Oh, coming to this late.

Can we not “ERO object”?

Otherwise we condense it to “EROO” which leads to “EROO object” and so to
“EROOO” etc. :-)

 

Adrian

--

Tales from the Wood

Four volumes of fairy tales for adults of all ages

Buy them in Shenzhen direct from me

 

 

From: Italo Busi <[email protected]> 
Sent: 11 March 2026 08:47
To: Samuel Sidor (ssidor) <[email protected]>; [email protected]
Cc: [email protected]; [email protected]
Subject: RE: draft-ietf-pce-multipath-19 early Opsdir review

 

Hi Samuel,

 

I am fine with the changes in the -20 version

 

Just a minor of possible editorial improvements to section 1.2:

 

1.      In the definition of Segment List: c/ERO object/ERO or RRO object/
(for consistency with the definition of path above and the rest of the
document)
2.      Add a definition also for RRO and expand the acronym at first use

 

Italo

 

From: Samuel Sidor (ssidor) <[email protected] <mailto:[email protected]> > 
Sent: sabato 28 febbraio 2026 03:14
To: Italo Busi <[email protected] <mailto:[email protected]> >;
[email protected] <mailto:[email protected]> 
Cc: [email protected]
<mailto:[email protected]> ; [email protected]
<mailto:[email protected]> 
Subject: Re: draft-ietf-pce-multipath-19 early Opsdir review

 

Hi Ital,

 

Please check updated version of the draft. It is addressing comments from
multiple mail threads, so the diff is not small.

 

Thanks a lot,

Samuel

 

From: Samuel Sidor (ssidor) <[email protected] <mailto:[email protected]> >
Date: Tuesday, 24 February 2026 at 15:12
To: Italo Busi <[email protected] <mailto:[email protected]> >,
[email protected] <mailto:[email protected]>  <[email protected]
<mailto:[email protected]> >
Cc: [email protected]
<mailto:[email protected]>
<[email protected]
<mailto:[email protected]> >, [email protected]
<mailto:[email protected]>  <[email protected] <mailto:[email protected]> >
Subject: Re: draft-ietf-pce-multipath-19 early Opsdir review

Thanks a lot, Italo.

 

I'll submit updated version 20 after concluding on comments from Adrian
(parallel mailing list).

 

Regards,

Samuel

 

From: Italo Busi <[email protected] <mailto:[email protected]> >
Date: Tuesday, 24 February 2026 at 14:56
To: Samuel Sidor (ssidor) <[email protected] <mailto:[email protected]> >,
[email protected] <mailto:[email protected]>  <[email protected]
<mailto:[email protected]> >
Cc: [email protected]
<mailto:[email protected]>
<[email protected]
<mailto:[email protected]> >, [email protected]
<mailto:[email protected]>  <[email protected] <mailto:[email protected]> >
Subject: RE: draft-ietf-pce-multipath-19 early Opsdir review

Hi Samuel,

 

Thanks for your prompt feedbacks

 

I think that your proposed changes fully address my comments

 

Italo

 

From: Samuel Sidor (ssidor) <[email protected] <mailto:[email protected]> >
Sent: martedì 24 febbraio 2026 14:04
To: Italo Busi <[email protected] <mailto:[email protected]> >;
[email protected] <mailto:[email protected]> 
Cc: [email protected]
<mailto:[email protected]> ; [email protected]
<mailto:[email protected]> 
Subject: Re: draft-ietf-pce-multipath-19 early Opsdir review

 

Hi Italo,

 

Thanks a lot for your review.

 

Please see inline <S>.

 

Regards,

Samuel

 

From: Italo Busi via Datatracker <[email protected] <mailto:[email protected]>
>
Date: Wednesday, 18 February 2026 at 16:20
To: [email protected] <mailto:[email protected]>  <[email protected]
<mailto:[email protected]> >
Cc: [email protected]
<mailto:[email protected]>
<[email protected]
<mailto:[email protected]> >, [email protected]
<mailto:[email protected]>  <[email protected] <mailto:[email protected]> >
Subject: draft-ietf-pce-multipath-19 early Opsdir review

Document: draft-ietf-pce-multipath
Title: Path Computation Element Communication Protocol (PCEP) Extensions for
Signaling Multipath Information Reviewer: Italo Busi Review result: Ready

Hi,

I have been selected as the Operational Directorate (opsdir) reviewer for
this
Internet-Draft.

The Operational Directorate reviews all operational and management-related
Internet-Drafts to ensure alignment with operational best practices and that
adequate operational considerations are covered.

A complete set of _"Guidelines for Considering Operations and Management in
IETF Specifications"_ can be found at
https://datatracker.ietf.org/doc/draft-ietf-opsawg-rfc5706bis/.

While these comments are primarily for the Operations and Management Area
Directors (Ops ADs), the authors should consider them alongside other
feedback
received.

- Document: draft-ietf-pce-multipath-19

- Reviewer: Italo Busi

- Review Date: 17 February 2026

- Intended Status: Standards Track

---

## Summary

- Has Issues: I have some minor concerns about this document that I think
should be resolved before publication.

## General Operational Comments Alignment with RFC 5706bis

This document defines a mechanism for signaling multi-path LSPs using PCEP,
including also a mechanisms for the PCE speakers to exchange information
about
their capabilities in support of multi-path LSPs.

Although the primary focus is the support of SR Candidate Path with more
than
one Segment List, the solution is generic and this generalization is clearly
stated in the scope and introduction of the document.

The document does not strictly follow the RFC5706bis guidelines, although
the
Manageability Considerations section (section 10) provides sufficient
guidelines for operating the protocol extensions defined in the document and
it
is aligned with RFC6123.

## Major Issues

No major issues found.

---

## Minor Issues

These comments are mainly editorial and intended to clarify (e.g., making it
more explicit) some interpretations of the current text based on my
understanding.

1) Section 3.4

OLD

   This TLV is used to specify protecting standby path(s), for each ECMP
   path within a PCEP LSP.  This is similar to path protection, but
   works at the ECMP path level instead of at the PCEP LSP level.

NEW

   This TLV is used to describe a set of backup path(s) protecting a
   primary path within a PCEP LSP: see Section 4.4 for details.  This
   is similar to path protection, but works at the ECMP path level
   instead of at the PCEP LSP level.

Without the clarification text in section 4.4 it was very hard for me to
understand how this TLV could be used by just reading this section.

 

<S> I'll update it.

2) Section 3.5

Can N and L bits be set independently in the MULTIPATH-OPPDIR-PATH TLV?

I think that a link co-routed path is also node co-routed. One option is to
be
liberal and ignore N when L is set. Another option is to force that N is
also
set when L is set.

It would be better if the document is explicit about this point.

<S> Thanks, Adrian (document shepherd) raised same comment, this is proposed
text:

 

* N (Node co-routed): If set, indicates this path is

node co-routed with its opposite direction path, specified in this TLV.

Two opposite direction paths are node co-routed if they

traverse the same nodes, but MAY traverse different links.

If not set, the paths are not guaranteed to be node co-routed

(they may or may not traverse the same set of nodes).

 

* L (Link co-routed): If set, indicates this path is

link co-routed with its opposite direction path, specified in this TLV.

Two opposite direction paths are link co-routed if they

traverse the same links (but in opposite directions).

Link co-routing implies node co-routing; therefore, it is not

necessary to set the N flag when the L flag is set

 

Are you fine with that?

3) Section 3.5

Is there any difference between reporting a MULTIPATH-OPPDIR-PATH TLV with
Opposite Direction Path ID set to zero or not reporting the
MULTIPATH-OPPDIR-PATH TLV at all?

 

<S>Both should indicate same thing. I'll add statement to clarify and I'll
try to double confirm with other co-authors (in case if it was intended to
be used as indication that for example PCE tried to compute reverse path,
but failed to find it).

4) Section 4.1.1

OLD

   New MULTIPATH-CAP TLV is defined.  This TLV MAY be present in the
   OPEN object during PCEP session establishment.

NEW

   New MULTIPATH-CAP TLV is defined.  This TLV MAY be present in the
   OPEN object during PCEP session establishment.  It MAY also be
   present in the LSP object for each individual LSP from the PCC.

The proposal is to keep the first paragraph consistent with the rest of the
section.

<>Ack, I'll update it.

5) Section 4.1.1

OLD

   *  O-flag: whether MULTIPATH-OPPDIR-PATH TLV is supported and
      requested.  If this flag is set, the PCE SHOULD tell the PCC the
      reverse path information, if it is able to.

NEW

   *  O-flag: whether MULTIPATH-OPPDIR-PATH TLV is supported by the PCE
      or requested by the PCC.  If this flag is set by the PCC, the PCE
      SHOULD tell the PCC the reverse path information, if it is able
      to.

If my understanding is correct, it would be useful to be more explicit as
proposed above.

 

<S> I assume that your proposed text is not fully covering PCE-initiated
LSPs (e.g. consider one PCE creating that LSP, which will be later
re-delegated to other PCE for path-computation).

 

What about:

 

 * O-flag: In the OPEN object, this flag indicates whether the 

MULTIPATH-OPPDIR-PATH TLV is supported. In the LSP object, this flag 

indicates that opposite-direction path information is requested or provided 

for that specific LSP. When set by the PCC (in PCRpt/PCReq), it requests 

the PCE to provide reverse path information. When set by the PCE (in 

PCInit/PCUpd/PCRep), it indicates the PCE is providing or will provide 

reverse path information. In both cases, the PCE SHOULD provide the reverse 

path information, if it is able to.

6) Section 4.1.1

OLD

   When PCE computes the LSP path, it MUST NOT return more forward
   multipaths than the corresponding value of "Number of Multipaths"
   from the MULTIPATH-CAP TLV.  <...>

NEW

   When PCE computes the LSP path, it MUST NOT return more forward
   multipaths than the corresponding value of "Number of Multipaths"
   in the MULTIPATH-CAP TLV received from the PCC.  <...>

If my understanding is correct, it would be useful to be more explicit as
proposed above.

<S> There was already suggestion from Adrian to change it to:

 

When a PCE computes an LSP path, it MUST NOT return more forward 

multipaths than the minimum of the "Number of Multipaths" values 

advertised by both the PCE and PCC in their respective MULTIPATH-CAP TLVs 

during capability negotiation.

 

Are you fine with that version as well?



7) Section 4.1.1

The last paragraph seems an example associated with the third to last
paragraph
and not with the penultimate paragraph.

I would suggest to swap the order of the last two paragraphs.

<S> Ack, I'll change it.

---

## Nits

Optional editorial suggestions (e.g., acronym expansions or grammar fixes).

1) Section 4.3: please expand PLSP on first use.

- Example:

 > Abstract: Expand "NFV" on first use.

 > Section 3.1: "it’s" -> "its".

<S> Thanks, I"ll fix those.

No minor issues found.

---

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