Network Working Group M. Andrews
Internet-Draft ISC
Intended status: Best Current March 2, 2007
Practice
Expires: September 3, 2007
Locally-served DNS Zones
draft-ietf-dnsop-default-local-zones-01
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Copyright (C) The IETF Trust (2007).
Abstract
Practice has shown that there are a number of DNS zones all iterative
resolvers and recursive nameservers should, unless configured
otherwise, automatically serve. RFC 4193 already 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 usage constraints.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Reserved Words . . . . . . . . . . . . . . . . . . . . . . 3
2. Effects on sites using RFC 1918 addresses. . . . . . . . . . . 3
3. Changes to Iterative Resolver Behaviour. . . . . . . . . . . . 4
4. Lists Of Zones Covered . . . . . . . . . . . . . . . . . . . . 5
4.1. RFC 1918 Zones . . . . . . . . . . . . . . . . . . . . . . 5
4.2. RFC 3330 Zones . . . . . . . . . . . . . . . . . . . . . . 5
4.3. Local IPv6 Unicast Addresses . . . . . . . . . . . . . . . 6
4.4. IPv6 Locally Assigned Local Addresses . . . . . . . . . . 6
4.5. IPv6 Link Local Addresses . . . . . . . . . . . . . . . . 6
5. Zones that are Out-Of-Scope . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . . 8
Appendix A. Change History [To Be Removed on Publication] . . . . 9
A.1. draft-ietf-dnsop-default-local-zones-01.txt . . . . . . . 9
A.2. draft-ietf-dnsop-default-local-zones-00.txt . . . . . . . 9
A.3. draft-andrews-full-service-resolvers-03.txt . . . . . . . 9
A.4. draft-andrews-full-service-resolvers-02.txt . . . . . . . 9
Appendix B. Proposed Status [To Be Removed on Publication] . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9
Intellectual Property and Copyright Statements . . . . . . . . . . 10
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1. Introduction
Practice has shown that there are a number of DNS [RFC 1034] [RFC
1035] zones all iterative resolvers and recursive nameservers 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 [RFC 1918] and the IP6.ARPA zones for
locally assigned local IPv6 addresses, [RFC 4193].
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 listed below in Section 4.
[RFC 4193] 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 [RFC 1918] 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.
It should also help DNS responsiveness for sites which are using [RFC
1918] addresses but do not follow the last paragraph in section 3 of
[RFC 1918].
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 [RFC 2119].
2. Effects on sites using RFC 1918 addresses.
For most sites using [RFC 1918] addresses, the changes here will have
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little or no detrimental effect. If the site does not already have
the reverse tree populated the only effect will be that the answers
are 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. In either case the
local resolver has a pre-existing configuration for the namespace and
won't add the automatic zone.
The main impact will be felt at sites that make use of delegation for
reverse lookups for [RFC 1918] 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. These sites will need to override the default
configuration expressed in this document to allow resolution to
continue.
3. Changes to Iterative Resolver Behaviour.
Unless configured otherwise, an iterative resolver will now return
name errors (RCODE=3) for queries within the lists of zones covered
below, 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 is to serve empty (SOA
and NS only) zones.
A implementation doing this MUST provide a mechanism to disable this
new 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 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 ".". Implementations SHOULD provide a
mechanism to set these values. No address records need to be
provided for the name server.
Below is a example of a generic empty zone in master file format. It
will produce a negative cache ttl of 3 hours.
@ 10800 IN SOA @ . 1 3600 1200 604800 10800
@ 10800 IN NS @
The SOA RR is needed to support negative caching [RFC 2308] of name
error responses and to point clients to the primary master for DNS
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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 it they are not
intended to control any zone transfer activity.
The NS RR is needed as some UPDATE clients use NS queries to discover
they zone to be updated. Having no address records for the name
server should abort UPDATE processing in the client
4. Lists Of Zones Covered
The lists below are expected to seed a IANA registry.
4.1. RFC 1918 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
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. RFC 3330 Zones
See [RFC 3330].
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 */
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4.3. Local IPv6 Unicast Addresses
See [RFC 4291], sections 2.4, 2.5.2 and 2.5.3.
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
See [RFC 4193].
D.F.IP6.ARPA
4.5. IPv6 Link Local Addresses
See [RFC 4291], sections 2.4 and 2.5.6.
8.E.F.IP6.ARPA
9.E.F.IP6.ARPA
A.E.F.IP6.ARPA
B.E.F.IP6.ARPA
5. Zones that are Out-Of-Scope
IPv6 site-local addresses, [RFC 4291] sections 2.4 and 2.57, and IPv6
Globally Assigned Local [RFC 4193] 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 the traffic becomes
excessive.
For IPv6 Globally Assigned Local addresses [RFC 4291] 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 IP6.INT. IP6.INT has been wound up
with only legacy resolvers now generating reverse queries under
IP6.INT.
This document has also deliberately ignored names immediately under
the root. While there is a subset of queries to the roots which
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could be addressed using the techniques described here (e.g. .local
and IPv4 addresses) there is also a vast amount of traffic that
requires a different strategy (e.g. lookups for unqualied hostnames,
IPv6 addresses).
6. IANA Considerations
This document recommends that IANA establish a registry of zones
which require this default behaviour, the initial contents of which
are in Section 4. 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 "IETF Consensus" as per [RFC
2434] or IETF Review in 2434bis.
IANA should co-ordinate with the RIRs and ICANN to ensure the DNSSEC
deployment in the reverse trees that these zone are delegated in a
unsecure manner as per Security Considerations.
7. Security Considerations
During the initial deployment phase, particularly where [RFC 1918]
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 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 [RFC 4035] by publishing and using DNSSEC trust
anchors. This will protect the clients from accidental leakage of
unsigned answers from the Internet.
8. Acknowledgements
This work was supported by the US National Science Foundation
(research grant SCI-0427144) and DNS-OARC.
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9. References
9.1. Normative References
[RFC 1034]
Mockapetris, P., "DOMAIN NAMES - CONCEPTS AND FACILITIES",
RFC 1034, STD 13, November 1987.
[RFC 1035]
Mockapetris, P., "DOMAIN NAMES - IMPLEMENTATION AND
SPECIFICATION", RFC 1035, STD 13, November 1987.
[RFC 1918]
Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
and E. Lear, "Address Allocation for Private Internets",
RFC 1918, February 1996.
[RFC 2119]
Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 2308]
Andrews, M., "Negative Caching of DNS Queries (DNS
NCACHE)", RFC 2398, March 1998.
[RFC 2434]
Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[RFC 3330]
"Special-Use IPv4 Addresses", RFC 3330, September 2002.
[RFC 4035]
Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, March 2005.
[RFC 4291]
Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
9.2. Informative References
[AS112] "AS112 Project", <http://as112.net/>.
[RFC 4193]
Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
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Addresses", RFC 4193, October 2005.
Appendix A. Change History [To Be Removed on Publication]
A.1. draft-ietf-dnsop-default-local-zones-01.txt
Revised impact description.
Updated to reflect change in IP6.INT status.
A.2. draft-ietf-dnsop-default-local-zones-00.txt
Adopted by DNSOP.
"Author's Note" re-titled "Zones that are Out-Of-Scope"
Add note that these zone are expected to seed the IANA registry.
Title changed.
A.3. draft-andrews-full-service-resolvers-03.txt
Added "Proposed Status".
A.4. 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: Mark_Andrews@isc.org
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