Fast Failover in Protocol Independent Multicast - Sparse Mode (PIM-SM) Using Bidirectional Forwarding Detection (BFD) for Multipoint Networks
draft-ietf-pim-bfd-p2mp-use-case-10

[Ballot comment]
---DISCUSS record---
Hi,

thank you for your work. I have two points I'd like to discuss with you:

1/
You write:
  If the value of the OptionLength field is not equal to 4, the BFD
  Discriminator PIM Hello option is considered malformed, and the
  receiver MUST stop processing PIM Hello options.
Do you mean ignore all other options that would be in the PIM Hello message?
I rapidly skimmed through 7761 and could not find such requirement nor an indication that documents defining new Hello options would have to define how to treat options when at least one is malformed.
It may be that I simply failed to find the relevant text in PIM specs but I'd nevertheless appreciate if you could elaborate a bit on this.

2/
Twice you write that a PIM-SM router MAY/can become a head. First time in 2nd paragraph of 2.1, and the second time in 2.2.
"become" gives a sense of automation, meaning without human intervention, and this is apparently confirmed by section 2.2 where becoming a head is driven by the node becoming a GDR.
The issue I have is that 8562 is pretty explicit about the fact that the transition to Up state for a head is administratively controlled.
You take great care in reusing that word (The head router administratively sets the bfd.SessionState to Up in the MultipointHead session) but I'm not sure this is sufficient to make this an administratively driven action.
Maybe it's simply a discussion about the meaning of "administratively", but according to the understanding I have of this word (which is influenced by the typical use of it in router implementations), it seems to me that this document departs from 8562.

Thank you
---DISCUSS record---

additionally, here are some minor comments:

  it precisely characterizes deployment scenarios for PIM-SM over a LAN
  segment.
What do you mean here? I couldn't find any mention of PIM-SM over a LAN segment in RFC8562.

  HeadDiscriminator: equals the value of My Discriminator
  ([RFC5880]) allocated by the head.
I would specify here that it MUST always be present and MUST NOT be zero.

  The head MUST include the BFD Discriminator option in its Hello
  messages, and it MUST include a 4-byte HeadDiscriminator with a value
  other than zero.
Should this more precisely be written as:
  The head MUST include the BFD Discriminator PIM Hello option in its
  PIM Hello messages, and it MUST include a 4-byte HeadDiscriminator
  with a value other than zero.
If you implement the change I have suggested above then you could remove the second part of the sentence.

  For the tail to
  correctly demultiplex BFD [RFC8562], the source address, and My
  Discriminator values of the BFD packets MUST be the same as those of
  the HeadDiscriminator in the PIM Hello message.
This is not fully clear. Do you mean:
  For the tail to
  correctly demultiplex BFD [RFC8562], the source address and My
  Discriminator of the BFD packets MUST be the same as the source
  address and the HeadDiscriminator, respectively, of the PIM Hello
  message.

s/The document/This document/

[Ballot comment]
This short document looks good to me and thanks for working with it.

I have one comment -

- It would be great to have the "throttling logging mechanism" explained or provide reference for further details. This will help the reader understand better.

[Ballot comment]
The shepherd writeup says simply "Proposed standard" in answer to the question "Why is this the proper type of RFC?".

The SHOULDs in Section 2.1 give the implementer a choice.  I suggest including some guidance about how to make that choice, or perhaps more concretely, when one might opt not to do what the SHOULD says.

[Ballot comment]
I support Martin’s discuss position, and have one other nit. The first sentence in the below is very difficult to parse:

  If a PIM-SM router is configured to monitor the head by using p2mp
  BFD, referred to through this document as 'tail', receives a PIM-
  Hello packet with the BFD Discriminator PIM Hello option, the tail
  MAY create a p2mp BFD session of type MultipointTail, as defined in
  [RFC8562].

Suggested rewrite: “A PIM-SM router that is configured to monitor the head by using p2mp BFD is referred to throughout this document as a “tail”. When such a tail receives a PIM-Hello…”

[Ballot comment]
Thank you for the work put into this document.

Please find below some non-blocking COMMENT points (but replies would be appreciated even if only for my own education).

Special thanks to Mike McBride the shepherd's write-up including the section about the WG consensus.

I hope that this helps to improve the document,

Regards,

-éric

== COMMENTS ==

Does the use of BFD prevent the use of normal PIM detection? It is a little unclear from the text and I hope that BFD comes on the top of normal PIM detection mode.

-- Section 2.3 --
Please add "All received BFD Control packets that are
  demultiplexed to the session MUST be discarded if the received TTL or
  Hop Limit is not equal to 255." Copied from RFC 5881.

-- Section 4 --
The security section appears rather light to me as now any BFD security issues can also impact PIM.

Closed request for Telechat review by INTDIR with state 'Withdrawn': The document is on the IESG telechat in 2 days (deadline was today). No need anymore for a review (still welcome by the authors probably).

[Ballot comment]
Thanks to Meral Shirazipour for their General Area Review Team (Gen-ART) review
(https://mailarchive.ietf.org/arch/msg/gen-art/3VY7s4HnPhPf8ijxLhhh9gHNp10).

-------------------------------------------------------------------------------
All comments below are about very minor potential issues that you may choose to
address in some way - or ignore - as you see fit. Some were flagged by
automated tools (via https://github.com/larseggert/ietf-reviewtool), so there
will likely be some false positives. There is no need to let me know what you
did with these suggestions.

Section 2.1. , paragraph 5, nit:
> affecting the PIM state in any way. Thus the tail stops using BFD to monitor
>                                    ^^^^
A comma may be missing after the conjunctive/linking adverb "Thus".

[Ballot comment]
Hi,

I was surprised by both of the statements in section 2.3 (but that may just be due to my lack of BFD expertise):

1. Wouldn't the base BFD protocol specify the TTL or Hop Limit?  Or is there a special/different consideration when BFD is being used for this use case that justifies RFC 2119 language?

2. This may just be my lack of BFD knowledge because I had assumed that BFD sessions could be shared between different protocols wanting fast failure detection, and hence I was surprised that the p2mp BFD session MUST be targeted to the ALL-PIM-ROUTERs multicast address?

Thanks,
Rob

[Ballot comment]
Hi,

I was surprised by both of the statements in section 2.3 (but that may just be due to my lack of BFD expertise):

1. Wouldn't the base BFD protocol specify the TTL or Hop Limit?  Or is there a special/different consideration when BFD is being used for this use case?

2. This may just be my lack of BFD knowledge because I had assumed that BFD sessions could be shared between different protocols wanting fast failure detection, and hence I was surprised that the p2mp BFD session MUST be targeted to the ALL-PIM-ROUTERs multicast address?

Thanks,
Rob

[Ballot comment]
Do we want to provide any guidance on how to configure the BFD
parameters (most notably the timeout intervals)?  (I assume the answer
is "no", but still have to ask.)

Section 1

  Among specific characteristics of p2mp BFD that particularly benefit
  PIM-SM over a LAN segment is a faster transition to the Up state of
  the p2mp BFD session due to avoidance of the three-way handshake
  required in p2p BFD [RFC5880].  [...]

I'm not sure I understand how this works.  RFC 8562 seems to require the
head node to stay in down state for the max timeout before transitioning
to "up" and starting to send control packets.  With a three-way
handshake there is immediate feedback at startup and, while there is a
round-trip cost incurred, there is no mandatory enforced delay.  Could
you say a bit more about which scenarios are being compared so that p2mp
BFD is faster to Up than p2p BFD?

                                                        Point-to-
  multipoint (p2mp) BFD can enable faster detection of PIM-SM router
  failure and thus minimize multicast service disruption.  [...]

Just to confirm: here, the comparison is PIM-SM without BFD against
PIM-SM with (p2mp) BFD, right?  So that we're going from 105 seconds to
potentially sub-second detection.  Assuming that, I'd consider "faster
detection of PIM-SM router failure compared to PIM-SM without BFD".

Section 2.1

  Note that any PIM-SM router, regardless of its role, MAY become a
  head of a p2mp BFD session.  [...]

While I don't see any problem with this behavior, I'm also a bit
confused as to when an arbitrary (i.e., non-RP) router would benefit
from being the head of a p2mp BFD session.  Also, RFC 7761 doesn't seem
to use "role" as a defined term, so there may be some room for
clarification if we had particular roles in mind.

  If a PIM-SM router is configured to monitor the head by using p2mp
  BFD, referred to through this document as 'tail', receives a PIM-
  Hello packet with the BFD Discriminator PIM Hello option, the tail

Since we're presuming that the tail is configured to monitor "the head",
does this behavior only apply to PIM-Hello packets received specifically
from "the head" (as opposed to all received PIM-Hello packets)?

  If the tail detects a MultipointHead failure [RFC8562], it MUST
  delete the corresponding neighbor state and follow procedures defined
  in [RFC7761].

Do we want to give a more precise reference for which RFC 7761
procedures are to be followed in this case?  (Perhaps, the
neighbor.timeout behavior?)  (Also, we might clarify that the neighbor
state being deleted is the PIM state, not the BFD state.)

Section 2.2

                The head router administratively sets the
  bfd.SessionState to Up in the MultipointHead session [RFC8562] only
  if it is a Group Designated Router (GDR) Candidate, as specified in
  Sections 5.5 and 5.6 of [RFC8775].  If the router is no longer the
  GDR, then it MUST shut down following the procedures described in
  Section 5.9 [RFC8562].  [...]

There seems to be a slight mismatch, here -- we start the BFD session if
we're a GDR *Candidate*, and stop it if we're no longer *the GDR*.  So
what do we do if we are a candidate but not the selected GDR?

                          For each GDR Candidate that includes BFD
  Discriminator option in its PIM Hello, the PIM DR creates a
  MultipointTail session [RFC8562].  [...]

Interestingly, this seems to be a stronger requirement on the tail than
in the non-RFC8775 case, where we just say "MAY create a p2mp BFD
session of type MultipointTail".  It might be worth emphasizing the
contrast by using "MUST" here (assuming that the contrast is intended).

            If PIM DR detects a failure of one of the sessions, it MUST
  remove that router from the GDR Candidate list and immediately
  transmit a new DRLB-List option.

Is this "MUST ... immediately transmit" going to run any risk of causing
a traffic spike/congestion?  I find it unlikely, but am not really an
expert here.

Section 2.3

  The MultipointHead of a p2mp BFD session when transmitting BFD
  Control packets:

      MUST set TTL or Hop Limit value to 255 (Section 5 [RFC5881]);

Is there a corresponding requirement or recommendation on tails to
reject BFD Control packets with received TTL or Hop Limit not equal to
255?  Where is this requirement specified?

Section 4

  The security considerations discussed in [RFC7761], [RFC5880],
  [RFC8562], and [RFC8775] apply to this document.

Do the considerations of RFC 5881 also apply?

NITS

Section 1

  Bidirectional Forwarding Detection (BFD) [RFC5880] had been
  originally defined to detect a failure of a point-to-point (p2p)

I'd s/had been/was/ -- the "had been" verb tense feels out of place
here.

[Ballot discuss]
Hi,

thank you for your work. I have two points I'd like to discuss with you:

1/
You write:
  If the value of the OptionLength field is not equal to 4, the BFD
  Discriminator PIM Hello option is considered malformed, and the
  receiver MUST stop processing PIM Hello options.
Do you mean ignore all other options that would be in the PIM Hello message?
I rapidly skimmed through 7761 and could not find such requirement nor an indication that documents defining new Hello options would have to define how to treat options when at least one is malformed.
It may be that I simply failed to find the relevant text in PIM specs but I'd nevertheless appreciate if you could elaborate a bit on this.

2/
Twice you write that a PIM-SM router MAY/can become a head. First time in 2nd paragraph of 2.1, and the second time in 2.2.
"become" gives a sense of automation, meaning without human intervention, and this is apparently confirmed by section 2.2 where becoming a head is driven by the node becoming a GDR.
The issue I have is that 8562 is pretty explicit about the fact that the transition to Up state for a head is administratively controlled.
You take great care in reusing that word (The head router administratively sets the bfd.SessionState to Up in the MultipointHead session) but I'm not sure this is sufficient to make this an administratively driven action.
Maybe it's simply a discussion about the meaning of "administratively", but according to the understanding I have of this word (which is influenced by the typical use of it in router implementations), it seems to me that this document departs from 8562.

Thank you

[Ballot comment]
additionally, here are some minor comments:

  it precisely characterizes deployment scenarios for PIM-SM over a LAN
  segment.
What do you mean here? I couldn't find any mention of PIM-SM over a LAN segment in RFC8562.

  HeadDiscriminator: equals the value of My Discriminator
  ([RFC5880]) allocated by the head.
I would specify here that it MUST always be present and MUST NOT be zero.

  The head MUST include the BFD Discriminator option in its Hello
  messages, and it MUST include a 4-byte HeadDiscriminator with a value
  other than zero.
Should this more precisely be written as:
  The head MUST include the BFD Discriminator PIM Hello option in its
  PIM Hello messages, and it MUST include a 4-byte HeadDiscriminator
  with a value other than zero.
If you implement the change I have suggested above then you could remove the second part of the sentence.

  For the tail to
  correctly demultiplex BFD [RFC8562], the source address, and My
  Discriminator values of the BFD packets MUST be the same as those of
  the HeadDiscriminator in the PIM Hello message.
This is not fully clear. Do you mean:
  For the tail to
  correctly demultiplex BFD [RFC8562], the source address and My
  Discriminator of the BFD packets MUST be the same as the source
  address and the HeadDiscriminator, respectively, of the PIM Hello
  message.

s/The document/This document/

(Via drafts-lastcall@iana.org): IESG/Authors/WG Chairs:

The IANA Functions Operator has completed its review of draft-ietf-pim-bfd-p2mp-use-case-08. If any part of this review is inaccurate, please let us know.

The IANA Functions Operator understands that, upon approval of this document, there is a single action which we must complete.

In the PIM-Hello Options registry on the Protocol Independent Multicast (PIM) Parameters registry page located at:

https://www.iana.org/assignments/pim-parameters/

a new option is to be registered as follows:

Value: [ TBD-at-Registration ]
Length: 4
Name: BFD Discriminator Option
Reference: [ RFC-to-be ]

As this document requests registrations in a Specification Required (see RFC 8126) registry, we will initiate the required Expert Review via a separate request. This review must be completed before the document's IANA state can be changed to "IANA OK."

The IANA Functions Operator understands that this is the only action required to be completed upon approval of this document.

Note:  The actions requested in this document will not be completed until the document has been approved for publication as an RFC. This message is meant only to confirm the list of actions that will be performed.

Thank you,

Sabrina Tanamal
Lead IANA Services Specialist

The following Last Call announcement was sent out (ends 2021-09-28):

From: The IESG
To: IETF-Announce
CC: aretana.ietf@gmail.com, draft-ietf-pim-bfd-p2mp-use-case@ietf.org, mmcbride7@gmail.com, pim-chairs@ietf.org, pim@ietf.org
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (Fast Failover in Protocol Independent Multicast - Sparse Mode (PIM-SM) Using Bidirectional Forwarding Detection (BFD) for Multipoint Networks) to Proposed Standard


The IESG has received a request from the Protocols for IP Multicast WG (pim)
to consider the following document: - 'Fast Failover in Protocol Independent
Multicast - Sparse Mode (PIM-SM)
  Using Bidirectional Forwarding Detection (BFD) for Multipoint
  Networks'
  as Proposed Standard

The IESG plans to make a decision in the next few weeks, and solicits final
comments on this action. Please send substantive comments to the
last-call@ietf.org mailing lists by 2021-09-28. Exceptionally, comments may
be sent to iesg@ietf.org instead. In either case, please retain the beginning
of the Subject line to allow automated sorting.

Abstract


  This document specifies how Bidirectional Forwarding Detection for
  multipoint networks can provide sub-second failover for routers that
  participate in Protocol Independent Multicast - Sparse Mode (PIM-SM).
  An extension to the PIM Hello message used to bootstrap a point-to-
  multipoint BFD session is also defined in this document.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-pim-bfd-p2mp-use-case/


The following IPR Declarations may be related to this I-D:

  https://datatracker.ietf.org/ipr/4172/
  https://datatracker.ietf.org/ipr/3302/

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

(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 discusses the use of Bidirectional Forwarding Detection
(BFD) for multi-point networks to provide nodes that participate in
Protocol Independent Multicast - Sparse Mode (PIM-SM) with sub-
second convergence. An optional extension to PIM-SM Hello, as specified
in RFC 7761, to bootstrap a point-to-multipoint BFD session, is also
defined in this document.

Working Group Summary:

The draft was developed for over 2 years and when it came time for WGLC we had full consensus.

Document Quality:

There was thorough review by individuals representing multiple vendors. But there are no implementations currently.

Personnel:

Who is the Document Shepherd?
Mike McBride

Who is the Responsible Area Director?
Alvaro Retana

(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.

There are a few nit areas, to improve readability, that the authors will fix and submit in a new version. Otherwise it's ready for publication.

(4) Does the document Shepherd have any concerns about the depth or breadth of the reviews that have been performed?

No concerns

(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

(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.

No concerns

(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. IPR has been disclosed by authors.

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

No problem as a WG with IPR disclosure.

(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?

Solid support from multiple vendors and service providers.

(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.

(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.

I identified nits in the sentence structure of the Abstract which the authors will fix. ID Nits is AOK.

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

No formal review requested or needed.

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

Yes.

(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 are two normative references that are progressing and should be ready for advancement soon.

(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.

No.

(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.

(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).

IANA registry has been clearly identified. This draft allocates a new OptionType value from the PIM Hello Options 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.

N/A

(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.

N/A

(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?

N/A

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

(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 discusses the use of Bidirectional Forwarding Detection
(BFD) for multi-point networks to provide nodes that participate in
Protocol Independent Multicast - Sparse Mode (PIM-SM) with sub-
second convergence. An optional extension to PIM-SM Hello, as specified
in RFC 7761, to bootstrap a point-to-multipoint BFD session, is also
defined in this document.

Working Group Summary:

The draft was developed for over 2 years and when it came time for WGLC we had full consensus.

Document Quality:

There was thorough review by individuals representing multiple vendors. But there are no implementations currently.

Personnel:

Who is the Document Shepherd?
Mike McBride

Who is the Responsible Area Director?
Alvaro Retana

(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.

There are a few nit areas, to improve readability, that the authors will fix and submit in a new version. Otherwise it's ready for publication.

(4) Does the document Shepherd have any concerns about the depth or breadth of the reviews that have been performed?

No concerns

(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

(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.

No concerns

(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. IPR has been disclosed by authors.

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

No problem as a WG with IPR disclosure.

(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?

Solid support from multiple vendors and service providers.

(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.

(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.

I identified nits in the sentence structure of the Abstract which the authors will fix. ID Nits is AOK.

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

No formal review requested or needed.

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

Yes.

(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 are two normative references that are progressing and should be ready for advancement soon.

(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.

No.

(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.

(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).

IANA registry has been clearly identified. This draft allocates a new OptionType value from the PIM Hello Options 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.

N/A

(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.

N/A

(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?

N/A

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

(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 discusses the use of Bidirectional Forwarding Detection
(BFD) for multi-point networks to provide nodes that participate in
Protocol Independent Multicast - Sparse Mode (PIM-SM) with sub-
second convergence. An optional extension to PIM-SM Hello, as specified
in RFC 7761, to bootstrap a point-to-multipoint BFD session, is also
defined in this document.

Working Group Summary:

The draft was developed for over 2 years and when it came time for WGLC we had full consensus.

Document Quality:

There was thorough review by individuals representing multiple vendors. But there are no implementations currently.

Personnel:

Who is the Document Shepherd?
Mike McBride

Who is the Responsible Area Director?
Alvaro Retana

(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.

There are a few nit areas, to improve readability, that the authors will fix and submit in a new version. Otherwise it's ready for publication.

(4) Does the document Shepherd have any concerns about the depth or breadth of the reviews that have been performed?

No concerns

(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

(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.

No concerns

(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. IPR has been disclosed by authors.

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

No problem as a WG with IPR disclosure.

(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?

Solid support from multiple vendors and service providers.

(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.

(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.

I identified nits in the sentence structure of the Abstract which the authors will fix. ID Nits is AOK.

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

No formal review requested or needed.

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

Yes.

(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 are two normative references that are progressing and should be ready for advancement soon.

(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.

No.

(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.

(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).

IANA registry has been clearly identified. This draft allocates a new OptionType value from the PIM Hello Options 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.

N/A

(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.

N/A

(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?

N/A