Moving DNSSEC Lookaside Validation (DLV) to Historic Status ISC
Netherlands matthijs@isc.org
ISC
US dmahoney@isc.org
Operations and Management DNS Operations DNS DNSSEC DLV 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.
Status of This Memo 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 .
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Table of Contents
  • .  Introduction
  • .  Requirements Language
  • .  Discussion
  • .  Moving DLV to Historic Status
    • .  Documents That Reference the DLV RFCs
      • .  Documents That Reference RFC 4431
      • .  Documents That Reference RFC 5074
  • .  IANA Considerations
  • .  Security Considerations
  • .  Normative References
  • Acknowledgements
  • Authors' Addresses
Introduction DNSSEC Lookaside Validation (DLV) was introduced to assist with the adoption of DNSSEC 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.
Requirements Language 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 when, and only when, they appear in all capitals, as shown here.
Discussion 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:
  • It reduces the pressure to get the parent zone signed.
  • It reduces the pressure on registrars to accept DS records.
  • It complicates validation code.
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.
Moving DLV to Historic Status There are two RFCs that specify DLV:
  1. RFC 4431 specifies the DLV resource record.
  2. RFC 5074 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 and RFC 5074 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.
Documents That Reference the DLV RFCs 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.
Documents That Reference RFC 4431 One RFC makes reference to RFC 4431 .
RFC 5074 RFC 5074 ("DNSSEC Lookaside Validation (DLV)") describes the DLV mechanism itself. This document moves RFC 5074 to Historic status as well.
Documents That Reference RFC 5074 Three RFCs make reference to RFC 5074 .
RFC 6698 RFC 6698 ("The DNS-Based Authentication of Named Entities (DANE) Transport Layer Security (TLS) Protocol: TLSA") 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)") 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 to exclude the DLV registries from the trust anchor selection.
RFC 8198 RFC 8198 ("Aggressive Use of DNSSEC-Validated Cache") only references RFC 5074 because aggressive negative caching was first proposed there.
IANA Considerations IANA has updated the annotation of the DLV RR type (code 32769) to "Obsolete" in the "Domain Name System (DNS) Parameters" registry.
Security Considerations 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.
Normative References Key words for use in RFCs to Indicate Requirement Levels In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. DNS Security Introduction and Requirements The Domain Name System Security Extensions (DNSSEC) add data origin authentication and data integrity to the Domain Name System. This document introduces these extensions and describes their capabilities and limitations. This document also discusses the services that the DNS security extensions do and do not provide. Last, this document describes the interrelationships between the documents that collectively describe DNSSEC. [STANDARDS-TRACK] Resource Records for the DNS Security Extensions This document is part of a family of documents that describe the DNS Security Extensions (DNSSEC). The DNS Security Extensions are a collection of resource records and protocol modifications that provide source authentication for the DNS. This document defines the public key (DNSKEY), delegation signer (DS), resource record digital signature (RRSIG), and authenticated denial of existence (NSEC) resource records. The purpose and format of each resource record is described in detail, and an example of each resource record is given. This document obsoletes RFC 2535 and incorporates changes from all updates to RFC 2535. [STANDARDS-TRACK] Protocol Modifications for the DNS Security Extensions This document is part of a family of documents that describe the DNS Security Extensions (DNSSEC). The DNS Security Extensions are a collection of new resource records and protocol modifications that add data origin authentication and data integrity to the DNS. This document describes the DNSSEC protocol modifications. This document defines the concept of a signed zone, along with the requirements for serving and resolving by using DNSSEC. These techniques allow a security-aware resolver to authenticate both DNS resource records and authoritative DNS error indications. This document obsoletes RFC 2535 and incorporates changes from all updates to RFC 2535. [STANDARDS-TRACK] The DNSSEC Lookaside Validation (DLV) DNS Resource Record This document defines a new DNS resource record, called the DNSSEC Lookaside Validation (DLV) RR, for publishing DNSSEC trust anchors outside of the DNS delegation chain. This memo provides information for the Internet community. DNSSEC Lookaside Validation (DLV) DNSSEC Lookaside Validation (DLV) is a mechanism for publishing DNS Security (DNSSEC) trust anchors outside of the DNS delegation chain. It allows validating resolvers to validate DNSSEC-signed data from zones whose ancestors either aren't signed or don't publish Delegation Signer (DS) records for their children. This memo provides information for the Internet community. The DNS-Based Authentication of Named Entities (DANE) Transport Layer Security (TLS) Protocol: TLSA Encrypted communication on the Internet often uses Transport Layer Security (TLS), which depends on third parties to certify the keys used. This document improves on that situation by enabling the administrators of domain names to specify the keys used in that domain's TLS servers. This requires matching improvements in TLS client software, but no change in TLS server software. [STANDARDS-TRACK] Clarifications and Implementation Notes for DNS Security (DNSSEC) This document is a collection of technical clarifications to the DNS Security (DNSSEC) document set. It is meant to serve as a resource to implementors as well as a collection of DNSSEC errata that existed at the time of writing. This document updates the core DNSSEC documents (RFC 4033, RFC 4034, and RFC 4035) as well as the NSEC3 specification (RFC 5155). It also defines NSEC3 and SHA-2 (RFC 4509 and RFC 5702) as core parts of the DNSSEC specification. Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Aggressive Use of DNSSEC-Validated Cache The DNS relies upon caching to scale; however, the cache lookup generally requires an exact match. This document specifies the use of NSEC/NSEC3 resource records to allow DNSSEC-validating resolvers to generate negative answers within a range and positive answers from wildcards. This increases performance, decreases latency, decreases resource utilization on both authoritative and recursive servers, and increases privacy. Also, it may help increase resilience to certain DoS attacks in some circumstances. This document updates RFC 4035 by allowing validating resolvers to generate negative answers based upon NSEC/NSEC3 records and positive answers in the presence of wildcards.
Acknowledgements The authors thank for the initial review.
Authors' Addresses ISC
Netherlands matthijs@isc.org
ISC
US dmahoney@isc.org