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.
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:
- RFC 4431 specifies the
DLV resource record.
- 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
Acknowledgements
The authors thank for the initial review.