IS-IS Extensions for Advertising Router Information
draft-ietf-isis-rfc4971bis-04

[Ballot comment]
Thank you for addressing my DISCUSS. I hope you can look at addressing comments as well:

1) In Section 4, 1st sentence: how can this specification have requirements on implementation that don't support this extension?

As per Alia:

RFC1195 says
"  Any codes in a received PDU that are not recognised shall be ignored
  and, for those packets which are forwarded (specifically Link State
  Packets), passed on unchanged."

So I think the document should mention RFC 1195 and don't use RFC 2119 keywords for something which is already stated there. For example:

OLD:

Routers that do not support the Router CAPABILITY TLV MUST silently
  ignore the TLV(s) and continue processing other TLVs in the same LSP.

NEW:

As per RFC 1195, routers that do not support the Router CAPABILITY TLV will silently
  ignore the TLV(s) and continue processing other TLVs in the same LSP.

2) It would be helpful if the document gave an example of multiple CAPABILITY TLVs containing non conflicting information and how it is to be handled.

3) Should subTLVs have an IANA registry? Or is there an existing one already?

[Ballot discuss]
I would like to get clarification on the following points before recommending approval of this document:

1)
Section 2 says:
  The Router CAPABILITY TLV is OPTIONAL.  As specified in Section 3,
  more than one Router CAPABILITY TLV from the same source MAY be
  present.

Section 3 says:

  Where a receiving system has two copies of a CAPABILITY TLV from the
  same system that have different settings for a given attribute, the
                                                  ^^^^^^^^^^^^^^^
  procedure used to choose which copy shall be used is undefined.

The word "attribute" only occurs once in the document, so it would be better if it is replaced for clarity. Does "a given attribute" mean "a single sub-TLV" or "all sub-TLVs included in a CAPABILITY TLV instance"?

If "a given attribute" means "a single sub-TLV", then I have the following followup questions:

What happens in real world if there are two CAPABILITY TLVs which contain different attributes? Are they treated as cumulative (i.e. this is a nice trick to overcome CAPABILITY TLV length limit), does the second CAPABILITY  TLV value always overrides earlier instances of the CAPABILITY TLV?

I think the document should state what happens. If there is no consistent behaviour in this area, the document should says so as well.

[Ballot comment]
I know this is a bis doc that mainly clarifies one point. However, as there were also other smaller updates, here are some additional comments that could be considered:

1) To me the text in section 2 reads like: if S is not set D should be ignored. Is this correct? If so, it could be spelled out like this. If not, what happens if S is not set but D is?

2) The text says: „Where a receiving system has two copies of a CAPABILITY TLV from the
  same system that have different settings for a given attribute, the
  procedure used to choose which copy shall be used is undefined.“
  Why is there no default given here? Not defining something like this can lead to problems. I would strongly recommend to define a default behavior.

3) Further it says: „How partial support may impact the operation of the
  capabilities advertised within the Router CAPABILITY TLV is outside
  the scope of this document.“
  While it might be true that this is specific to the capability, I would put a MUST requirement in here for future specifiactions: Partial suport MUST be defined in the document that describes the subTLV.

4) On this sentence: „Routers that do not support the Router CAPABILITY TLV MUST silently
  ignore the TLV(s) and continue processing other TLVs in the same LSP.“
  What does "silently" mean here? Is it not allowed to log such an event? I would recommend to either clarify that "silently" means here or remove that word.

5) In this sentence: "If leaking of the CAPABILITY TLV is required, the entire CAPABILITY
  TLV MUST be leaked into another level without change even though it
  may contain some sub-TLVs which are unsupported by the Router doing
  the leaking.“
  I would recomend to use the normative language differently to be clear about what it applies to:
"If leaking of the CAPABILITY TLV is required, the entire CAPABILITY
  TLV MUST NOT change sub-TLVs which are unsupported by the Router doing
  the leaking.“

6) In section 5: „Note that an integrity mechanism, such as the one
  defined in [RFC5304] or [RFC5310], should be applied if there is high
  risk resulting from modification of capability information.“
  Why is that a SHOULD and what's a „high risk“?  It should me either "MUST be applied at high risk" and defining what a high risk is, or it should be "SHOULD be applied at (any) risk".

[Ballot comment]
I know this is a bis that mainly clarifies one point. However, as there were also other smaller updates, here are some additional comments that could be considered:

1)

[Ballot discuss]
* Section 4 requires the CAPABILITY TLV to be leaked without any change based on the text below

"If leaking of the CAPABILITY TLV is required, the entire CAPABILITY TLV MUST be leaked into another level without change even though it may contain some sub-TLVs which are unsupported by the Router doing the leaking. "

but Section 2 requires a router leaking the TLV from level-2 to level-1 to set the D bit and this violates the "without change" requirement.

I think this inconsistency needs to be resolved somehow.

P.S.: One possible way would be to add some exception text for the D bit into the above text in Section 4. Another would be to remove the restriction against change (I noticed that this restriction did not exist in RFC4971 - was this check added to fix some issue identified during deployment?).

[Ballot comment]
The first sentence in section 4 says:

  Routers that do not support the Router CAPABILITY TLV MUST silently
  ignore the TLV(s) and continue processing other TLVs in the same LSP.

Is this the authoritative text for a new requirement, or is that preexisting behavior defined elsewhere? If the former, why would we expect an implementation that does not implement this spec (perhaps the implementors haven't read it) to honor this requirement? If the latter, then please state it descriptively (i.e. without 2119 keywords), preferably with a citation.

[Ballot discuss]
I would like to get clarification on the following points before recommending approval of this document:

1) How do multiple CAPABILITY TLVs from the same source treated, if they have the same S and D flags, but different subTLV? Are the cumulative? Or this is not allowed?
I am sorry if I missed where this was described, let me know if I did.

[Ballot comment]
1) In Section 4, 1st sentence: how can this specification have requirements on implementation that don't support this extension?

As per Alia:

RFC1195 says
"  Any codes in a received PDU that are not recognised shall be ignored
  and, for those packets which are forwarded (specifically Link State
  Packets), passed on unchanged."

So I think the document should mention RFC 1195 and don't use RFC 2119 keywords for something which is already stated there. For example:

OLD:

Routers that do not support the Router CAPABILITY TLV MUST silently
  ignore the TLV(s) and continue processing other TLVs in the same LSP.

NEW:

As per RFC 1195, routers that do not support the Router CAPABILITY TLV will silently
  ignore the TLV(s) and continue processing other TLVs in the same LSP.

2) Should subTLVs have an IANA registry? Or is there an existing one already?

[Ballot discuss]
I would like to get clarification on the following points before recommending approval of this document:

1) How do multiple CAPABILITY TLVs from the same source treated, if they have the same S and D flags, but different subTLV? Are the cumulative? Or this is not allowed?
I am sorry if I missed where this was described, let me know if I did.

2) In Section 4, 1st sentence: how can this specification have requirements on implementation that don't support this extension? If this behaviour is already prescribed by another specification, then you should not use RFC 2118 keyword and you should reference the relevant specification.

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

IANA has completed its review of draft-ietf-isis-rfc4971bis-01.txt. If any part of this review is inaccurate, please let us know.

IANA has a question about one of the actions requested in the IANA Considerations section of this document.

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

In section 6 of the current draft, the authors state: "IANA assigned a new IS-IS TLV code-point for the newly defined IS-IS TLV type named the IS-IS Router CAPABILITY TLV and defined in this document. The assigned value is 242."

IANA notes that this registration was completed by RFC4971.

IANA Question --> Do the authors wish that the reference for the registatiion of the CAPABILITY TLV be updated to [ RFC-to-be ] or should it be left as RFC4971?

IANA 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 only to confirm what actions will be performed. 

Thank you,

Sabrina Tanamal
IANA Specialist
ICANN

The following Last Call announcement was sent out:

From: The IESG
To: "IETF-Announce"
CC: isis-chairs@ietf.org, isis-wg@ietf.org, chopps@chopps.org, akatlas@gmail.com, "Christian Hopps" , draft-ietf-isis-rfc4971bis@ietf.org
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (IS-IS Extensions for Advertising Router Info) to Proposed Standard


The IESG has received a request from the IS-IS for IP Internets WG (isis)
to consider the following document:
- 'IS-IS Extensions for Advertising Router Info'
  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
ietf@ietf.org mailing lists by 2016-08-15. 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 defines a new optional Intermediate System to
  Intermediate System (IS-IS) TLV named CAPABILITY, formed of multiple
  sub-TLVs, which allows a router to announce its capabilities within
  an IS-IS level or the entire routing domain.





The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-isis-rfc4971bis/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-isis-rfc4971bis/ballot/


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

PROTO Questionaire and Write-up for: draft-ietf-isis-rfc4971bis-02

    (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:

    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.

This document updates RFC4971 and clarifies the Router ID sub-TLV content as
well as defines a use for the previously reserved 0.0.0.0 value. This is to
allow for IPv6 only deployments.

    Working Group Summary:

    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?

The consensus was strong.

    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?

There are multiple implementations of these changes.

    Personnel:

    Who is the Document Shepherd? Who is the Responsible Area Director?

Shepherd: Christian Hopps
AD: Alia Atlas

    (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 important modified text is one paragraph and has been reviewed by the
shepherd.

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

No.

    (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.

None.

    (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?

Strong with the active participants.

    (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.

None.

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

None 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?

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.

Will update and replace RFC4971.

    (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).

No changes made here.

    (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.

No changes made here.

    (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.

NITs from datatracker are OK.