


Network Working Group                                         M. Andrews
Internet-Draft                                                       ISC
Intended status: BCP                                      March 25, 2010
Expires: September 26, 2010


                        Locally-served DNS Zones
                draft-ietf-dnsop-default-local-zones-10

Abstract

   Experience with the Domain Name System (DNS) has shown that there are
   a number of DNS zones all iterative resolvers and recursive
   nameservers should automatically serve, unless configured otherwise.
   RFC 4193 specifies that this should occur for D.F.IP6.ARPA.  This
   document extends the practice to cover the IN-ADDR.ARPA zones for RFC
   1918 address space and other well known zones with similar
   characteristics.

Status of this Memo

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Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal



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   Provisions Relating to IETF Documents
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   than English.































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Reserved Words . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Effects on sites using RFC 1918 addresses. . . . . . . . . . .  4
   3.  Changes to Iterative Resolver Behaviour. . . . . . . . . . . .  4
   4.  Lists Of Zones Covered . . . . . . . . . . . . . . . . . . . .  5
     4.1.  RFC1918 Zones  . . . . . . . . . . . . . . . . . . . . . .  5
     4.2.  RFC3330 and RFC5737 Zones  . . . . . . . . . . . . . . . .  6
     4.3.  Local IPv6 Unicast Addresses . . . . . . . . . . . . . . .  6
     4.4.  IPv6 Locally Assigned Local Addresses  . . . . . . . . . .  7
     4.5.  IPv6 Link Local Addresses  . . . . . . . . . . . . . . . .  7
     4.6.  IPv6 Example Prefix  . . . . . . . . . . . . . . . . . . .  7
   5.  Zones that are Out-Of-Scope  . . . . . . . . . . . . . . . . .  7
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     9.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Appendix A.  Change History [To Be Removed on Publication] . . . . 10
     A.1.  draft-ietf-dnsop-default-local-zones-10.txt  . . . . . . . 10
     A.2.  draft-ietf-dnsop-default-local-zones-09.txt  . . . . . . . 10
     A.3.  draft-ietf-dnsop-default-local-zones-08.txt  . . . . . . . 11
     A.4.  draft-ietf-dnsop-default-local-zones-07.txt  . . . . . . . 11
     A.5.  draft-ietf-dnsop-default-local-zones-06.txt  . . . . . . . 11
     A.6.  draft-ietf-dnsop-default-local-zones-05.txt  . . . . . . . 11
     A.7.  draft-ietf-dnsop-default-local-zones-04.txt  . . . . . . . 11
     A.8.  draft-ietf-dnsop-default-local-zones-03.txt  . . . . . . . 11
     A.9.  draft-ietf-dnsop-default-local-zones-02.txt  . . . . . . . 11
     A.10. draft-ietf-dnsop-default-local-zones-01.txt  . . . . . . . 11
     A.11. draft-ietf-dnsop-default-local-zones-00.txt  . . . . . . . 11
     A.12. draft-andrews-full-service-resolvers-03.txt  . . . . . . . 12
     A.13. draft-andrews-full-service-resolvers-02.txt  . . . . . . . 12
   Appendix B.  Proposed Status [To Be Removed on Publication]  . . . 12
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12















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1.  Introduction

   Experience with the Domain Name System (DNS, [RFC1034] and [RFC1035])
   has shown that there are a number of DNS zones that all iterative
   resolvers and recursive nameservers SHOULD automatically serve,
   unless intentionally configured otherwise.  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
   unique local IPv6 addresses defined in [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 it has therefore become
   necessary to deploy sacrificial name servers to protect the immediate
   parent name servers for these zones from excessive, unintentional,
   query load [AS112] [I-D.draft-ietf-dnsop-as112-ops]
   [I-D.draft-ietf-dnsop-as112-under-attack-help-help].  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 for these name spaces but drop the
   responses, put a significant load on the root servers (forward but no
   reverse zones configured).  They also cause operational load for the
   root server operators as they have to reply to enquiries about why
   the root servers are "attacking" these clients.  Changing the default
   configuration will address all these issues for the zones listed in
   Section 4.

   [RFC4193] 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 public
   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.

   This recommendation should also help DNS responsiveness for sites
   which are using [RFC1918] addresses but do not follow the last
   paragraph in Section 3 of [RFC1918].

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].




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2.  Effects on sites using RFC 1918 addresses.

   For most sites using [RFC1918] addresses, the changes here will have
   little or no detrimental effect.  If the site does not already have
   the reverse tree populated the only effect will be that the name
   error responses will be generated locally rather than remotely.

   For sites that do have the reverse tree populated, most will either
   have a local copy of the zones or will be forwarding the queries to
   servers which have local copies of the zone.  Therefore this
   recommendation will not be relevant.

   The most significant impact will be felt at sites that make use of
   delegations for [RFC1918] addresses and have populated these zones.
   These sites will need to override the default configuration expressed
   in this document to allow resolution to continue.  Typically, such
   sites will be fully disconnected from the Internet and have their own
   root servers for their own non-Internet DNS tree.


3.  Changes to Iterative Resolver Behaviour.

   Unless configured otherwise, an iterative resolver will now return
   authoritatively (aa=1) name errors (RCODE=3) for queries within the
   zones in Section 4, with the obvious exception of queries for the
   zone name itself where SOA, NS and "no data" responses will be
   returned as appropriate to the query type.  One common way to do this
   all at once is to serve empty (SOA and NS only) zones.

   An implementation of this recommendation MUST provide a mechanism to
   disable this new behaviour, and SHOULD allow this decision 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 the origin of the responses and thus any leakage to the public
   Internet servers.  This document recommends that the NS record
   defaults to the name of the zone and the SOA MNAME defaults to the
   name of the only NS RR's target.  The SOA RNAME should default to
   "nobody.invalid."  [RFC2606].  Implementations SHOULD provide a
   mechanism to set these values.  No address records need to be
   provided for the name server.

   Below is an example of a generic empty zone in master file format.
   It will produce a negative cache TTL of 3 hours.

   @ 10800 IN SOA @ nobody.invalid. 1 3600 1200 604800 10800
   @ 10800 IN NS @



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   The SOA RR is needed to support negative caching [RFC2308] of name
   error responses and to point clients to the primary master for DNS
   dynamic updates.

   SOA values of particular importance are the MNAME, the SOA RR's TTL
   and the negTTL value.  Both TTL values SHOULD match.  The rest of the
   SOA timer values MAY be chosen arbitrarily since they are not
   intended to control any zone transfer activity.

   The NS RR is needed as some UPDATE [RFC2136] clients use NS queries
   to discover the zone to be updated.  Having no address records for
   the name server is expected to abort UPDATE processing in the client.


4.  Lists Of Zones Covered

   The following subsections are intended to seed the IANA registry as
   requested in the IANA Considerations Section.  The zone name is the
   entity to be registered.

4.1.  RFC1918 Zones

   The following zones correspond to the IPv4 address space reserved in
   [RFC1918].

                         +----------------------+
                         | Zone                 |
                         +----------------------+
                         | 10.IN-ADDR.ARPA      |
                         | 16.172.IN-ADDR.ARPA  |
                         | 17.172.IN-ADDR.ARPA  |
                         | 18.172.IN-ADDR.ARPA  |
                         | 19.172.IN-ADDR.ARPA  |
                         | 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 |
                         +----------------------+




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4.2.  RFC3330 and RFC5737 Zones

   The following zones correspond to those address ranges from [RFC3330]
   and [RFC5737] that are not expected to appear as source or
   destination addresses on the public Internet and to not have a unique
   name to associate with.

   The recommendation to serve an empty zone 127.IN-ADDR.ARPA is not a
   attempt to discourage any practice to provide a PTR RR for
   1.0.0.127.IN-ADDR.ARPA locally.  In fact, a meaningful reverse
   mapping should exist, but the exact setup is out of the scope of this
   document.  Similar logic applies to the reverse mapping for ::1
   (Section 4.3).  The recommendations made here simply assume no other
   coverage for these domains exists.

         +------------------------------+------------------------+
         | Zone                         | Description            |
         +------------------------------+------------------------+
         | 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 1        |
         | 100.51.198.IN-ADDR.ARPA      | IPv4 TEST NET 2        |
         | 113.0.203.IN-ADDR.ARPA       | IPv4 TEST NET 3        |
         | 255.255.255.255.IN-ADDR.ARPA | IPv4 BROADCAST         |
         +------------------------------+------------------------+

4.3.  Local IPv6 Unicast Addresses

   The reverse mappings ([RFC3596], Section 2.5 IP6.ARPA Domain) for the
   IPv6 Unspecified (::) and Loopback (::1) addresses ([RFC4291],
   Sections 2.4, 2.5.2 and 2.5.3) are covered by these two zones:

               +-------------------------------------------+
               | Zone                                      |
               +-------------------------------------------+
               | 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.IP6.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.IP6.ARPA      |
               +-------------------------------------------+

   Note: Line breaks and a escapes '\' have been inserted above for
   readability and to adhere to line width constraints.  They are not
   parts of the zone names.






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4.4.  IPv6 Locally Assigned Local Addresses

   Section 4.4 of [RFC4193] already required special treatment of:

                             +--------------+
                             | Zone         |
                             +--------------+
                             | D.F.IP6.ARPA |
                             +--------------+

4.5.  IPv6 Link Local Addresses

   IPv6 Link-Local Addresses as of [RFC4291], Section 2.5.6 are covered
   by four distinct reverse DNS zones:

                            +----------------+
                            | Zone           |
                            +----------------+
                            | 8.E.F.IP6.ARPA |
                            | 9.E.F.IP6.ARPA |
                            | A.E.F.IP6.ARPA |
                            | B.E.F.IP6.ARPA |
                            +----------------+

4.6.  IPv6 Example Prefix

   IPv6 example prefix [RFC3849].

                       +--------------------------+
                       | Zone                     |
                       +--------------------------+
                       | 8.B.D.0.1.0.0.2.IP6.ARPA |
                       +--------------------------+

   Note: 8.B.D.0.1.0.0.2.IP6.ARPA is not being used as a example here.


5.  Zones that are Out-Of-Scope

   IPv6 site-local addresses (deprecated, see [RFC4291] Sections 2.4 and
   2.5.7), and IPv6 Non-Locally Assigned Local addresses ([RFC4193]) 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 the zones C.E.F.IP6.ARPA through
   F.E.F.IP6.ARPA may still need to be deployed in the short term if the
   traffic becomes excessive.



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   For IPv6 Non-Locally Assigned Local addresses (L = 0) [RFC4193],
   there has been no decision made about whether the Regional Internet
   Registries (RIRs) 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 in
   Section 4.4.  If they do, then registries will need to take steps to
   ensure that name servers are provided for these addresses.

   This document also ignores IP6.INT.  IP6.INT has been wound up with
   only legacy resolvers now generating reverse queries under IP6.INT
   [RFC4159].

   This document has also deliberately ignored names immediately under
   the root domain.  While there is a subset of queries to the root name
   servers which could be addressed using the techniques described here
   (e.g. .local, .workgroup and IPv4 addresses), there is also a vast
   amount of traffic that requires a different strategy (e.g. lookups
   for unqualified hostnames, IPv6 addresses).


6.  IANA Considerations

   This document requests that IANA establish a registry of zones which
   require this default behaviour.  The initial contents of this
   registry are defined in Section 4.  Implementors are encouraged to
   periodically check this registry and adjust their implementations to
   reflect changes therein.

   This registry can be amended through "IETF Review" as per [RFC5226].

   IANA should co-ordinate with the RIRs to ensure that, as DNSSEC is
   deployed in the reverse tree, delegations for these zones are made in
   the manner described in Section 7.


7.  Security Considerations

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

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




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   It is recommended that sites actively using these namespaces secure
   them using DNSSEC [RFC4035] by publishing and using DNSSEC trust
   anchors.  This will protect the clients from accidental import of
   unsigned responses from the Internet.


8.  Acknowledgements

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


9.  References

9.1.  Normative References

   [RFC1034]  Mockapetris, P., "DOMAIN NAMES - CONCEPTS AND FACILITIES",
              STD 13, RFC 1034, November 1987.

   [RFC1035]  Mockapetris, P., "DOMAIN NAMES - IMPLEMENTATION AND
              SPECIFICATION", STD 13, RFC 1035, November 1987.

   [RFC1918]  Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
              and E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, February 1996.

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

   [RFC2136]  Vixie, P., Thomson, A., Rekhter, Y., and J. Bound,
              "Dynamic Updates in the Domain Name System (DNS UPDATE)",
              RFC 2136, April 1997.

   [RFC2308]  Andrews, M., "Negative Caching of DNS Queries (DNS
              NCACHE)", RFC 2398, March 1998.

   [RFC2606]  Eastlake, D. and A. Panitz, "Reserved Top Level DNS
              Names", BCP 32, RFC 2606, June 1999.

   [RFC3596]  Thomson, S., Huitema, C., Ksinant, V., and M. Souissi,
              "DNS Extensions to Support IPv6", RFC 3596, October 2003.

   [RFC4035]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Protocol Modifications for the DNS Security
              Extensions", RFC 4035, March 2005.

   [RFC4159]  Huston, G., "Deprecation of "ip6.int"", BCP 109, RFC 4159,
              August 2005.



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

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              October 2008.

9.2.  Informative References

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

   [I-D.draft-ietf-dnsop-as112-ops]
              Abley, J. and W. Maton, "AS112 Nameserver Operations",
              draft-ietf-dnsop-as112-ops-01 (work in progress),
              November 2007.

   [I-D.draft-ietf-dnsop-as112-under-attack-help-help]
              Abley, J. and W. Maton, "I'm Being Attacked by
              PRISONER.IANA.ORG!",
              draft-ietf-dnsop-as112-under-attack-help-help-01 (work in
              progress), November 2007.

   [RFC3330]  "Special-Use IPv4 Addresses", RFC 3330, September 2002.

   [RFC3849]  Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix
              Reserved for Documentation", RFC 3849, July 2004.

   [RFC5737]  Arkko, J., Cotton, M., and L. Vergoda, "IPv4 Address
              Blocks Reserved for Documentation", RFC 5737,
              January 2010.


Appendix A.  Change History [To Be Removed on Publication]

A.1.  draft-ietf-dnsop-default-local-zones-10.txt

   added RFC 5737 zones

A.2.  draft-ietf-dnsop-default-local-zones-09.txt

   refresh awaiting writeup







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A.3.  draft-ietf-dnsop-default-local-zones-08.txt

   editorial, reference updates

A.4.  draft-ietf-dnsop-default-local-zones-07.txt

   none, expiry prevention

A.5.  draft-ietf-dnsop-default-local-zones-06.txt

   add IPv6 example prefix

A.6.  draft-ietf-dnsop-default-local-zones-05.txt

   none, expiry prevention

A.7.  draft-ietf-dnsop-default-local-zones-04.txt

   Centrally Assigned Local addresses -> Non-Locally Assigned Local
   address

A.8.  draft-ietf-dnsop-default-local-zones-03.txt

   expanded section 4 descriptions

   Added references [RFC2136], [RFC3596],
   [I-D.draft-ietf-dnsop-as112-ops] and
   [I-D.draft-ietf-dnsop-as112-under-attack-help-help].

   Revised language.

A.9.  draft-ietf-dnsop-default-local-zones-02.txt

   RNAME now "nobody.invalid."

   Revised language.

A.10.  draft-ietf-dnsop-default-local-zones-01.txt

   Revised impact description.

   Updated to reflect change in IP6.INT status.

A.11.  draft-ietf-dnsop-default-local-zones-00.txt

   Adopted by DNSOP.

   "Author's Note" re-titled "Zones that are Out-Of-Scope"



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   Add note that these zone are expected to seed the IANA registry.

   Title changed.

A.12.  draft-andrews-full-service-resolvers-03.txt

   Added "Proposed Status".

A.13.  draft-andrews-full-service-resolvers-02.txt

   Added 0.IN-ADDR.ARPA.


Appendix B.  Proposed Status [To Be Removed on Publication]

   This Internet-Draft is being submitted for eventual publication as an
   RFC with a proposed status of Best Current Practice.


Author's Address

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

   Email: marka@isc.org























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