OSPF Bidirectional Forwarding Detection (BFD) Strict-Mode
draft-ietf-lsr-ospf-bfd-strict-mode-10

[Ballot comment]
Thanks for this document.  I think that what is being proposed here is useful.

A few minor/nit comments that may improve this document.

Minor level comments:

(1) p 6, sec 5.  Operations & Management Considerations

Not for this document, and ss per my other OSPF ballots, I assume that the LSR WG will update the OSPF YANG model will be updated to accommodate this feature.


(2) p 6, sec 5.  Operations & Management Considerations

  In network deployments with noisy or degraded links with intermittent
  packet loss, BFD sessions may flap resulting in OSPF adjacency flaps.
  This in turn may cause routing churn.  The use of OSPF BFD strict-
  mode along with mechanisms such as hold-down (a delay in the initial
  OSPF adjacency bringup following BFD session establishment) and/or
  dampening (a delay in the OSPF adjacency bringup following failure
  detected by BFD) may help reduce the frequency of adjacency flaps and
  therefore reduce the associated routing churn.  The details of these
  mechanisms are outside the scope of this document.

For my understanding, is the expectation that if a device supports this feature then it would (or is that SHOULD) be enabled automatically?



Nit level comments:

(3) p 6, sec 6.  Backward Compatibility

  established successfully.  Implementations MAY provide a local
  configuration option to enable BFD without the strict-mode which
  results in the router not advertising the B-bit and BFD operation
  being performed in the same way as prior to this specification.

I find the text about enable BFD without the strict-mode to be slightly unclear, since presumably it is the OSPF interactions with BFD that the configuration is referred to, rather than BFD itself.  Perhaps changing "strict-mode" to "OSPF BFD strict-mode" might be clearer.

[Ballot comment]
Thank you for this document.

When I started reading this document / read the Abstract, I must admit I thought "This is a silly idea, and smacks of creeping featuritis and premature optimization. This is an already solved problem - you bring up OSPF and *then* use that to signal that you want BFD...."
and then I actually read the Introduction section and the use-case / utility became clear...

My only question (and I'm suspecting it has already been discussed) if is there should actually be some (small) delay after the BFD session establishment to allow the interface to "settle" / give BFD a second or two to figure out if the link is actually "stable" - having BFD come up and then immediately bringing up the adjacency, only to have BFD pull it down 10ms later doesn't seem to solve the issue really... unless it is expected that the OSPF exchange is sufficiently slow that BFD would detect it before OSPF is actually working?

[Ballot comment]

# Éric Vyncke, INT AD, comments for draft-ietf-lsr-ospf-bfd-strict-mode-09
CC @evyncke

Thank you for the work put into this document. It is short, clear, and useful (hence my YES).

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

Special thanks to Acee Lindem for the shepherd's detailed write-up including the WG consensus and the justification of the intended status.

I hope that this review helps to improve the document,

Regards,

-éric

## COMMENTS

### Section 3

Suggest to move section 3 (Local Interface IPv4 Address TLV) as a subsection of section 4.1 (OSPFv3 IPv4 Address-Family Specifics) as, at least for me, the reader cannot understand the use of section 3 before reading section 4.1

As I am not an OSPFv3 expert, the following question is possibly irrelevant, but can the IPv4 address be a link-local (i.e., 169.254/16)?

### Section 4.1

```
  ... In most deployments of
  OSPFv3 IPv4 AF, it is required that BFD is used to monitor and verify
  IPv4 data plane connectivity between the routers on the link and,
  hence, the BFD session is setup using IPv4 neighbor addresses.
```

The text is a little unclear whether an IPv6 BFD session is also required.

## Notes

This review is in the ["IETF Comments" Markdown format][ICMF], You can use the
[`ietf-comments` tool][ICT] to automatically convert this review into
individual GitHub issues.

[ICMF]: https://github.com/mnot/ietf-comments/blob/main/format.md
[ICT]: https://github.com/mnot/ietf-comments

[Ballot comment]
Thank you to Wes Hardaker for the SECDIR review.

** Section 1.  Typo. s/adjaceny/adjacency/

** Section 1.  Typo. s/establishement/establishment/

** Section 8. 
  If
  authentication is being used in the OSPF routing domain
  [RFC5709][RFC7474], then the Cryptographic Authentication TLV
  [RFC5613] SHOULD also be used to protect the contents of the LLS
  block.

Since strict-mode BFD functionality is not going to be present in legacy implementations, could it be mandatory to protect the LLS block (i.e., use of the Cryptographic Authentication TLV is a MUST)?

[Ballot comment]
# GEN AD review of draft-ietf-lsr-ospf-bfd-strict-mode-08

CC @larseggert

Thanks to Russ Housley for the General Area Review Team (Gen-ART) review
(https://mailarchive.ietf.org/arch/msg/gen-art/xOoiX0uoXF7M46B5LDSy2kfnPlM).

## Nits

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.

### Typos

#### Section 1, paragraph 2
```
-    enable fast routing convergence.  OSPF adjaceny flaps may occur over
+    enable fast routing convergence.  OSPF adjacency flaps may occur over
+                                                  +
```

#### Section 1, paragraph 3
```
-    establishement as described in section 4.1 of [RFC5882].
-            -
```

## Notes

This review is in the ["IETF Comments" Markdown format][ICMF], You can use the
[`ietf-comments` tool][ICT] to automatically convert this review into
individual GitHub issues. Review generated by the [`ietf-reviewtool`][IRT].

[ICMF]: https://github.com/mnot/ietf-comments/blob/main/format.md
[ICT]: https://github.com/mnot/ietf-comments
[IRT]: https://github.com/larseggert/ietf-reviewtool

It looks like there are some agreed changes to reflect IETF LC/directorate review comments? Let’s get a new version posted for those, and then we can schedule this on the next IESG agenda.

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

The IANA Functions Operator has completed its review of draft-ietf-lsr-ospf-bfd-strict-mode-07. If any part of this review is inaccurate, please let us know.

The IANA Services Operator understands that, upon approval of this document, there are two actions which we must complete.

First, in the LLS Type 1 Extended Options and Flags registry on the Open Shortest Path First (OSPF) Link Local Signalling (LLS) - Type/Length/Value Identifiers (TLV) registry page located at:

https://www.iana.org/assignments/ospf-lls-tlvs/

the temporary registration for LLS Type 21:

LLS Type: 21
Name: Local Interface IPv4 Address TLV

will be made permanent and have its reference changed to [ RFC-to-be ].

Second, in the LLS Type 1 Extended Options and Flags registry also on the Open Shortest Path First (OSPF) Link Local Signalling (LLS) - Type/Length/Value Identifiers (TLV) registry page located at:

https://www.iana.org/assignments/ospf-lls-tlvs/

the existing registration for Extended Options Bit 0x00000010:

Extended Options Bit: 0x00000010
Name: B-bit

will have its reference changed to [ RFC-to-be ].

The IANA Services Operator understands that these two actions are the only ones 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.

For definitions of IANA review states, please see:

https://datatracker.ietf.org/help/state/draft/iana-review

Thank you,

Sabrina Tanamal
Lead IANA Services Specialist

The following Last Call announcement was sent out (ends 2022-09-20):

From: The IESG
To: IETF-Announce
CC: acee@cisco.com, draft-ietf-lsr-ospf-bfd-strict-mode@ietf.org, jgs@juniper.net, lsr-chairs@ietf.org, lsr@ietf.org
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (OSPF BFD Strict-Mode) to Proposed Standard


The IESG has received a request from the Link State Routing WG (lsr) to
consider the following document: - 'OSPF BFD Strict-Mode'
  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 2022-09-20. 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 the extensions to OSPF that enable an OSPF
  router to signal the requirement for a Bidirectional Forwarding
  Detection (BFD) session prior to adjacency formation.  Link-Local
  Signaling (LLS) is used to advertise the requirement for strict-mode
  BFD session establishment for an OSPF adjacency.  If both OSPF
  neighbors advertise BFD strict-mode, adjacency formation will be
  blocked until a BFD session has been successfully established.

  This document updates RFC2328 by augmenting the OSPF neighbor state
  machine with a check for BFD session up before progression from Init
  to Two-Way state when operating in OSPF BFD strict-mode.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-lsr-ospf-bfd-strict-mode/



No IPR declarations have been submitted directly on this I-D.

(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 Proposed Standard.

Proposed standard - The document is proposed standard since it specifies protocol encoding modifications, as well as, extensions to the OSPF neighbor FSM.

(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 provides extensions to OSPF to require a BFD session (i.e., strict-mode) prior to OSPF adjacency formation. Extensions are provided both OSPF Link-Local-Signaling to advertise the desire to require a BFD session and to the OSPF neighbor FSM should BFD strict-mode be successfully negotiated.

Working Group Summary:

There is stong support among those reviewing the document. The WG last call of the document prompted discussions of additional specification. There was debate regarding making the delay timer described in section 5 a normative requirement. The consensus was to not make this a normative part of the specification. I feel this is the right decision – especially given that this is new functionality being requested at Working Group Last Call and implementations accomplish the dampening in varying ways.


Document Quality:

The document is of high quality and has been reviewed by several LSR WG members. This same function is already standardized for IS-IS [RFC6213]

Personnel:

Document Shepherd: Acee Lindem
Responsible AD: John Scudder

(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 reviewed the document multiple times and provided editorial comments. The shepherd's reviews are acknowledged in the draft.

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

No. A Routing Director review was provided and all comments were addressed.

https://datatracker.ietf.org/doc/review-ietf-lsr-ospf-bfd-strict-mode-04-rtgdir-lc-smith-2022-02-01/

(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.

None.

(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.

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

No.

(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?

There is strong support for publication and minimal objection.

(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.

No nits.

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

None of these are applicable. The YANG model augmentations will be added in a separate draft.

(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?

No.

(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).

This document has IANA registrations and these have been reviewed by the WG and assigned through the early allocation process.

(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.

The OSPF allocations of the TLV and Capability B come from existing 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.

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

(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 Proposed Standard.

Proposed standard - The document is proposed standard since it specifies protocol encoding modifications, as well as, extensions to the OSPF neighbor FSM.

(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 provides extensions to OSPF to require a BFD session (i.e., strict-mode) prior to OSPF adjacency formation. Extensions are provided both OSPF Link-Local-Signaling to advertise the desire to require a BFD session and to the OSPF neighbor FSM should BFD strict-mode be successfully negotiated.

Working Group Summary:

There is stong support among those reviewing the document. The WG last call of the document prompted discussions of additional specification. There was debate regarding making the delay timer described in section 5 a normative requirement. The consensus was to not make this a normative part of the specification. I feel this is the right decision – especially given that this is new functionality being requested at Working Group Last Call and implementations accomplish the dampening in varying ways.


Document Quality:

The document is of high quality and has been reviewed by several LSR WG members. This same function is already standardized for IS-IS [RFC6213]

Personnel:

Document Shepherd: Acee Lindem
Responsible AD: John Scudder

(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 reviewed the document multiple times and provided editorial comments. The shepherd's reviews are acknowledged in the draft.

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

No. A Routing Director review was provided and all comments were addressed.

https://datatracker.ietf.org/doc/review-ietf-lsr-ospf-bfd-strict-mode-04-rtgdir-lc-smith-2022-02-01/

(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.

None.

(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.

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

No.

(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?

There is strong support for publication and minimal objection.

(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.

No nits.

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

None of these are applicable. The YANG model augmentations will be added in a separate draft.

(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?

No.

(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).

This document has IANA registrations and these have been reviewed by the WG and assigned through the early allocation process.

(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.

The OSPF allocations of the TLV and Capability B come from existing 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.

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