As required by RFC 4858, this is the current template for the Document
Shepherd Write-Up. Changes are expected over time.
This version is dated 1 November 2019.
(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. This is the right target due to the scope, content, and intent of the work. It is properly indicated in the header.
(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 document describes a robust method for Path MTU Discovery
(PMTUD) for datagram Packetization Layers (PLs). It describes an
extension to RFC 1191 and RFC 8201, which specifies ICMP-based Path
MTU Discovery for IPv4 and IPv6. The method allows a PL, or a
datagram application that uses a PL, to discover whether a network
path can support the current size of datagram. This can be used to
detect and reduce the message size when a sender encounters a packet
black hole (where packets are discarded). The method can probe a
network path with progressively larger packets to discover whether
the maximum packet size can be increased. This allows a sender to
determine an appropriate packet size, providing functionality for
datagram transports that is equivalent to the Packetization Layer
PMTUD specification for TCP, specified in RFC 4821.
The document updates RFC 4821 to specify the method for datagram PLs,
and updates RFC 8085 as the method to use in place of RFC 4821 with
UDP datagrams. Section 7.3 of RFC4960 recommends an endpoint apply
the techniques in RFC4821 on a per-destination-address basis.
RFC4960 is updated to recommend that SCTP uses the method specified
in this document instead of the method in RFC4821.
The document also provides implementation notes for incorporating
Datagram PMTUD into IETF datagram transports or applications that use
When published, this specification updates RFC 4821, RFC 4960 and RFC 8085.
Working Group Summary:
There were no major controversies or points of questionable consensus in the process of working on this document. The document is somewhat related to work in other working groups (such as QUIC), since it lays out the framework for path MTU discovery that can be used in any datagram-based protocol.
There have been a number of separate implementations at different stages of the document's maturity. An implementation for SCTP targets the FreeBSD kernel, and is starting the review process to be included.
This code also is the basis for a userland stack currently used in browsers for WebRTC data channels.
Another implementation with UDP options was done for the FreeBSD kernel, though has not tracked the draft since 2018. Three early implementations were also done as part of the EU MAMI project, to test possible algorithms and check if the specification could be implemented, but these did not enter production code. Two of these implementations were with UDP application protocols, for testing, and the third was for a QUIC implementation.
Wesley Eddy is the document shepherd. Magnus Westerlund is the responsible AD.
(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 the IESG.
I have done a full review of the document, and believe it is ready for publication.
(4) Does the document Shepherd have any concerns about the depth or breadth of the reviews that have been performed?
(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 took place.
No additional special reviews are needed.
(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 concerns here.
(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?
(8) Has an IPR disclosure been filed that references this document? If so, summarize any WG discussion and conclusion regarding the IPR disclosures.
No IPR disclosures.
(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?
(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.)
No possible appeals mentioned.
(11) Identify any ID nits the Document Shepherd has found in this document. (See http://www.ietf.org/tools/idnits/ and the Internet-Drafts Checklist). Boilerplate checks are not enough; this check needs to be thorough.
There are a few erroneous idnits warnings about the Updates header based on the abstract. I think this is because the header was truncated, and should be fixed by the RFC Editor if needed.
(12) Describe how the document meets any required formal review criteria, such as the MIB Doctor, YANG 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?
There is a normative reference to the QUIC specification, which is still an I-D (not yet published as an RFC). This is fine, because it should block this document in the RFC Editor queue waiting for that reference to be resolved.
(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.
No RFCs are obsoleted, and the three that are updated are noted in the header, explained in the abstract, and discussed properly in the document. The 4960 update is discussed in the later section specific to SCTP (which is appropriate) and not in the introduction, but the other two documents updated are discussed clearly in the introduction.
(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 IANA requests.
(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, YANG modules, etc.
(20) If the document contains a YANG module, has the module been checked with any of the recommended validation tools (https://trac.ietf.org/trac/ops/wiki/yang-review-tools) for syntax and formatting validation? If there are any resulting errors or warnings, what is the justification for not fixing them at this time? Does the YANG module comply with the Network Management Datastore Architecture (NMDA) as specified in RFC8342?