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?

The document requests publication as Best Current Practice. This is indicated in the header.

BCP is appropriate. The document compares the effectiveness of various current techniques of reverse path filtering and presents an additional, enhanced technique.  The current techniques are expressed in RFC2827 and RFC3704, both themselves BCP.  The presented technique is an enhancement of a technique specified in RFC3704.  The document updates RFC3704.

(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 identifies a need for improvement of the unicast
   Reverse Path Filtering techniques (uRPF) (see BCP 84) for detection
   and mitigation of source address spoofing (see BCP 38). The strict
   uRPF technique is inflexible about directionality, the loose uRPF
   technique is oblivious to directionality, and the current
   feasible-path uRPF technique attempts to strike a balance between the
   two (see BCP 84). However, as shown in this draft, the existing
   feasible-path uRPF technique still has shortcomings. This document
   describes an enhanced feasible-path uRPF technique, which aims to be
   more flexible (in a meaningful way) about directionality than the
   feasible-path uRPF technique. It can potentially alleviate ISPs'
   concerns about the possibility of disrupting service for their
   customers, and encourage greater deployment of uRPF techniques..

Working Group Summary

  The document was discussed in grow and in opsec, and adopted by opsec.  Discussions
  in both working groups were incorporated into the document.

Document Quality

Are there existing implementations of the protocol? Have a significant number of vendors indicated their plan to implement the specification? 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? 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? 

The shepherd sees no wg mail indicating that there are are current software implementations.  However, the draft containS a section “Implementation Considerations” that points to the similarity to current uRPF techniques that query a VRF table, so existing implementation methods could be leveraged for this new technique.  One wg comment explicitly said that the document was clear enough to “assist the operators to better implement the recommendations”.  

No MIB Doctor, Media Type, or other expert review was required.


  Who is the Document Shepherd? Who is the Responsible Area

Document Shepherd: Sandra Murphy

Responsible Area Director: Warren Kumari 

(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 document shepherd has reviewed the document, references, and 
the wg discussions and presentations.  The draft was presented and 
discussed in the grow wg, and those interactions were also reviewed.  
The authors have incorporated shepherd comments into the latest version.

(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, there are no document portions that need additional review.

(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.

The shepherd has no concerns or issues with the current version of the

(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.

Yes.  All authors of this document have confirmed on the wg list that they know of no IPR.

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

The shepherd sees no IPR disclosure notice on the wg email list.

(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?   

The wg adoption discussion was energetic.  That discussion appeared to have resolved most issues; the subsequent conversation was not as energetic.  The document as an individual contribution was first discussed in the grow wg.

This draft was presented as an individual submission at grow at IETF97, presented at opsec IETF 99, IETF100, IETF101, and as an opsec draft at IETF104

In total, there were 15 different individuals between the two groups, which is adequately broad support for these groups.

(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.) 

The shepherd sees no threats of appeal in the wg discussions and no indications on the wg list of a discontented wg member.

(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

The nits tool reports:
     Summary: 0 errors (**), 0 flaws (~~), 5 warnings (==), 1 comment (--).

One warning concerns the format of the Updates line in the document header.  The other warnings are about strings in the text that the nits tool thinks are citations, but it appears the tool is just picking up on the use of “[“ in a notation.

(12) Describe how the document meets any required formal review
criteria, such as the MIB Doctor, media type, and URI type reviews.

None required.  There are no features of the draft that require formal review.

(13) Have all references within this document been identified as
either normative or informative?

Yes.  All references are divided into normative and informative sections.

(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?

No.  All IETF documents in the references are RFCs.

(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.

The document header notes that the document will update RFC3704.

(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).

None required.  There are no protocol extensions, no reference to IANA registries, no creation of new IANA registries in this document.

(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.

None required.  There are no new IANA registries created by this document.

(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.

None required.  There are no sections of the document that are XML code, BNF rules, MIM definitions, or any other formal language.