As required by RFC 4858, this is the current template for the Document
Changes are expected over time. This version is dated 24 February 2012.
(1) What type of RFC is being requested (BCP, Proposed Standard,
Internet Standard, Informational, Experimental, or Historic)? Why
is this the proper type of RFC? Is this type of RFC indicated in the
title page header?
Proposed standard. It updates the definition of TTL in RFC 1034, 1035, and 2181.
(2) The IESG approval announcement includes a Document Announcement
Write-Up. Please provide such a Document Announcement Write-Up. Recent
examples can be found in the "Action" announcements for approved
documents. The approval announcement contains the following sections:
This draft defines a method (serve-stale) for recursive resolvers to
use stale DNS data to avoid outages when authoritative nameservers
cannot be reached to refresh expired data. It updates the definition
of TTL from RFCs 1034, 1035, and 2181 to make it clear that
data can be kept in the cache beyond the TTL expiry and used for
responses when a refreshed answer is not readily available. (From the Abstract.)
Working Group Summary
This draft dates to March 2017 and was adopted by DNSOP in October 2017. It's been extensively reviewed in the WG. The primary point of controversy was that it discusses an optional protocol change (the choice by a recursive resolver to re-use data beyond the authoritative server TTL when no refresh is available) that some WG participants felt to be unwise under some conditions. The discussion of timer values in Sec. 5, and of implementation decisions and caveats in Sec. 6 and Sec. 7, seem to address these concerns. Since this protocol modification is widely implemented and deployed, having a standards track description seemed to promote careful practice and interoperability.
The protocol update discussed in this draft is an attempt to document behavior that is implemented in multiple open source DNS codebases and deployed by a number of large operators, including DNS services and CDNs that rely on the specified DNS behavior. Common practice regarding the handling of TTLs by recursive resolvers has changed considerably over the behavior originally specified, and documenting the current practice as an update to the protocol seems likely to promote interoperability and transparency under both normal and adverse conditions.
Who is the Document Shepherd? Who is the Responsible Area
Suzanne Woolf (shepherd)
Barry Leiba (AD; the WG's AD, Warren Kumari, is an author.)
(3) Briefly describe the review of this document that was performed by
the Document Shepherd. If this version of the document is not ready
for publication, please explain why the document is being forwarded to
There are some minor issues (typos, minor copyedits) but this document is ready for IESG review. (-07)
(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed?
No. The WG core of participants are exactly the people to review this, based on protocol knowledge, implementation experience, and operational experience.
(5) Do portions of the document need review from a particular or from
broader perspective, e.g., security, operational complexity, AAA, DNS,
DHCP, XML, or internationalization? If so, describe the review that
(6) Describe any specific concerns or issues that the Document Shepherd
has with this document that the Responsible Area Director and/or the
IESG should be aware of? For example, perhaps he or she is uncomfortable
with certain parts of the document, or has concerns whether there really
is a need for it. In any event, if the WG has discussed those issues and
has indicated that it still wishes to advance the document, detail those
From time to time, DNSOP considers documents that describe DNS behavior that might be controversial, or whose costs and benefits are not universally agreed on. In those situations, sometimes the WG has to decide whether they feel that the documented behavior is harmful, and if so whether documenting it encourages or limits the harm. Some discussion along those lines occurred around this document. The chairs believe the concerns were addressed and there is consensus to advance the document.
(7) Has each author confirmed that any and all appropriate IPR
disclosures required for full conformance with the provisions of BCP 78
and BCP 79 have already been filed. If not, explain why.
All authors have confirmed.
(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR
There are several IPR disclosures. In all three cases of specific disclosures, the companies responsible have affirmed they're granting licenses for any use of their technology in the implementation of this draft.
(9) How solid is the WG consensus behind this document? Does it
represent the strong concurrence of a few individuals, with others
being silent, or does the WG as a whole understand and agree with it?
This document seems to be supported by multiple implementers and operators as reflecting current or planned practice, with the benefits and caveats described.
(10) Has anyone threatened an appeal or otherwise indicated extreme
discontent? If so, please summarise the areas of conflict in separate
email messages to the Responsible Area Director. (It should be in a
separate email because this questionnaire is publicly available.)
(11) Identify any ID nits the Document Shepherd has found in this
document. (See https://www.ietf.org/tools/idnits/ and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be
There are a number of update_references warnings from idnits. Some are hard to parse (they flag external references e.g. [DikeBreaks]). Many are due to the extensive discussion of changes in meaning of terms now considered RFC2119-normative as used in a much older RFC (1034). The warning about an improper URL is spurious (it's a live URL, not an example, and it's in an "Implementation Experience" section that will be removed prior to publication.)
(12) Describe how the document meets any required formal review
criteria, such as the MIB Doctor, media type, and URI type reviews.
(13) Have all references within this document been identified as
either normative or informative?
(14) Are there normative references to documents that are not ready for
advancement or are otherwise in an unclear state? If such normative
references exist, what is the plan for their completion?
(15) Are there downward normative references references (see RFC 3967)?
If so, list these downward references to support the Area Director in
the Last Call procedure.
(16) Will publication of this document change the status of any
existing RFCs? Are those RFCs listed on the title page header, listed
in the abstract, and discussed in the introduction? If the RFCs are not
listed in the Abstract and Introduction, explain why, and point to the
part of the document where the relationship of this document to the
other RFCs is discussed. If this information is not in the document,
explain why the WG considers it unnecessary.
This document updates RFCs 1034, 1035, and 2181. The shepherd believes the intended effect is clear.
(17) Describe the Document Shepherd's review of the IANA considerations
section, especially with regard to its consistency with the body of the
document. Confirm that all protocol extensions that the document makes
are associated with the appropriate reservations in IANA registries.
Confirm that any referenced IANA registries have been clearly
identified. Confirm that newly created IANA registries include a
detailed specification of the initial contents for the registry, that
allocations procedures for future registrations are defined, and a
reasonable name for the new registry has been suggested (see RFC 8126).
There are no actions for IANA in this document, and it has no impact on the meaning of any existing IANA registry or allocated codepoint. It updates the use of a field in DNS RRs as defined in the original specification but requires no change to that definition.
(18) List any new IANA registries that require Expert Review for future
allocations. Provide any public guidance that the IESG would find
useful in selecting the IANA Experts for these new registries.
(19) Describe reviews and automated checks performed by the Document
Shepherd to validate sections of the document written in a formal
language, such as XML code, BNF rules, MIB definitions, etc.