Shepherd writeup

Update on March 5th 2018 for draft-ietf-bfd-multipoint-active-tail-07: all the comments have been addressed as discussed on the BFD WG alias.

draft-ietf-bfd-multipoint-active-tail-06 shepherd write-up.

: 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)?  
Standards Track as indicated in title pager header.

: Why is this the proper type of RFC?  
It is a normative reference in draft-ietf-trill-p2mp-bfd

: Is this type of RFC indicated in the title page 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:

: Technical Summary
This document describes active tail extensions to the Bidirectional
Forwarding Detection (BFD) protocol for multipoint and multicast

: Working Group Summary
The document was discussed multiple times with participation from multiple members of the BFD WG. The discussions on whether a separate draft (v/s move to appendix) was needed for active-tail went on for a while but consensus was reached. Most of the technical discussions took place in 2014/2015 when the active-tail functionality was still part of the multipoint draft (i.e. before the split). The technical discussions were mostly on the notification mechanisms to the head, whether they are all needed and how the operate.

: Document Quality
The document has been reviewed multiple times on the BFD WG mailing list. 
There is no known implementation of this draft. Huawei may implement draft-ietf-trill-p2mp-bfd (, if they do they will need to also implement this draft.

: Personnel
:   Who is the Document Shepherd? 
Reshad Rahman is the document shepherd, BFD WG co-chair.
: Who is the Responsible Area Director?
Alvaro Retana 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.
The shepherd has gone though all the email discussions on the BFD WG mail archive and has verified that the issues raised have been addressed appropriately from a technical view.
The document will need a new version before being forwarded to the IESG.

: (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.

: (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 believes that the document is not ready for publication yet (but close), there are a few nits to be fixed (see below).

: (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.
Waiting for response from some authors.

: (8) Has an IPR disclosure been filed that references this document?
: If so, summarize any WG discussion and conclusion regarding the IPR
: disclosures.
Waiting for response from some authors.

: (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?   
Consensus is very solid.

: (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
: thorough.
1 warning about a later version (-12) exists of draft-ietf-bfd-multipoint-11
1 comment about the document date being 30 days in the past.

: (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 will update RFCs 5880 and 7880. They are not in the title page header.

: (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).
There are no protocol extensions which require a registry. 

: (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.


- General. There are a few instances where singular is used instead of plural (e.g. for session, tail) and also where “a” or “the” is missing. I have tried to indicate all such occurrences below.
- General. A few sentences have the period ‘.’ before the closing parenthesis instead of after, e.g. in Introduction “path as is feasible.)”. I have not called out all of them, search for “.)”
- 1 Introduction. s/which allows tail/which allows tails/
- 1 Introduction. Clarifications/explanations are desirable on “it is preferable if unicast paths share as little fate with the multipoint path as is feasible.)”
- 1 Introduction. s/Goal of this application/The goal of this application/
- 1 Introduction mentions “…state implosion towards the head”. Not sure implosion is the right term there, if it is the right term then clarification is needed.
- 2 Overview. Change “Head may wish” to “A head may wish” or “Heads may wish”
- 2 Overview. “…the head can direct the tails to transmit…”: add reference or explanation on how the head does that. Also s/direct/request/?
- 2 Overview. 1st paragraph, I know it’s obvious when you read the draft but might be good to have 1 sentence to explain why this is unreliable.
- 2 Overview. 3rd paragraph: s/as a unicast to the tail/as a unicast to that tail/?
- 2 Overview. 3rd paragraph: “or the single reply thereto is lost”, rephrase that sentence e.g. to “or the single reply os also lost”?
- 2 Overview. “If some tails are more equal than others…”. I know what you mean but plus change the wording.
- 3 Protocol Details. s/This section is update/This section is an update/
- 3.2 Multipoint Client Session Failure. s/know the tail state/know the tail’s state/
- 3.3 State Variables. As discussed, bfd.SessionType should be in “new variable values” section and the others in “new variables” section.
- 3.3.1 New State Variables. The paragraph on bfd.ReportTailDown says “If 0, the tail..”. Mention that the packets sent from the tail are in response to the head’s periodic BFD control packets? Also when set to 1, how do the tails know from the head that they need to notify the head? This paragraph needs some clarification.
3.3.2 State Variable Initialization and Maintenance. s/section 6.8.1 of the [RFC5880] needs/section 6.8.1 of [RFC5880] need/
- 3.4 Controlling Multipoint BFD Options. 2nd paragraph: add reference to section 5.1?
- 3.4. 3rd paragraph : add reference to section 5.3? Also do we need a state variable which controls this behaviour (discovering tails)?
- 3.4. Paragraph 5 should be after paragraph 3?
- 3.4. Paragraph 6, regarding “initial delay”, add a reference to 3.13.3 which describes the delay.
- 3.5 State Machine. s/State machine for/The state machine for/
- 3.8 Soliciting the Tails. “random delay”, add a reference to 3.13.3 which describes the delay.
- 3.13. “in the base specification” refers to base BFD or base BFD multipoint? Add a reference.
- 3.13.1. Should reception at head also be covered here? If not, add “at tail” to the title
- 3.13.1. s/by head below procedure MUST be/by the head, the procedure below MUST be/
- 3.13.1 and 3.13.2. Both are adding to the procedures in draft-ietf-bfd-multipoint, specify where the addition is taking place (e.g. at the end).
- 7 Security Considerations. Should we add at the beginning “The same security considerations as those described in [RFC5880] and [I-D.ietf-bfd-multipoint] apply to this document.”?