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Shepherd writeup

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 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?
SHEPHERD RESPONSE:  Proposed Standard.
This is the proper type of RFC because the document mandates protocol behavior
for a fragment forwarding technique that avoids per-hop reassembly in 6LoWPAN
multihop networks. (In addition, it provides an overview of the benefits and
limitations of two approaches for fragment forwarding in 6LoWPAN multihop

(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:

Technical Summary

   This document introduces the capability to forward 6LoWPAN fragments.
   This method reduces the latency and increases end-to-end reliability
   in route-over forwarding.  It is the companion to using virtual
   reassembly buffers which is a pure implementation technique.

Working Group Summary

  Was there anything in WG process that is worth noting? For
  example, was there controversy about particular points or
  were there decisions where the consensus was particularly


The topic of fragmentation attracted increased interest from participants at
the 6lo working group in 2016-2017, with dedicated fragmentation discussion
slots in 6lo at IETF 98 and IETF 99. As a result, a fragmentation Design Team
was formed. It was decided that two 6lo wg documents and one lwig wg document
would be created, more specifically: a) a document defining a fragment recovery
protocol (i.e. the document that is the object of this writeup), b) an
informational document giving an overview of minimal fragment forwarding, and
c) a document describing the implementation technique that avoids per-hop
packet fragmentation and reassembly. The present document is the second one.
This decision had good consensus, and the present document was created and has
progressed with no controversy. Only after the review of -04 by the INTDIR
assigned reviewer (Dave Thaler), and subsequent discussion with the authors, it
has become clear that some content of the document had to mandate protocol
behavior, thus the Intended Status of Proposed Standard.

Document Quality

  Are there existing implementations of the protocol? Have a
  significant number of vendors indicated their plan to
  implement the specification?
There exist implementations of the fragment forwarding technique that avoids
per-hop reassembly.

   Are there any reviewers that
  merit special mention as having done a thorough review,
  e.g., one that resulted in important changes or a
  conclusion that the document had no substantive issues?

Yasuyuki Tanaka, Georgios Papadopoulos and Dominique Barthel carried out deep
reviews. The last two were carried out during WGLC, and the comments were
addressed in draft-ietf-6lo-minimal-fragment-02. Dave Thaler reviewed -04, on
behalf of the INTDIR, and subsequent discussion with the authors led to adding
normative text to the document and changing its intended status from
Informational to Proposed Standard.

 If  there was a MIB Doctor, Media Type or other expert review,
  what was its course (briefly)? In the case of a Media Type
  review, on what date was the request posted?



Document Shepherd: Carles Gomez
Responsible Area Director: Suresh Krishnan

(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.
The shepherd initially reviewed revision -02 of the document. A few suggestions
were made and the document was updated in -03 (e.g. using “6LoWPAN” instead of
“LLN”, use of the term “minimal” was removed from the text, etc.).
Subsequently, a WG participant made questions that led to -04, and the INTDIR
review led to revisions -05 and -06. A further shepherd comment led to -07 (on
the need to include a reference to RFC 2119, and a related section). In the
shepherd’s opinion, the document is ready for IESG review.

(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.
SHEPHERD RESPONSE: As mentioned in the response to question (2), Yasuyuki
Tanaka, Georgios Papadopoulos and Dominique Barthel carried out comprehensive
reviews of the draft. These reviewers have a background in 6TiSCH, where the
topic of the document is of interest.

(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.
SHEPHERD RESPONSE: All document authors have confirmed that they are unaware of
any IPR that applies to this document.

(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR

(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?
SHEPHERD RESPONSE: as mentioned in the response to question (2), the consensus
behind this document is solid, with the WG as a whole understanding and
agreeing 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.)

(11) Identify any ID nits the Document Shepherd has found in this
document. (See and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be
SHEPHERD RESPONSE: There is one "error" (the VRB informational draft, which is
normative for this document) and one comment indicated by the idnits tool. The
relevant details from the idnits tool output follow:

  -- Found something which looks like a code comment -- if you have code
     sections in the document, please surround them with '<CODE BEGINS>' and
     '<CODE ENDS>' lines.
  ** Downref: Normative reference to an Informational draft:
     draft-ietf-lwig-6lowpan-virtual-reassembly (ref. 'LWIG-VRB')
     Summary: 1 error (**), 0 flaws (~~), 0 warnings (==), 1 comment (--).

(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?
SHEPHERD RESPONSE: No: the two normative references that are not yet published
as RFCs (draft-ietf-lwig-6lowpan-virtual-reassembly-01 and
              recovery-07) are ready for advancement.

(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.
SHEPHERD RESPONSE: Yes, draft-ietf-lwig-6lowpan-virtual-reassembly-01 is an
informational document that is included in this document as a normative

(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.
SHEPHERD RESPONSE: This document does not change the status of any existing RFC.

(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 5226).
The document contains 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, etc.
SHEPHERD RESPONSE: Not applicable, as there are no formal language constructs
in the document.