| RFC 8749 | Obsolete DLV | March 2020 |
| Mekking & Mahoney | Standards Track | [Page] |
This document retires DNSSEC Lookaside Validation (DLV) and reclassifies RFCs 4431 and 5074 as Historic. Furthermore, this document updates RFC 6698 by excluding the DLV resource record from certificates and updates RFC 6840 by excluding the DLV registries from the trust anchor selection.¶
This is an Internet Standards Track document.¶
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.¶
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8749.¶
Copyright (c) 2020 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 Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.¶
DNSSEC Lookaside Validation (DLV) was introduced to assist with the adoption of DNSSEC [RFC4033] [RFC4034] [RFC4035] in a time when the root zone and many top-level domains (TLDs) were unsigned. DLV allowed entities with signed zones under an unsigned parent zone or entities with registrars that did not accept DS records to publish trust anchors outside of the normal DNS delegation chain. The root zone was signed in 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.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
One could argue that DLV is still useful because there are still some unsigned TLDs and entities under those zones that will not benefit from signing their zone. However, keeping the DLV mechanism also has disadvantages:¶
In addition, not every validator actually implemented 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), which was 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 nowadays.¶
One other possible reason to keep DLV is to distribute trust anchors for private enterprises. There are no known uses of DLV for this.¶
All things considered, it is probably not worth the effort of maintaining the DLV mechanism.¶
There are two RFCs that specify DLV:¶
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 deployed.¶
The RFCs being moved to Historic status are referenced by a couple of other RFCs. The sections below describe the changes to those documents due to the DLV RFCs being reclassified as Historic.¶
Three RFCs make reference to RFC 5074 [RFC5074].¶
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 [RFC6698] to exclude the DLV resource record from certificates.¶
RFC 6840 ("Clarifications and Implementation Notes for DNS Security (DNSSEC)") [RFC6840] states 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 an option for a DLV trust anchor that can be used solely as a fallback).¶
This document updates RFC 6840 [RFC6840] to exclude the DLV registries from the trust anchor selection.¶
IANA has updated the annotation of the DLV RR type (code 32769) to "Obsolete" in the "Domain Name System (DNS) Parameters" registry.¶
Once the DLV mechanism is retired, 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.¶
The authors thank Ondřej Surý for the initial review.¶