Shepherd writeup

Update July 23rd 2020. Comments on draft-ietf-bfd-stability-06

General: NULL authentication TLV is still used, should be replaced with NULL authentication type or section as appropriate.
Be consistent for Null v/s NULL (NULL Auth is used in bfd-optimizing-authentication)
s/detect lost packet/detect lost packets/
Section 3 Use Cases:
s/any BFD packet loss if loss/any BFD packet loss if the loss/
s/BFD implementation/BFD implementations/
Where the text says “failure of a link”, might be better to say “failure of a datapath”?
Informative references to CFM and TWAMP would be useful
Section 4
“by appending the Null-Authentication type “. Suggest “by appending an authentication section with the NULL Authentication type “
Section 5
“BFD uses authentication TLV”, suggest change to “BFD uses an authentication section”.
“BFD packets MUST include NULL-Auth TLV”. Change to “BFD control packets MUST include an authentication section with the NULL Authentication type”
Section 5.1
“The first BFD NULL-Auth type processed by the receiver…”.  Change to  “The first BFD authentication section with the NULL Authentication type, in a valid BFD control packet, processed by the receiver” .
Also, does it have to be NULL Auth, I believe it can be any auth with sequence number? If that’s the case change to  “The first BFD authentication section with a non-zero sequence number, in a valid BFD control packet, processed by the receiver is used for….”.

(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? 
Standards Track as indicated on title page.

(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 extensions to the Bidirectional Forwarding
Detection (BFD) protocol to measure BFD stability.  Specifically, it
describes a mechanism for detection of BFD control packet loss.

Relevant content can frequently be found in the abstract and/or introduction of the document. If not, this may be an indication that there are deficiencies in the abstract or introduction. 

Working Group Summary:
There have been many discussions since 2014 on this document. The document has been improved and simplified based on feedback+discussions, e.g. timestamps was removed.

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 rough? 

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, YANG 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 document is well-written, concise and technically accurate, but requires some editorial changes before being forwarded to the IESG. 


Who is the Document Shepherd? 
Reshad Rahman, BFD co-chair.

Who is the Responsible Area Director? 
Martin Vigoureux 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 through the document, email archive and meeting minutes. Comments have been addressed.

(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. 

(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?

(8) Has an IPR disclosure been filed that references this document? If so, summarize any WG discussion and conclusion regarding the IPR disclosures. 
No 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? 
WG consensus is 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 comment regarding document date being 106 days in the past.

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

(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). 

(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, YANG modules, etc.

(20) If the document contains a YANG module, has the module been checked with any of the recommended validation 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?


-	Don’t use NULL-authentication TLV, use RFC5880 language. e.g.NULL-authentication type.
-	s/control frame/control packet/ (reuse same terms as in RFC5880)
-	CC frames is not defined in BFD, use “control packets” instead?
-	Terminology section would help. In there: secure sequence numbers, meticulous authentication etc could be added.
-	Missing “the”, “an” in a few sentences. 


Following sentence is long and not super clear, what’s the essence of the point it’s trying to make?
I’m having a hard time digesting “…, the tolerance for lost or delayed frames in the Detection Time,”. Is it just saying that Detection Time is usually set to smallest value and 
because of this there’s little tolerance for delayed/lost packets? Needs tweaking.

                                                      .In order to
   prevent significant data loss due to a datapath failure, the
   tolerance for lost or delayed frames in the Detection Time, as
   defined in BFD [RFC5880] is set to the smallest feasible value.

s/does not propose BFD extension/does not propose any BFD extension/

Requirements Language
Please put this is a separate (sub)section later in the doc, e.g. after intro. Add RFC8174, and have RFCs 2119 and 8174  as normative references.

2. Use cases

Legacy BFD? Why not say BFD as specified in RFC5880. Or add “Legacy BFD”  in terminology section.

Instead of “dead interval”, use “Detection Time” as defined in RFC5880.
s/This draft/This document/
s/enables BFD engine/enables the BFD engine/
Instead of “BFD engine”, use “BFD implementation”? I understand what you mean by “BFD engine”, and ok if you keep it, but it’s not a term I’ve seen in BFD drafts/RFCs.

s/In a faulty datapath scenario, operator/In a faulty datapath scenario, an operator/
Add references for CFM and TWAMP in last paragraph?

3.  BFD Null-Authentication TLV

Rename to BFD Null-Authentication section?
s/BFD control frame that do not/BFD control packets that do not/

Suggestion: consider putting this is a sub-section of section 4 “Theory of operation”?

4. Theory of operations

s/4. Theory of operations/4. Theory of operation/

s/This mechanism allows operator/This mechanism allows operators/


Following needs clarification. What is “appropriately recorded”? For secure sequence number, add normative reference to draft-ietf-bfd-secure-sequence-numbers.

   When using
   secure sequence numbers, if the expected values are pre-calculated,
   the matched value must be appropriately recorded to detect lost