DNS Operations                                                W. Mekking
Internet-Draft                                                D. Mahoney
Intended status: Informational                                       ISC
Expires: January 27, 2020                                  July 26, 2019

      Moving DNSSEC Lookaside Validation (DLV) to Historic Status


   This document obsoletes DNSSEC lookaside validation (DLV) and
   reclassifies RFCs 4431 and 5074 as Historic.

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Table of Contents

   1.  Introduction
   2.  Discussion
   3.  Moving DLV to Historic Status
     3.1.  Documents that reference the DLV RFCs
       3.1.1.  Documents that reference RFC 4431
       3.1.2.  Documents that reference RFC 5074
   4.  IANA Considerations
   5.  Security considerations
   6.  Acknowledgements
   7.  Normative References
   Authors' Addresses

1.  Introduction

   DNSSEC Lookaside Validation (DLV) was introduced to assist with the
   adoption of DNSSEC [RFC4033] [RFC4034] [RFC4035] in a time where the
   root zone and many top level domains (TLDs) were unsigned, to help
   entities with signed zones under an unsigned parent zone, or that
   have registrars that don't accept DS records.  The root zone is
   signed since July 2010 and as of May 2019, 1389 out of 1531 TLDs have
   a secure delegation from the root; thus DLV has served its purpose
   and can now retire.

2.  Discussion

   One could argue that DLV is still useful because there are still some
   unsigned TLDs and entities under those zones will not benefit from
   signing their zone.  However, keeping the DLV mechanism also has

   o  It reduces the pressure to get the parent zone signed.

   o  It reduces the pressure on registrars to accept DS records.

   o  It complicates validation code.

   In addition, not every validator actually implements DLV (only BIND 9
   and Unbound) so even if an entity can use DLV to set up an alternate
   path to its trust anchor, its effect is limited.  Furthermore, there
   was one well-known DLV registry (dlv.isc.org) and that has been
   deprecated (replaced with a signed empty zone) on September 30, 2017.
   With the absence of a well-known DLV registry service it is unlikely
   that there is a real benefit for the protocol on the Internet

   One other possible reason to keep DLV is to distribute trust anchors
   for private enterprises.  The authors are not aware of any such use
   of DLV.

   All things considered it is probably not worth the effort of
   maintaining the DLV mechanism.

3.  Moving DLV to Historic Status

   There are two RFCs that specify DLV:

   1.  RFC 4431 [RFC4431] specifies the DLV resource record.

   2.  RFC 5074 [RFC5074] specifies the DLV mechanism for publishing
       trust anchors outside the DNS delegation chain and how validators
       can use them to validate DNSSEC-signed data.

   This document moves both RFC 4431 [RFC4431] and RFC 5074 [RFC5074] to
   Historic status.  This is a clear signal to implementers that the DLV
   resource record and the DLV mechanism SHOULD NOT be implemented or

3.1.  Documents that reference the DLV RFCs

   The RFCs that are being moved to Historic status are referenced by a
   couple of other documents.  The sections below describe what changes
   when the DLV RFCs have been reclassified as Historic.

3.1.1.  Documents that reference RFC 4431

   One RFC makes reference to RFC 4431 [RFC4431].  RFC 5074

   RFC 5074 [RFC5074], "DNSSEC Lookaside Validation (DLV)" describes the
   DLV mechanism itself, and is being moved to Historic status too.

3.1.2.  Documents that reference RFC 5074

   Three RFCs make reference to RFC 5074 [RFC5074].  RFC 6698

   RFC 6698, "The DNS-Based Authentication of Named Entities (DANE)
   Transport Layer Security (TLS) Protocol: TLSA" [RFC6698] specifies:

   DNSSEC forms certificates (the binding of an identity to a key) by
   combining a DNSKEY, DS, or DLV resource record with an associated
   RRSIG record.  These records then form a signing chain extending from
   the client's trust anchors to the RR of interest.

   This document updates RFC 6698 to exclude the DLV resource record
   from certificates.  RFC 6840

   RFC 6840, "Clarifications and Implementation Notes for DNS Security
   (DNSSEC)" [RFC6840] says that when trust anchors come from different
   sources, a validator may choose between them based on the perceived
   reliability of those sources.  But in reality this does not happen in
   validators (both BIND 9 and Unbound have a option for a DLV trust
   anchor that can be used solely as a fallback).

   This document updates RFC 6840 to exclude the DLV registries from the
   trust anchor selection.  RFC 8198

   RFC 8198, "Aggressive Use of DNSSEC-Validated Cache" [RFC8198] only
   references RFC 5074 because aggressive negative caching was first
   proposed there.

4.  IANA Considerations

   IANA should update the annotation of the DLV RR type (code 32769) to
   "Obsolete" in the DNS Parameters registry.

5.  Security considerations

   When the DLV mechanism goes away, zones that rely on DLV for their
   validation will be treated as insecure.  The chance that this
   scenario actually occurs is very low, since no well-known DLV
   registry exists.

6.  Acknowledgements

   Ondrej Sury for initial review.

7.  Normative References

   [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "DNS Security Introduction and Requirements",
              RFC 4033, DOI 10.17487/RFC4033, March 2005,

   [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Resource Records for the DNS Security Extensions",
              RFC 4034, DOI 10.17487/RFC4034, March 2005,

   [RFC4035]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Protocol Modifications for the DNS Security
              Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,

   [RFC4431]  Andrews, M. and S. Weiler, "The DNSSEC Lookaside
              Validation (DLV) DNS Resource Record", RFC 4431,
              DOI 10.17487/RFC4431, February 2006,

   [RFC5074]  Weiler, S., "DNSSEC Lookaside Validation (DLV)", RFC 5074,
              DOI 10.17487/RFC5074, November 2007,

   [RFC6698]  Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
              of Named Entities (DANE) Transport Layer Security (TLS)
              Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August
              2012, <https://www.rfc-editor.org/info/rfc6698>.

   [RFC6840]  Weiler, S., Ed. and D. Blacka, Ed., "Clarifications and
              Implementation Notes for DNS Security (DNSSEC)", RFC 6840,
              DOI 10.17487/RFC6840, February 2013,

   [RFC8198]  Fujiwara, K., Kato, A., and W. Kumari, "Aggressive Use of
              DNSSEC-Validated Cache", RFC 8198, DOI 10.17487/RFC8198,
              July 2017, <https://www.rfc-editor.org/info/rfc8198>.

Authors' Addresses

   Matthijs Mekking
   950 Charter St
   Redwood City, CA  94063

   Email: matthijs@isc.org

   Dan Mahoney
   950 Charter St
   Redwood City, CA  94063

   Email: dmahoney@isc.org