3.  Local IPv6 Unicast Addresses

      0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP
      6.ARPA
      1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP
      6.ARPA

4.4.  IPv6 Locally Assigned Local Addresses

      D.F.IP6.ARPA

4.5.  IPv6 Link Local Addresses

      8.E.F.IP6.ARPA
      9.E.F.IP6.ARPA
      A.E.F.IP6.ARPA
      B.E.F.IP6.ARPA


5.  Author's Note

   IPv6 site-local addresses and IPv6 Globally Assigned Local addresses
   are not covered here.  It is expected that IPv6 site-local addresses
   will be self correcting as IPv6 implementations remove support for
   site-local addresses however, sacrificial servers for C.E.F.IP6.ARPA
   to F.E.F.IP6.ARPA may still need to be deployed in the short term if



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   the traffic becomes excessive.

   For IPv6 Globally Assigned Local addresses there has been no decision
   made about whether the registries will provide delegations in this
   space or not.  If they don't then C.F.IP6.ARPA will need to be added
   to the list above.  If they do then registries will need to take
   steps to ensure that name servers are provided for these addresses.

   This document is also ignoring the IP6.INT counterpart for the
   IP6.ARPA addresses above.  IP6.INT is in the process of being wound
   up with clients already not querying for this suffix.

   This document has also deliberately ignored zones immediately under
   the root.  The author believes other methods would be more applicable
   for dealing with the excess / bogus traffic these generate.


6.  IANA Considerations

   This document recommends that IANA establish a registry of zones
   which require this default behaviour, the initial contents are above.
   More zones are expected to be added, and possibly deleted from this
   registry over time.  Name server implementors are encouraged to check
   this registry and adjust their implementations to reflect changes
   therein.

   This registry can be amended through IESG reviewed RFC publication.


7.  Security Considerations

   During the initial deployment phase, particularly where [RFC1918]
   addresses are in use, there may be some clients that unexpectedly
   receive name error rather than a PTR record.  This may cause some
   service disruption until full service resolvers have been re-
   configured.

   When DNSSEC is deployed within the IN-ADDR.ARPA and IP6.ARPA
   namespaces, the zones listed above will need to be delegated as
   insecure delegations.  This will allow DNSSEC validation to succeed
   for queries in these spaces despite not being answered from the
   delegated servers.

   It is recommended that sites actively using these namespaces secure
   them using DNSSEC.  This is good just on general principles.  It will
   also protect the clients from accidental leakage of answers from the
   Internet which will be unsigned.




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8.  Acknowledgements

   This work was supported by the US National Science Foundation
   (research grant SCI-0427144) and DNS-OARC.


9.  Change History

   Changes from draft-andrews-full-service-resolvers-01.txt.  Added
   0.IN-ADDR.ARPA.


10.  References

10.1.  Normative References

   [RFC1918]  Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
              and E. Lear, "Address Allocation for Private Internets",
              RFC 1918, February 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

10.2.  Informative References

   [AS112]    "AS112 Project", <http://as112.net/>.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005.






















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Author's Address

   Mark P. Andrews
   Internet Systems Consortium
   950 Charter Street
   Redwood City, CA  94063
   US

   Email: Mark_Andrews@isc.org










































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