mLDP Extensions for Multi-Topology Routing
draft-ietf-mpls-mldp-multi-topology-09

Received changes through RFC Editor sync (changed state to RFC, created became rfc relationship between draft-ietf-mpls-mldp-multi-topology and RFC 9658, changed IESG state to RFC Published)

[Ballot comment]
Thanks for your work, I am clearing my DISCUSS. There’s one issue with the new text:

“The IGP Algorithm (IPA) Field Section 4.1.2 Section 6.1 is an 8-bit identifier for the algorithm. The permissible values are tracked in the IANA IGP Algorithm Types registry ([RFC9350] section 18.1.2).”

But, if I look at that reference, section 18.1.2 is “IGP Metric-Type Registry”. I won’t continue to hold a DISCUSS on this, I rely on the authors and responsible AD to make the correction.

[Ballot comment]
Question 11 on the shepherd writeup is incomplete.

The solitary SHOULD in this document is in Section 4.1.3, but it doesn't tell me why I might legitimately decide not to do what it says.

Nits:

* Section 5: s/Capaility/Capability/

* The syntax of the references in Sections 7.1 and 7.2 is curious.

* I don't think you need "(IANA)" in the diagram in Section 5.

[Ballot comment]
On further reflection, I have cleared my discuss; I would still like to see an answer, but am not holding it as a discuss

[Ballot comment]
# Gunter Van de Velde, RTG AD, comments for draft-ietf-mpls-mldp-multi-topology-05.txt

Please find https://www.ietf.org/blog/handling-iesg-ballot-positions/ documenting the handling of ballots.

Many thanks for the RTG_DIR reviews from Mike McBride, Yingzhen Qu and Gyan Mishra

#GENERIC COMMENTS
#================
##Text and concept is reasonably clear explained in the document, although in some sections i did get a slightly lost and had to search internet to understand the flow of formal procedures

## There are some potentially normative RFC2119 words in the document that are not capitalized.

#DETAILED COMMENTS
#=================

129   A more light weight mechanism to define constraint-based topologies
130   is the Flexible Algorithm (FA) [RFC9350].  FA can be seen as creating
131   a sub-topology within a topology using defined topology constraints
132   and computation algorithm.  This can be done within a MTR topology or
133   the default Topology.  An instance of such a sub-topology is
134   identified by a 1 octet value as documented in [RFC9350]).  Flexible
135   Algorithm is a mechanism to create a sub-topology, but in the future
136   different algorithms might be defined on how to achieve that.  For
137   that reason, in the remainder of this document, we'll refer to this
138   as the IGP Algorithm (IPA).

We should explicit mention the name of this field referenced above
as "identified by a 1 octet value" is the IGP Algorithm Types defined in RFC8665
where values 128-255 are reserved for IGP Flexible Algorithms. Maybe this can
be weaved into the text accordingly.
ref: https://www.iana.org/assignments/igp-parameters/igp-parameters.xhtml#igp-algorithm-types


170   The same applies to the IPA.  The IPA needs to be encoded as part of
171   the mLDP FEC to create unique MP-LSPs and at the same time is used to
172   signal to mLDP (hop-by-hop) which Algorithm needs to be used to
173   create the MP-LSP.

I find the term IPA slightly odd for a reader. It is one extra term used. Usage
of "IGP Algorithm Type" seems to read well and does not add so many letters
and does not add a new abbreviation. I understand that IPA is used in the
fields encoded and hence i assume it is used in this text blob.

180   Following subsections propose the extensions to bind an mLDP FEC to a
181   topology.  The mLDP MT extensions reuse some of the extensions
182   specified in [RFC7307].

What about following rewrite:
"The following subsections propose extensions to bind an mLDP FEC to a topology.
These mLDP MT extensions reuse some of the extensions specified in [RFC7307]."

202   Where "Root Node Address" encoding is as defined for given "Address
203   Family", and whose length (in octets) is specified by the "AF Length"
204   field.

this reads rather odd. Is this trying to say:
"The "Root Node Address" encoding is defined according to the given "Address Family," with
its length (in octets) specified by the "AF Length" field."

Is there need for normative language here?

206   To extend MP FEC elements for MT, the {MT-ID, IPA} is a tuple that is
207   relevant in the context of the root address of the MP LSP.  The {MT-
208   ID, IPA} tuple determines in which (sub)-topology the root address
209   needs to be resolved.  Since the {MT-ID, IPA} tuple should be
210   considered part of the mLDP FEC, the most natural place to encode
211   this tuple is as part of the root address.  While encoding it, we
212   also propose to use "MT IP" Address Families as described in
213   following sub section.

What about following readability rewrite. It also removes the "we":
"To extend MP FEC elements for MT, the {MT-ID, IPA} tuple is relevant in the
context of the root address of the MP LSP. This tuple determines the (sub)-topology
in which the root address needs to be resolved. As the {MT-ID, IPA} tuple should
be considered part of the mLDP FEC, it is most naturally encoded as part of the
root address. Additionally, we propose using "MT IP" Address Families as described
in the following subsection for this encoding.
"

211   this tuple is as part of the root address.  While encoding it, we
212   also propose to use "MT IP" Address Families as described in
213   following sub section.

I am not sure what this phrase is trying to say at this stage. Maybe i
got thrown of the rails by the usage of the word "propose". Is such statement not
requiring normative language?

217   [RFC7307] has specified new address families, named "MT IP" and "MT
218   IPv6", to allow specification of an IP prefix within a topology
219   scope.  In addition to using this address family for mLDP, we also
220   use 8 bits of the 16 bits Reserved field to encode the IGP Algorithm
221   (IPA) Registry.  The resulting format of the data associated with
222   these new Address Families is as follows:

I am not a fan of using the word "we" in formal procedures. It i sunclear who
is "we". (WG, IETF, authors, etc?)

What about following rewrite:
"[RFC7307] specifies new address families, named "MT IP" and "MT IPv6," to
allow for the specification of an IP prefix within a topology scope. In addition
to using these address families for mLDP, 8 bits of the 16-bit Reserved field
are utilized to encode the IGP Algorithm (IPA) Registry. The resulting format
of the data associated with these new Address Families is as follows:"

250       IPA: The IGP Algorithm, values are from the IGP Algorithm
251       registry.

This is almost correct. The registry is known as "IGP Algorithm Types"
https://www.iana.org/assignments/igp-parameters/igp-parameters.xhtml#igp-algorithm-types

258   By using extended MT IP Address Family, the resultant MT MP FEC
259   element is to be encoded as follows:

I suspect you are trying to say:

"By using the extended MT IP Address Family, the resulting MT MP FEC element
should be encoded as follows:
"

277   In the context of this document, the applicable LDP FECs for MT mLDP
278   include:

I had to look up where these code points were defined. AFter some searching was RC6388.
The RFC was previously suggested, but the reference here could maybe be more explite

288   *  Typed Wildcard FEC Element (type 0x5)

Here similar as previous code points. The reference rfc5918 would be helpfull
source: https://www.iana.org/assignments/ldp-namespaces/ldp-namespaces.xhtml#fec-type

290   In case of "Typed Wildcard FEC Element", the sub FEC Element type
291   MUST be one of the MP FECs listed above.

The figure 3 does not show the sub FEC Element type. Maybe a single phrase could be
added how it fits together high level. (i assume this may be well known in mLDP
environment though)

305   This document assumes the same definitions and procedures associated
306   with MPLS MT-ID as defined in [RFC7307] specification.

s/defined/specified/

310   "MT Multipoint Capability" is a new LDP capability, defined in
311   accordance with LDP Capability definition guidelines [RFC5561], that
312   is to be advertised to its peers by an mLDP speaker to announce its
313   capability to support MTR and the procedures specified in this
314   document.  This capability MAY be sent either in an Initialization
315   message at the session establishment time, or in a Capability message
316   dynamically during the lifetime of a session (only if "Dynamic
317   Announcement" capability [RFC5561] has been successfully negotiated
318   with the peer).

This text blob reads not naturally flowing.
What about the following readability re-edit, and i hope that i kept the
intended formal procedures intact:
"The "MT Multipoint Capability" is a new LDP capability, defined in accordance
with the LDP Capability definition guidelines outlined in [RFC 5561]. An mLDP
speaker advertises this capability to its peers to announce its support for MTR
and the procedures specified in this document. This capability MAY be sent
either in an Initialization message at session establishment or dynamically
during the session's lifetime via a Capability message, provided that
the "Dynamic Announcement" capability from [RFC 5561] has been
successfully negotiated with the peer.
"

339       Length: The length (in octets) of TLV.  The value of this field
340       MUST be 1 as there is no Capability-specific data [RFC5561] that
341       follows in the TLV.

There seems some word missing in "of TLV".
Maybe you intented to say:
"Length: This field specifies the length of the TLV in octets. The value
of this field MUST be 1, as there is no Capability-specific data [RFC 5561
following the TLV].
"

361   The MT extensions proposed in document do not require any extension
362   in procedures for Typed Wildcard FEC Element support [RFC5918], and
363   these procedures apply as-is to Multipoint MT FEC wildcarding.  Like

What does "proposed in document" mean? is potentially a word
missing (proposed in 'this' document")?

367   operations for MP FECs in the context of a given (sub)-topology as
368   identified by the MT-ID and IPA field.

As mentioned in an earlier observation the (sub)-topology is not displayed
in the figure5. WHere is the sub-topology corelated?

391       IPA: The IGP Algorithm, values are from the IGP Algorithm
392       registry.

The IANA registry is the "IGP Algorithm Types" registry to be
formally correct


399   [RFC5919] specifies extensions and procedures that allows an LDP
400   speaker to signal its End-of-LIB (i.e. convergence) for a given FEC
401   type towards a peer.  MT extensions for MP FEC do not require any
402   change in these procedures and they apply as-is to MT MP FEC
403   elements.  This means that an MT mLDP speaker MAY signal its
404   convergence per (sub-)topology using MT Typed Wildcard MP FEC
405   element.

I took liberty to add a little more context around End-of-LIB for
improved for readability. I hope it retains the original intent
of the authors:

"[RFC5919] specifies extensions and procedures that allow an LDP speaker
to signal its End-of-LIB for a given FEC type to a peer. By leveraging
the End-of-LIB message, LDP ensures that label distribution remains
consistent and reliable, even during network disruptions or maintenance
activities. The MT extensions for MP FEC do not require any modifications
to these procedures and apply as-is to MT MP FEC elements. Consequently, an
MT mLDP speaker MAY signal its convergence per (sub-)topology using
the MT Typed Wildcard MP FEC element."

445   To support LSP ping for MT Multipoint LSPs, this document uses
446   existing sub-types "P2MP LDP FEC Stack" and "MP2MP LDP FEC Stack"
447   defined in [RFC6425].  The proposed extension is to specify "MT IP"
448   or "MT IPv6" in the "Address Family" field, set the "Address Length"
449   field to 8 (for MT IP) or 20 (for MT IPv6), and encode the sub-TLV
450   with additional {MT-ID, IPA} information as an extension to the "Root
451   LSR Address" field.  The resultant format of sub-tlv is as follows:

I believe that the text should be more prescriptive. We are not longer
proposing an extension, but are providing the extension. A proposal implies
that that others may have other proposals to be considered, while that is
obviously not the intent. Hence maybe:

s/proposed/LSP Ping/

515 10.  Security Considerations

Should the security considerations of RFC7307 be mentioned?

522 11.  IANA Considerations

In section 9.1 there is suggestion of an implementation. Should the code
point used by that implementation not be suggested to be allocated by
IANA to avoid code-point squatting?

[Ballot discuss]
Be ye not afraid -- see
https://www.ietf.org/about/groups/iesg/statements/handling-ballot-positions/ on handling ballots, especially DISCUSS ballots...

I did not see a response to Linda Dunbar's Ops-Dir review - https://datatracker.ietf.org/doc/review-ietf-mpls-mldp-multi-topology-05-opsdir-early-dunbar-2024-05-03/
I have read the document, and am unable to figure out if the concern that she raised (""Each topology essentially multiplies the number of potential FECs needed, as separate FECs are necessary for the same network prefix across different topologies. [...]. It would be nice to add a Management Consideration section to address the compounded scalability concerns when each topology requires potentially unique FECs.") needs to be addressed in this document, or on another, or what.

Please note: I will happily clear this DISCUSS if the AD / chairs / authors / anyone tells me it's OK -- I really wasn't able to figure this out. Please treat this more of a "I want to make sure this had been considered" then an actual DISCUSS.

[Ballot discuss]
Thanks for this document. Overall I found it relatively easy to follow, at least as far as documents in the multicast space go. :-) I do have a couple of points I've entered as discusses, to make sure they don't get missed. I don't think these will be hard to resolve.

## DISCUSS

### Sections 4.1.2, 6.1, sources of IGP Algorithm values

These sections say, “IPA: The IGP Algorithm, values are from the IGP Algorithm registry”. But earlier on, the document talks about the IGP algorithm field as relating specifically to flexible algorithms. Flexible algorithms are not registered, other than the range 128-255 being marked as reserved in the registry. RFC 9350 section 4 specifically says that they are locally configured. So... are the values really from the registry?

Quite likely this only requires a small wording change, but I wanted to make sure I'm not missing some bigger issue.
 
### Section 4.1.3, unclear paragraph

I find it very difficult to understand what this paragraph is telling me to do:

  [RFC6514] defines the PMSI tunnel attribute for MVPN.  When the
  Tunnel Type is set to mLDP P2MP LSP, the Tunnel Identifier is a P2MP
  FEC Element.  When the Tunnel Type is set to mLDP Multipoint-to-
  Multipoint (MP2MP) LSP, the Tunnel Identifier is an MP2MP FEC
  Element.  For deploying mLDP in a network that supports MTR and FA,
  New MT MP FEC element SHOULD be used as the Tunnel Identifier.
 
To break down the paragraph, I think the first part:

  [RFC6514] defines the PMSI tunnel attribute for MVPN.  When the
  Tunnel Type is set to mLDP P2MP LSP, the Tunnel Identifier is a P2MP
  FEC Element.  When the Tunnel Type is set to mLDP Multipoint-to-
  Multipoint (MP2MP) LSP, the Tunnel Identifier is an MP2MP FEC
  Element. 
 
... is simply summarizing relevant information from RFC 6514?

            For deploying mLDP in a network that supports MTR and FA,
  New MT MP FEC element SHOULD be used as the Tunnel Identifier.

... well, I'm not confident that I know what that's telling me. MAYBE the whole thing could be rewritten something like this?

NEW:
  [RFC6514] defines the PMSI tunnel attribute for MVPN, and specifies
  that when the Tunnel Type is set to mLDP P2MP LSP, the Tunnel
  Identifier is a P2MP FEC Element, and when the Tunnel Type is set to
  mLDP Multipoint-to-Multipoint (MP2MP) LSP, the Tunnel Identifier is
  an MP2MP FEC Element.  When the extension defined in this
  specification is in use, the "IP MT-Scoped MP FEC Element Format"
  form of the respective FEC elements MUST be used in these two cases.
 
If that rewrite gets it wrong, please help me understand what you're trying to say.

Also, I have proposed using MUST and not SHOULD in my suggested rewrite. If you think SHOULD is the right keyword to use, please explain in what circumstances the correct behavior would be to use the legacy form of the identifier.

[Ballot comment]
## COMMENT

- This document should update RFC 7307, as a way of informing readers of RFC 7307 that the previously reserved half-field has been allocated and is no longer available. (That is, it should use the "Updates" header, mention in the abstract that it does, and briefly explain in the introduction, otherwise, idnits will complain.)

## NITS

- It's "IS-IS" and not "ISIS" (para 1 sec 2)

- Every place you use “propose“ you could, and probably should, rewrite it as “define“ or similar. The document is about to be an RFC, it’s no longer just a proposal.

[Ballot comment]
Thanks to Roni Evan for the GENART review.

** Per the GENART review:

-- Section 4.1.2
  In addition to using this address family for mLDP, we also
  use 8 bits of the 16 bits Reserved field to encode the IGP Algorithm
  (IPA) Registry.

Should RFC7307 be added to the document meta-data as being updated since the reserved fields are affected?

-- Section 4.1.3
  In the context of this document, the applicable LDP FECs for MT mLDP
  include:

  *  MP FEC Elements:

      -  P2MP (type 0x6)

      -  MP2MP-up (type 0x7)

      -  MP2MP-down (type 0x8)

Should this document be added to the following entries in the FEC Type Name Space registry (https://www.iana.org/assignments/ldp-namespaces/ldp-namespaces.xhtml#fec-type) as a reference?

** Section 6.1. Editorial.

      IPA: The IGP Algorithm, values are from the IGP Algorithm
      registry.

Provide a reference to the IGP Algorithms registry

[Ballot comment]
Many thanks to Christian Huitema's secdir review of this draft.  Please consider his recommendation for the Security Consideration section:

"The security section says that "This extension to mLDP does not introduce any
new security considerations beyond that already apply to the base LDP
specification [RFC5036], base mLDP specification [RFC6388], and MPLS security
framework [RFC5920]."

That may very well be true, but I would encourage the authors to examine at
least two risks: creating multiple topologies create additional work in the
"control plane", thus potential resource exhaustion if trying to support too
many topologies; traffic carried by multiple topologies may end up competing
for finite data plane resource, thus risking local overload. I am speculating,
but have the authors studied the corresponding failure modes? How hard is it
for configuration mistakes or adversarial actions to exploit such failure modes?"


Nits:

Glossary:  It would be easier if this was in some sort of alphabetical order (either by the acronym or the expansion). 

Missing from Glossary:  There are a bagillion undefined acronyms.  LIB, for example, which is not expanded anywhere that I can find, nor is it in the Editor's list.  Please consider adding those acronyms that are not contained here:  https://www.rfc-editor.org/materials/abbrev.expansion.txt

[Ballot comment]
GENERAL COMMENT:

Does this capability need to be configured, or is it enabled by default? If it needs to be configured, is there a plan to develop an augment to the YANG model to enable this capability?

Thanks to Roni Even for the General Area Review Team (Gen-ART) review. I do agree with his comments and would like to see the authors address it.
(https://mailarchive.ietf.org/arch/msg/gen-art/uETdASJBc4Pwq9qwkSA61R2MPvY).

-------------------------------------------------------------------------------
COMMENT
-------------------------------------------------------------------------------

Section 4.1.2, paragraph 8
>      Reserved: This 8-bit field MUST be zero on transmission and
>      ignored on receipt.

You mean to say "MUST be zero on transmission and MUST be ignored on receipt". Just make it explicit.

Section 4.1.3, paragraph 12
>    [RFC6514] defines the PMSI tunnel attribute for MVPN.  When the
>    Tunnel Type is set to mLDP P2MP LSP, the Tunnel Identifier is a P2MP
>    FEC Element.  When the Tunnel Type is set to mLDP Multipoint-to-
>    Multipoint (MP2MP) LSP, the Tunnel Identifier is an MP2MP FEC
>    Element.  For deploying mLDP in a network that supports MTR and FA,
>    New MT MP FEC element SHOULD be used as the Tunnel Identifier.

Do not see PMSI expanded anywhere in the document. Same for MVPN.

Found IP blocks or addresses not inside RFC5737/RFC3849 example ranges:
"2.4.1.2" and "2.4.1.1".

-------------------------------------------------------------------------------
NIT
-------------------------------------------------------------------------------

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.

"Abstract", paragraph 1
> h that when building a Multipoint LSPs(Label Switched Paths) it can follow a
>                                      ^
It appears that a white space is missing.

Section 1, paragraph 9
> to make LDP MT-aware and be able to setup unicast Label Switched Paths (LSPs)
>                                    ^^^^^
The verb "set up" is spelled as two words. The noun "setup" is spelled as one.

Section 1, paragraph 12
> ng IGP MT routing paths. A more light weight mechanism to define constraint-b
>                                ^^^^^^^^^^^^
Did you mean "lightweight"?

Section 2, paragraph 1
> on algorithm. This can be done within a MTR topology or the default Topology.
>                                      ^
Use "an" instead of "a" if the following word starts with a vowel sound, e.g.
"an article", "an hour".

Section 2, paragraph 2
> LDP) refers to extensions in LDP to setup multi-point LSPs (point-to-multipoi
>                                    ^^^^^
The verb "set up" is spelled as two words. The noun "setup" is spelled as one.

Section 2, paragraph 3
> oding so that LDP peers are able to setup an MP LSP via their own defined MTR
>                                    ^^^^^
The verb "set up" is spelled as two words. The noun "setup" is spelled as one.

Section 6.1, paragraph 2
> ies extensions and procedures that allows an LDP speaker to signal its End-o
>                                    ^^^^^^
Possible subject-verb agreement error detected.

Request for Last Call review by GENART Completed: Ready with Nits. Reviewer: Roni Even. Sent review to list. Submission of review completed at an earlier date.

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

IANA has completed its review of draft-ietf-mpls-mldp-multi-topology-05. If any part of this review is inaccurate, please let us know.

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

In the TLV Type Name Space Registry in the Label Distribution Protocol (LDP) Parameters registry group located at:

https://www.iana.org/assignments/ldp-namespaces/

a single new registration will be made as follows:

Value: [ TBD-at-Registration ]
Description: MT Multipoint Capability
Reference: [ RFC-to-be ]
Notes/Registration Date:

We understand that this is the only action required to be completed upon approval of this document.

NOTE: The action 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 action that will be performed.

For definitions of IANA review states, please see:

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

Thank you,

David Dong
IANA Services Sr. Specialist

The following Last Call announcement was sent out (ends 2024-05-02):

From: The IESG
To: IETF-Announce
CC: draft-ietf-mpls-mldp-multi-topology@ietf.org, james.n.guichard@futurewei.com, mpls-chairs@ietf.org, mpls@ietf.org, tsaad.net@gmail.com
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (mLDP Extensions for Multi-Topology Routing) to Proposed Standard


The IESG has received a request from the Multiprotocol Label Switching WG
(mpls) to consider the following document: - 'mLDP Extensions for
Multi-Topology Routing'
  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 2024-05-02. 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


  Multi-Topology Routing (MTR) is a technology to enable service
  differentiation within an IP network.  Flexible Algorithm (FA) is
  another mechanism of creating a sub-topology within a topology using
  defined topology constraints and computation algorithm.  In order to
  deploy mLDP (Multipoint label distribution protocol) in a network
  that supports MTR and/or FA, mLDP is required to become topology and
  FA aware.  This document specifies extensions to mLDP to support MTR
  with FA such that when building a Multipoint LSPs(Label Switched
  Paths) it can follow a particular topology and algorithm.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-mpls-mldp-multi-topology/



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

Request for posting confirmation emailed to previous authors: Anuj Budhiraja , Arkadiy Gulko , IJsbrand Wijnands , Mankamana Mishra , Syed Raza , Zhaohui Zhang , mpls-chairs@ietf.org

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?
[Ans]: The WG consensus represents broad agreement.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?
[Ans]: No.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize 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.)
[Ans]: No.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?
[Ans]: Yes, an implementations exist. See section 9 of the document.

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.
[Ans]: Yes, aspects of the solution leverage IGP extensions for flexible algorithm defined by
  SR and IGP/LSR WGs. The respective WGs were involved during the progress of the document
  and during the WGLC.
     
6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.
[Ans]: Yes, MPLS review team members reviewed before adoption by the WG. Further reviews by
the RTGDIR members and all comments were addressed.


7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] 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 [RFC 8342][5]?
[Ans]: Does not contain a YANG module.

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.
[Ans]: not applicable.

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?
[Ans]: this document defines extensions to allow MLDP to become topology and flex-algo
to enable service differentiation for multicast traffic over MPLS network. The shepherd
believes this is needed document, well written and ready to be handed off to the AD.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?
[Ans]: The RTGDIR was engaged to perform early review.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?
[Ans]: Proposed Standard.


12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.
[Ans]: A first IPR poll was done before adoption of the document. A second IPR poll was
done before WGLC.

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.
[Ans]: Currently, the document has 6 authors at the front page. Authors are associated with
different vendors and an operator.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)
[Ans]: Nits to be addressed.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].
[Ans]: None identified.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?
[Ans]: None.

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.
[Ans]: None.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?
[Ans]: None.

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.
[Ans]: No.

20. 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 aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).
[Ans]: the IANA section defines a new LDP capability parameter TLV for 'MT Multipoint
Capability'  and requests a new code point for the LDP TLV code point
be  assigned the lowest available value after 0x0500 from "TLV Type Name Space"
in the "Label Distribution Protocol (LDP) Parameters" registry within
"Label Distribution Protocol (LDP) Name Spaces".


21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.
[Ans]: yes. One registry:
"TLV Type Name Space" in the "Label Distribution Protocol (LDP) Parameters" registry within "Label Distribution Protocol (LDP) Name Spaces"

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://trac.ietf.org/trac/ops/wiki/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://trac.ietf.org/trac/iesg/wiki/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?
[Ans]: The WG consensus represents broad agreement.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?
[Ans]: No.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize 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.)
[Ans]: No.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?
[Ans]: Yes, an implementations exist. See section 9 of the document.

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.
[Ans]: Yes, aspects of the solution leverage IGP extensions for flexible algorithm defined by
  SR and IGP/LSR WGs. The respective WGs were involved during the progress of the document
  and during the WGLC.
     
6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.
[Ans]: Yes, MPLS review team members reviewed before adoption by the WG. Further reviews by
the RTGDIR members and all comments were addressed.


7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] 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 [RFC 8342][5]?
[Ans]: Does not contain a YANG module.

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.
[Ans]: not applicable.

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?
[Ans]: this document defines extensions to allow MLDP to become topology and flex-algo
to enable service differentiation for multicast traffic over MPLS network. The shepherd
believes this is needed document, well written and ready to be handed off to the AD.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?
[Ans]: The RTGDIR was engaged to perform early review.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?
[Ans]: Proposed Standard.


12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.
[Ans]: A first IPR poll was done before adoption of the document. A second IPR poll was
done before WGLC.

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.
[Ans]: Currently, the document has 6 authors at the front page. Authors are associated with
different vendors and an operator.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)
[Ans]: Nits to be addressed.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].
[Ans]: None identified.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?
[Ans]: None.

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.
[Ans]: None.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?
[Ans]: None.

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.
[Ans]: No.

20. 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 aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).
[Ans]: the IANA section defines a new LDP capability parameter TLV for 'MT Multipoint
Capability'  and requests a new code point for the LDP TLV code point
be  assigned the lowest available value after 0x0500 from "TLV Type Name Space"
in the "Label Distribution Protocol (LDP) Parameters" registry within
"Label Distribution Protocol (LDP) Name Spaces".


21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.
[Ans]: yes. One registry:
"TLV Type Name Space" in the "Label Distribution Protocol (LDP) Parameters" registry within "Label Distribution Protocol (LDP) Name Spaces"

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://trac.ietf.org/trac/ops/wiki/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://trac.ietf.org/trac/iesg/wiki/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/

Request for posting confirmation emailed to previous authors: Anuj Budhiraja , Arkadiy Gulko , IJsbrand Wijnands , Mankamana Mishra , Syed Raza , Zhaohui Zhang , mpls-chairs@ietf.org