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Versions: (draft-jabley-dnsop-as112-dname) 00 01 02 03 04 05 06 RFC 7535

Network Working Group                                           J. Abley
Internet-Draft                                                 Dyn, Inc.
Updates: 6304 (if approved)                                   B. Dickson
Intended status: Informational                             Verisign Labs
Expires: August 18, 2014                                       W. Kumari
                                                           G. Michaelson
                                                       February 14, 2014

                     AS112 Redirection using DNAME


   Many sites connected to the Internet make use of IPv4 addresses that
   are not globally unique.  Examples are the addresses designated in
   RFC 1918 for private use within individual sites.

   Devices in such environments may occasionally originate Domain Name
   System (DNS) queries (so-called "reverse lookups") corresponding to
   those private-use addresses.  Since the addresses concerned have only
   local significance, it is good practice for site administrators to
   ensure that such queries are answered locally.  However, it is not
   uncommon for such queries to follow the normal delegation path in the
   public DNS instead of being answered within the site.

   It is not possible for public DNS servers to give useful answers to
   such queries.  In addition, due to the wide deployment of private-use
   addresses and the continuing growth of the Internet, the volume of
   such queries is large and growing.  The AS112 project aims to provide
   a distributed sink for such queries in order to reduce the load on
   the IN-ADDR.ARPA authoritative servers.  The AS112 project is named
   after the Autonomous System Number (ASN) that was assigned to it.

   The AS112 project does not accommodate the addition and removal of
   DNS zones elegantly.  Since additional zones of definitively local
   significance are known to exist, this presents a problem.  This
   document describes modifications to the deployment and use of AS112
   infrastructure that will allow zones to be added and dropped much
   more easily.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Design Overview  . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  AS112 Operations . . . . . . . . . . . . . . . . . . . . . . .  6
     3.1.  Extensions to Support DNAME Redirection  . . . . . . . . .  6
     3.2.  Redirection of Query Traffic to AS112 Servers  . . . . . .  6
   4.  Continuity of AS112 Operations . . . . . . . . . . . . . . . .  8
   5.  Candidate Zones for AS112 Redirection  . . . . . . . . . . . .  9
   6.  DNAME Deployment Considerations  . . . . . . . . . . . . . . . 10
   7.  IAB Considerations . . . . . . . . . . . . . . . . . . . . . . 11
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
     8.1.  Address Assignment . . . . . . . . . . . . . . . . . . . . 12
     8.2.  Hosting of AS112.ARPA  . . . . . . . . . . . . . . . . . . 12
     8.3.  Delegation of AS112.ARPA . . . . . . . . . . . . . . . . . 13
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 16
     11.2. Informative References . . . . . . . . . . . . . . . . . . 16
   Appendix A.  Assessing Support for DNAME in the Real World . . . . 17
     A.1.  Methodology  . . . . . . . . . . . . . . . . . . . . . . . 17
     A.2.  Results  . . . . . . . . . . . . . . . . . . . . . . . . . 19
   Appendix B.  Editorial Notes . . . . . . . . . . . . . . . . . . . 20
     B.1.  Change History . . . . . . . . . . . . . . . . . . . . . . 20
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21

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1.  Introduction

   The AS112 project is described in detail in [RFC6304].

   The AS112 nameservers (PRISONER.IANA.ORG, BLACKHOLE-1.IANA.ORG and
   BLACKHOLE-2.IANA.ORG) are required to answer authoritatively for each
   and every zone that is delegated to them.

   If a zone is delegated to AS112 nameservers without those nameservers
   being configured ahead of time to answer authoritatively for that
   zone, there is a detrimental impact on clients following referrals
   for queries within that zone.  This misconfiguration is colloquially
   known as a "lame delegation".

   AS112 nameserver operators are only loosely-coordinated, and hence
   adding support for a new zone (or, correspondingly, removing support
   for a zone that is no longer delegated to the AS112 nameservers) is
   difficult to accomplish with accuracy; testing AS112 nameservers
   remotely to see whether they are configured to answer authoritatively
   for a particular zone is similarly challenging since AS112 nodes are
   distributed using anycast [RFC4786].

   This document proposes a more flexibl approach for sinking queries on
   AS112 infrastructure that can be deployed alongside unmodified,
   existing AS112 nodes.  Instead of delegating additional zones
   directly to AS112 nameservers, DNAME [RFC6672] redirection is used
   instead.  This approach has the advantage that query traffic for
   arbitrary parts of the namespace can be directed to AS112 servers
   without those servers having to be reconfigured every time a zone is
   added or removed.

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2.  Design Overview

   A new zone, EMPTY.AS112.ARPA, is delegated to a single nameserver
   BLACKHOLE.AS112.ARPA (IPv4 address TBAv4-1, IPv6 address TBAv6-1).

   The IPv4 address TBAv4-1 has been assigned by the IANA such that the
   address is coverable by a single IPv4 /24 prefix, and that no other
   address covered by that prefix is in use.  The IPv6 address TBAv6-1
   has been similarly assigned such that no other address within a
   covering /48 is in use.  This addressing plan accommodates the
   anycast distribution of the BLACKHOLE.AS112.ARPA service using a
   single IPv4 service prefix and a single IPv6 service prefix.  See
   [RFC4786] for more discussion of anycast service distribution; see
   Section 8 for the specific requests this document makes of the IANA.

   Some or all of the existing AS112 nodes should be extended to support
   these new nameserver addresses, and to host the EMPTY.AS112.ARPA
   zone.  See [I-D.jabley-dnsop-rfc6304bis] for revised guidance to
   AS112 server operators.

   Each part of the DNS namespace for which it is desirable to sink
   queries at AS112 nameservers should be redirected to the
   EMPTY.AS112.ARPA zone using DNAME [RFC6672].  See Section 3.2 for
   guidance to zone administrators.

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3.  AS112 Operations

3.1.  Extensions to Support DNAME Redirection

   The guidance provided in [RFC6304] is extended to include
   configuration of the TBAv4-1, and TBAv6-1 addresses, and the
   corresponding announcement of covering routes for those addresses,
   and to host the EMPTY.AS112.ARPA zone.

   IPv4-only AS112 nodes should only configure the TBAv4-1 nameserver
   address; IPv6-only AS112 nodes should only configure the TBAv6-1
   nameserver address.

   It is only necessary for a single AS112 server operator to implement
   these extensions for this mechanism to function as intended.  It is
   beneficial if many more than one AS112 server operators make these
   changes, however, since that provides for greater distribution and
   capacity for the nameservers serving the EMPTY.AS112.ARPA zone.  It
   is not necessary for all AS112 server operators to make these changes
   for the mechanism to be viable.

   Detailed instructions for the implementation of these extensions is
   included in [I-D.jabley-dnsop-rfc6304bis].

3.2.  Redirection of Query Traffic to AS112 Servers

   Once the EMPTY.AS112.ARPA zone has been deployed using the
   nameservers described in Section 3.1, redirections may be installed
   in the DNS namespace for queries that are intended to be answered by
   the AS112 infrastructure.

   For example, reverse queries corresponding to TEST-NET-1
   ( [RFC5737] could be redirected to AS112 nameservers by
   installing a DNAME resource record in the 192.IN-ADDR.ARPA zone, as
   illustrated in Figure 1.


                                 Figure 1

   There is no practical limit to the number of redirections that can be
   configured in this fashion.  Redirection of a particular part of the
   namespace to EMPTY.AS112.ARPA can be removed at any time, under the
   control of the administrators of the corresponding part of the DNS
   namespace.  No changes to deployed AS112 nodes incorporating the

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   extensions described in this document are required to support
   additional redirections.  A list of possible candidates for AS112
   redirection can be found in Section 5.

   DNAME resource records deployed for this purpose can be signed with
   DNSSEC [RFC4033], providing a secure means of authenticating the
   legitimacy of each redirection.

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4.  Continuity of AS112 Operations

   Existing guidance to AS112 server operators to accept and respond to
   queries directed at the PRISONER.IANA.ORG, BLACKHOLE-1.IANA.ORG and
   BLACKHOLE-2.IANA.ORG nameservers should continue to be followed, and
   no changes to the delegation of existing zones hosted on AS112
   servers should occur.  These measures are intended to provide
   continuity of operations for zones currently delegated to AS112
   servers and avoid any accidental client impact due to the changes
   proposed in this document.

   Once it has become empirically and quantitatively clear that the
   EMPTY.AS112.ARPA zone is well-hosted to the extent that it is thought
   that the existing, unmodified AS112 servers host 10.IN-ADDR.ARPA, the
   decision might be made to replace the delegation of those [RFC1918]
   zones with DNAME redirection.  Once implemented, the
   nameservers could be retired.  This document gives no such direction
   to the IANA, however.

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5.  Candidate Zones for AS112 Redirection

   All zones listed in [RFC6303] are candidates for AS112 redirection.

   Since no pre-provisioning is required on the part of AS112 operators
   to facilitate sinking of any name in the DNS namespace by AS112
   infrastructure, this mechanism supports AS112 redirection by any zone
   owner in the DNS.

   This document is simply concerned with provision of the AS112
   redirection service, and does not specify that any particular AS112
   redirection be put in place.

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6.  DNAME Deployment Considerations

   DNAME was specified a significant time following the original
   implementations of [RFC1035], and hence universal deployment cannot
   be expected.  [RFC6672] specifies a fall-back mechanism which makes
   use of synthesised CNAME RRSets for this reason.  The expectation
   that design choices in the DNAME specification ought to mitigate any
   lack of deployment is reviewed below.  Experimental validation of
   those expectations is included in Appendix A.

   It is a fundamental design requirement of AS112 service that
   responses be cached.  We can safely declare DNAME support on the
   authoritative server to be a prerequisite for DNAME redirection, but
   the cases where individual elements in resolver chains do not support
   DNAME processing deserve closer examination.

   The expected behaviour when a DNAME response is supplied to a
   resolver that does not support DNAME is that the accompanying,
   synthesised CNAME will be accepted and cached.  Re-query frequency
   will be determined by the TTLs returned by the DNAME-responding
   authoritative servers.

   Resolution of the CNAME target is straightforward and functions
   exactly as the AS112 project has operated since it was deployed.  The
   negative caching [RFC2308] of the CNAME target follows the parameters
   defined in the target zone, EMPTY.AS112.ARPA.  This has the side-
   effects that all redirected names ultimately landing on an AS112 node
   will be negatively-cached with the same parameters, but this lack of
   flexibility seems non-controversial; the effect of reducing the
   negative cache TTL would be increased query volume on the AS112 node
   operator concerned, and hence controls seem well-aligned with

   Validating resolvers (i.e. those requesting and processing DNSSEC
   [RFC4033] metadata) are required to implement DNAME, and hence should
   not make use of synthesised CNAME RRs.  The lack of signature over a
   received CNAME RR should hence not limit the ability to sign the
   redirection point, and for those signatures to be validated.

   In the case where a recursive server implements DNAME, but DNAME is
   not implemented in a stub resolver, CNAME synthesis will again
   provide a viable path.

   DNAME support on AS112 nodes themselves is never required under this

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7.  IAB Considerations

   This document proposes a delegation within the ARPA domain, and, in
   accordance with [RFC3172], IAB review and approval of the delegation
   of AS112.ARPA as described in Section 8 is required.

   Once IAB approval has been obtained, this section may be removed
   prior to publication or updated to include text that confirms the
   IAB's decision, at the IAB's discretion.

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8.  IANA Considerations

8.1.  Address Assignment

   The IANA is requested to assign one IPv4 /24 netblock and one IPv6
   /48 netblock that, to the best of their knowledge, should be suitable
   for announcement as a single IPv4 /24 prefix and a single IPv6 prefix
   on the global Internet, respectively.

   Once assigned, all occurrences of TBAv4 in this document should be
   replaced by the IPv4 netblock assigned, in conventional notation.
   Occurrences of TBAv4-1 should be replaced with an address from the
   netblock with lowest octet set to 1.  Similarly, all occurrences of
   TBAv6 in this document should be replaced by the IPv6 netblock
   assigned, in conventional notation, and TBAv6-1 replaced with an
   address from that netblock with the lowest 48 bits set to the value
   1.  Once those changes are made, this paragraph may be removed prior
   to publication.

   The netblocks assigned by the IANA for this purpose are TBAv4 and

8.2.  Hosting of AS112.ARPA

   The IANA is requested to host and sign the zone AS112.ARPA using
   nameservers and DNSSEC signing infrastructure of their choosing, as
   shown in Figure 2.  SOA RDATA may be adjusted by the IANA to suit
   their operational requirements.

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    $TTL 3600

    @       IN      SOA     BLACKHOLE.AS112.ARPA. NOC.DNS.ICANN.ORG. (
                                    1               ; serial
                                    10800           ; refresh
                                    3600            ; retry
                                    1209600         ; expire
                                    3600 )          ; negative cache TTL

                    NS      A.IANA-SERVERS.NET.
                    NS      B.IANA-SERVERS.NET.
                    NS      C.IANA-SERVERS.NET.

    BLACKHOLE       A       TBAv4-1
                    AAAA    TBAv6-1


    EMPTY           NS      BLACKHOLE

                                 Figure 2

8.3.  Delegation of AS112.ARPA

   Once the AS112.ARPA zone is being hosted in production, the IANA is
   requested to arrange delegation from the ARPA zone according to
   normal IANA procedure for ARPA zone management, to the nameservers
   used in carrying out the direction in Section 8.2.  The following
   metadata is suggested for the delegation, but may be changed by the
   IANA if required:

   | Name           | Value                                            |
   | Domain:        | AS112.ARPA                                       |
   |                |                                                  |
   | Administrative | Internet Architecture Board (IAB) c/o IETF       |
   | Contact:       | Administrative Support Activity, ISOC            |
   |                |                                                  |
   | Technical      | Internet Assigned Numbers Authority (IANA)       |
   | Contact:       |                                                  |
   |                |                                                  |
   | Nameservers:   | As chosen by the IANA, see Section 8.2           |
   |                |                                                  |
   | DS-RDATA:      | As chosen by the IANA, see Section 8.2           |

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9.  Security Considerations

   This document presents no known additional security concerns to the

   For security considerations relating to AS112 service in general, see

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10.  Acknowledgements

   Your name here, etc.

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11.  References

11.1.  Normative References

              Abley, J. and W. Maton, "AS112 Nameserver Operations",
              draft-jabley-dnsop-rfc6304bis-00 (work in progress),
              February 2014.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

   [RFC2308]  Andrews, M., "Negative Caching of DNS Queries (DNS
              NCACHE)", RFC 2308, March 1998.

   [RFC6304]  Abley, J. and W. Maton, "AS112 Nameserver Operations",
              RFC 6304, July 2011.

   [RFC6672]  Rose, S. and W. Wijngaards, "DNAME Redirection in the
              DNS", RFC 6672, June 2012.

11.2.  Informative References

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

   [RFC3172]  Huston, G., "Management Guidelines & Operational
              Requirements for the Address and Routing Parameter Area
              Domain ("arpa")", BCP 52, RFC 3172, September 2001.

   [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "DNS Security Introduction and Requirements",
              RFC 4033, March 2005.

   [RFC4786]  Abley, J. and K. Lindqvist, "Operation of Anycast
              Services", BCP 126, RFC 4786, December 2006.

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

   [RFC6303]  Andrews, M., "Locally Served DNS Zones", BCP 163,
              RFC 6303, July 2011.

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Appendix A.  Assessing Support for DNAME in the Real World

   To measure the extent to which the DNAME construct is supported in
   the Internet, we have used an experimental technique to test the DNS
   resolvers used by end hosts, and derive from the test a measurement
   of DNAME support within the Internet.

A.1.  Methodology

   The test was conducted by loading a user's browser with 4 URLs to
   retrieve.  The first three comprise the test setup, while the final
   URL communicates the result the the experiment controller.  The URLs

   A  http://a.<unique_string>.dname.example.com/1x1.png?

   B  http://b.dname.example.com/1x1.png?

   C  http://c.<unique_string>.target.example.net/1x1.png?

   D  http://results.recorder.example.net/1x1.png?

   The A URL is designed to test the end users capability to resolve a
   name that has never been seen before, so that the resolution of this
   domain name will reliably result in a query at the authoritative name
   server.  This is intended to test the use of domain names where there
   is a dynamic component that also uses the DNAME construct.

   The B URL is deliberately designed to be cached by caching resolvers
   that are used in the process of resolving the domain name.

   The C URL is a control URL.  This is a unique URL, similar to A, but
   does not refer to a DNAME structure.

   The D URL uses a static cacheable domain name.

   The <unique_string> value is common to the four URLs used in each
   individual instance of this test, but varies from test to test.  The
   result is that each end user is presented with a unique string.

   The contents of the EXAMPLE.COM, TARGET.EXAMPLE.NET and
   RECORDER.EXAMPLE.NET zones are shown in Figure 3.

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     B                  IN  A
     *                  IN  A

     RESULTS            IN  A

                                 Figure 3

   The first three URLs (A, B and C) are loaded as tasks into the user's
   browser upon execution of the test's script.  The script starts a
   timer with each of these URLs to measure the elapsed time to fetch
   the URL.  The script then waits for the three fetches to complete, or
   10 seconds, whichever occurs first.  The script then loads the
   results of the three timers into the GET arguments of the D URL, and
   performs a fetch to pass these results back to the experiment's

   Logs on the web server reached at RESULTS.EXAMPLE.NET will include
   entries of the form shown in Figure 4.  If any of the URLs fail to
   load within 10 secords the D URL will report the failure as a "null"
   timer value.

     GET /1x1.png?results.<unique_string>?za=1822&zb=1674&zc=1582
     GET /1x1.png?results.<unique_string>?za=null&zb=null&zc=161

                                 Figure 4

   The script has been encoded in Adobe Flash with a simple image in the
   form of an online advertisement.  An online advertisement network has
   been used to distribute the script.  The script is invoked when the
   advertisement is presented in the end user's browser or application,
   and does not require the user to click on the supplied image in any
   way.  The advertisement placement parameters were set to to broadest
   possible scope to sample users from across the entire internet.

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A.2.  Results

   The test was loaded into an advertisement distributed on the
   2013-10-10 and 2013-10-11.

               |                    |   Count | Percentage |
               | Recorded Results:  | 338,478 |            |
               |                    |         |            |
               | A or B Loaded:     | 331,896 |      98.1% |
               |                    |         |            |
               | A Fail and B Fail: |   6,492 |       1.9% |
               |                    |         |            |
               | A Fail and B Load: |   4,249 |       1.3% |
               |                    |         |            |
               | A Load and B Fail: |   1,624 |       0.5% |
               |                    |         |            |
               | C Fail:            |   9,355 |       2.8% |

                                  Table 1

   These results indicate that at most 1.9% of tested clients use DNS
   resolvers that fail to resolve a domain name that contains a DNAME
   redirection.  However the failure rate of slightly lower than 3% for
   the control URL indicates that the failure rate for the DNAME
   construct lies within the bounds of error within the experimental
   framework.  We conclude that there is no evidence of a consistent
   failure on the part of deployed DNS resolvers to correctly resolve a
   DNAME construct.

   This experiment was conducted by Geoff Huston and George Michaelson.

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Appendix B.  Editorial Notes

   This section (and sub-sections) to be removed prior to publication.

B.1.  Change History

   00 Initial write-up of Brian's idea, circulated for the purposes of

   01 Some particularly egregious spelling mistakes fixed.  Warren
      Kumari and George Michaelson added as co-authors.  Intended status
      changed to informational.  Appendix on DNAME testing added,
      describing an experiment conducted by Geoff Huston and George

   00 Adopted by dnsop in IETF88, Vancouver; resubmitted as
      draft-ietf-dnsop-as112-dname.  Changed contact info for Brian.

   01 Minor updates following submission of

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Authors' Addresses

   Joe Abley
   Dyn, Inc.
   470 Moore Street
   London, ON  N6C 2C2

   Phone: +1 519 670 9327
   Email: jabley@dyn.com

   Brian Dickson
   Verisign Labs
   12061 Bluemont Way
   Reston, VA  20190

   Email: bdickson@verisign.com

   Warren Kumari
   1600 Amphitheatre Parkway
   Mountain View, CA  94043

   Email: warren@kumari.net

   George Michaelson

   Email: ggm@apnic.net

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